Ford's new 6.2 liter 400 hp gas engine.

[Dogmeat]

dog, what gear ratio you have on your 8.1? mine(suburban) with 3.73 got noticable better then my buddies with 4.10 gears(about 2 mpg better on average).....and pretty much still pull bumper to bumper up the hills up to 10000 pds hooked on the back.....

2005 8.1L/Allison 2500 HD, ECSB .... 3.73 gears, 265/75/16 BFG Load Range E tires ... computer properly programmed for larger tire size.

This combination usually gets me right around 15 mpg on the highway at 65 mph, if I set the cruise on 75 it goes down to about 13.5-14 ...

When I first bought the truck I put a set or 285/75/16 Nitto Terra Grapplers on it .... I was getting slightly worse mileage with the larger 285 tires, maybe 14.5 mpg @ 65 and 13 @ 75 .... going to the smaller tire size did improve my mileage a little bit ... made no difference whatsoever when I had a trailer hooked up to it .... I got 9.5 mpg with the 285 nittos, I get 9.5 mpg with the 265 BFG's ...

I get the same mileage pulling the same enclosed trailer as I did with my 2000 5.3L chevy .....

I get 9.5 MPG pulling my little 16' 2-place enclosed that weighs at most about 4,000-lb fully loaded, I get 9.5 MPG pulling my dad's 26' Charmac enclosed .... I get 10 mpg pulling my little open 2-place 4-wheeler trailer ....

I swear, it's like as soon as you tack a trailer onto this thing, it doesn't matter how big the trailer is, it just gets 9.5-10 mpg ....

I have gotten as bad as 7.2 mpg with it ... but that was pulling that 26' charmac down I80 on a royally windy day at 80 mph too .....

I mean the moral of the story is, you aren't going to win any fuel economy awards owning a gas motor and towing a trailer with it, be it 5.3L, 5.4L, 6.0L, 6.2L, 6.8L, 8.1L, etc ..... the moral of the story is that buying a diesel to tow a smaller trailer, meaning probably a sub 6,000-lb trailer might not be the most economical choice if you actually put the numbers to it ...

With that said, if GM still offered the 8.1L in their trucks I wouldn't mind owning another one, I just wish they'd put 44 gallon tanks in them

 

[AKSNOWRIDER]

2005 8.1L/Allison 2500 HD, ECSB .... 3.73 gears, 265/75/16 BFG Load Range E tires ... computer properly programmed for larger tire size.

This combination usually gets me right around 15 mpg on the highway at 65 mph, if I set the cruise on 75 it goes down to about 13.5-14 ...

When I first bought the truck I put a set or 285/75/16 Nitto Terra Grapplers on it .... I was getting slightly worse mileage with the larger 285 tires, maybe 14.5 mpg @ 65 and 13 @ 75 .... going to the smaller tire size did improve my mileage a little bit ... made no difference whatsoever when I had a trailer hooked up to it .... I got 9.5 mpg with the 285 nittos, I get 9.5 mpg with the 265 BFG's ...

I get the same mileage pulling the same enclosed trailer as I did with my 2000 5.3L chevy .....

I get 9.5 MPG pulling my little 16' 2-place enclosed that weighs at most about 4,000-lb fully loaded, I get 9.5 MPG pulling my dad's 26' Charmac enclosed .... I get 10 mpg pulling my little open 2-place 4-wheeler trailer ....

I swear, it's like as soon as you tack a trailer onto this thing, it doesn't matter how big the trailer is, it just gets 9.5-10 mpg ....

I have gotten as bad as 7.2 mpg with it ... but that was pulling that 26' charmac down I80 on a royally windy day at 80 mph too .....

I mean the moral of the story is, you aren't going to win any fuel economy awards owning a gas motor and towing a trailer with it, be it 5.3L, 5.4L, 6.0L, 6.2L, 6.8L, 8.1L, etc ..... the moral of the story is that buying a diesel to tow a smaller trailer, meaning probably a sub 6,000-lb trailer might not be the most economical choice if you actually put the numbers to it ...

With that said, if GM still offered the 8.1L in their trucks I wouldn't mind owning another one, I just wish they'd put 44 gallon tanks in them

actually they do ..you have choices here..the suburbans came with two tanks..1 in the rear transfers to the frt tank which the motor runs off(as do the bigger work trucks we have..suburban tanks are 28-29 frt tank 10-11 rear tank, our work trucks run any combo from 50 frt and rear down to 26 frt and 20 rear...all factory parts and a reflash for the work truck ecu programming and your good to go..you will loose your spare tire mnt in the back though..I did 2 customer pickups this way and they work excellent...used all factory parts including fuel lines, brackets, emission lines, canisters and even emission stickers(put thru our Im program for aproval which is based on california emissions standards and they passed )once everything was installed ran it down to our local gm dealer and had them reflashed....

 

[Dogmeat]

actually they do ..you have choices here..the suburbans came with two tanks..1 in the rear transfers to the frt tank which the motor runs off(as do the bigger work trucks we have..suburban tanks are 28-29 frt tank 10-11 rear tank, our work trucks run any combo from 50 frt and rear down to 26 frt and 20 rear...all factory parts and a reflash for the work truck ecu programming and your good to go..you will loose your spare tire mnt in the back though..I did 2 customer pickups this way and they work excellent...used all factory parts including fuel lines, brackets, emission lines, canisters and even emission stickers(put thru our Im program for aproval which is based on california emissions standards and they passed )once everything was installed ran it down to our local gm dealer and had them reflashed....

What trucks can you still get the 8.1L in? The Suburban and Avalanche are all ...? I tried the "build your own silverado" on a 2010 truck the other day and the 8.1L was not an option on 3/4 or 1-ton pickups ...

That is a badass idea, I had no idea you could set the fuel tanks up like that. I have been looking at doing a TransferFlow 44-gallon replacement tank or their 30-gallon tank/toolbox combination .... I wonder if I could save any money doing the GM factory setup? I'll have to look into that ...

 

[AKSNOWRIDER]

What trucks can you still get the 8.1L in? The Suburban and Avalanche are all ...? I tried the "build your own silverado" on a 2010 truck the other day and the 8.1L was not an option on 3/4 or 1-ton pickups ...

That is a badass idea, I had no idea you could set the fuel tanks up like that. I have been looking at doing a TransferFlow 44-gallon replacement tank or their 30-gallon tank/toolbox combination .... I wonder if I could save any money doing the GM factory setup? I'll have to look into that ...

unfortunately the 8.1 is gone....we have them in our work trucks..along with the d-max and some fords..(c-6500's up to 18 ft. flatbeds)..price wise ..last one I did was in 2003 and it ran about 1200 in parts(but this is alaska and we pay out the nose, and that was every peice to meet our IM program and get certified legal)but it is a pretty straight forward install...

 

[mattymac]

the big diffrence in the 8.1 (or anything naturally asperated) is towing in high altitude over a turbo diesel. The hp loss sucks!

but im towing with a 450-500hp (600 empty) 04 cummins so bring on these gas motors!


Whats the 8.1 hp wise? wasnt it 340?

 

[Ford428CJ]

the big diffrence in the 8.1 (or anything naturally asperated) is towing in high altitude over a turbo diesel. The hp loss sucks!

but im towing with a 450-500hp (600 empty) 04 cummins so bring on these gas motors!


Whats the 8.1 hp wise? wasnt it 340?

Besides that... Diesels are much more efficient over gas. And make more Tq.... That's what gets you there LOL

 

[Transporter]

My tractor has like 125hp and I bet it can out pull any of your guys 400 --500 hp trucks.

 

[summitboy]

Not true. If it is anything like gm's 8.1 they were right with the deisels for milage when LOADED. Sure, empty the deisels get better milage, but loaded, is a different story. Alot like the good ol 460's. 10 mpg empty, 10 mpg hauling everything but the kitchen sink behind you. My Dad's 8.1 only gets about 13-14 empty, but still gets 9 pulling a 25' fith wheel with a 20' boat behind it! And loaded like that, will pull a grade with any stock deisel. For the record, I have a 7.3 powerstroke and have had it for several years. I can't say it has been a bad truck, but I am not convinced that they are the best way to go either. My next truck will be a gasser. No more $100+ oil changes, and all the other things that go with the deisels. Going round and round at the gas station to fuel the truck AND the toys. Lots of little things.

LOL, 9 mpg. I used to pull a 26 5ver with my 5000lb Super Air Nautique behind it and can easily get 15-16mpg (hand calculated). That was before my mods which get me even better mileage than stock. Empty I see between 21-23 mpg hand calculated. Gas may be great for driving around town getting groceries but when it comes to towing, $100 oil changes are well worth the pulling power and fuel mileage.

 

[Dogmeat]

Besides that... Diesels are much more efficient over gas. And make more Tq.... That's what gets you there LOL

They aren't that much more effecient, maybe %28 compared to %26 of a modern small block gas motor. It's literally less than a %4 difference in actual real world practice.

I've done the math on this, trust me ... that's why I keep stating my argument, over continuous heavy-load conditions diesel motors are better. For personal use they are rarley justified as far as cost goes, unless you're just completley unable to deal with not having the most powerful motor you can get in a pickup truck.

 

[Ford428CJ]

They aren't that much more effecient, maybe %28 compared to %26 of a modern small block gas motor. It's literally less than a %4 difference in actual real world practice.

I've done the math on this, trust me ... that's why I keep stating my argument, over continuous heavy-load conditions diesel motors are better. For personal use they are rarley justified as far as cost goes, unless you're just completley unable to deal with not having the most powerful motor you can get in a pickup truck.

Don't take this to hart....

I'm not saying that diesel dont cost you money to run. Not the case! Nor am I trying to justify the maintenance for one. Unless you work it all the time.

BUT if we are comparing engine to engine, YES diesels are more then 4% efficiency difference! If you put your small block in my P/U (that weights 8,000 pound Crew Cab and lifted with 35's on it) wouldn't come close to the same mileage! Besides that gas has a lower BTU's of heat when compared to Diesel fuel. That = working energy.

Since your small block is in a lighter weight P/U compared to mine, the difference in mileage may not be a big difference. And maintenance cost (on gas) are way less (besides fuel cost, difference in regular to diesel fuel). JMHO

 

[Dogmeat]

Don't take this to hart....

I'm not saying that diesel dont cost you money to run. Not the case! Nor am I trying to justify the maintenance for one. Unless you work it all the time.

BUT if we are comparing engine to engine, YES diesels are more then 4% efficiency difference! If you put your small block in my P/U (that weights 8,000 pound Crew Cab and lifted with 35's on it) wouldn't come close to the same mileage! Besides that gas has a lower BTU's of heat when compared to Diesel fuel. That = working energy.

Since your small block is in a lighter weight P/U compared to mine, the difference in mileage may not be a big difference. And maintenance cost (on gas) are way less (besides fuel cost, difference in regular to diesel fuel). JMHO

The math would say otherwise.

This is for an ideal air-standard Otto cycle ... meaning, no mechanical losses, losses due to heat transfer, anything ... in a PERFECT world, a spark ignition engine (otto cycle) would approach a MAXIMUM effeciency of ~%67.

Here is the same curve for a Diesel cycle:

So you can see that for a given compression ratio of ~16:1 which is in the neighborhood of what most modern diesels operate, in a PERFECT WORLD the absolute maximum effeciency you could possibly acheive would be approximatley %56 .....

For a spark ignition gasoline motor operating at a compression ratio of 10:1, the effeciency level is is roughly the same ....

The reason diesel-cycle motors are slightly more effecient int he real world is due to the fact that there is no throttleing of the air charge filling the cylinders .... there is no restriction in this way such as on a gas motor. This is also why you can "hop up" your diesel by simply adding more fuel at whatever engine speed you are running at, becuase you take a "full" charge of air in every stroke.

As far as mechanical effeciency goes, that's really it .... there is nothing about diesel motors that makes them inherently more effecient or reliable than a gas motor other than there is no restriction from the throttling process.

I mean really, if diesel motors saved us that much money we'd still be running them for our fleet. I have done some pretty in-depth economic analysis of this and I cannot for the life of me find any condition whatsoever that you are actually saving money in what is the typical lifespan of a modern day pickup truck by buying a diesel UNLESS you are literally towing 10,000-lbs around with you every time you turn the motor on.

Call it what you want to, but the only advantages to buying a diesel truck are power and range. That's it .... given those are two nice things to have, but you are completley fooling yourself if you think you're saving money buying a diesel truck for personal use.

 

[ruffryder]

I have done some pretty in-depth economic analysis of this and I cannot for the life of me find any condition whatsoever that you are actually saving money in what is the typical lifespan of a modern day pickup truck by buying a diesel UNLESS you are literally towing 10,000-lbs around with you every time you turn the motor on.

You mind giving some specifics of your example? I don't doubt you at all. Just curious as to the specifics of what you used. I am a geek like that.

 

[Dogmeat]

You mind giving some specifics of your example? I don't doubt you at all. Just curious as to the specifics of what you used. I am a geek like that.

I can't post the actual spreadsheets we use in conjunction with data from our leasing company because it's company property ....

But basically what it amounted to is that when you take into account the additional capital costs of buying a diesel truck, assuming a service life of 100,000 miles, all the maintenence costs, fuel costs, etc, we found that there was assuredly no cost savings whatsoever to owning or leasing fleets of diesel trucks as opposed to gas trucks. The major kicker on this, which revolved mainly around the Ford 6.0L believe it or not, was that we had more trouble with that diesel than ANY other motor we had. We have completley gotten rid of diesel motors even in our F450 service trucks because they were totally unreliable.

When you factor in depreciation, the diesel trucks do tend to hold their value better than a gasoline motor truck does, but this is primarily due to the fact that they cost more to buy than anything else ... not necessarily 'because it's a diesel' .... we factored in depreciation, insurance, all kinds of costs ....

I made myself a VERY basic spreadsheet for keeping these costs nearly 10 years ago. When you break vehicle costs down into average $/mile, it becomes readily apparent which vehicles are costing you the most ...

Typically, and like I said I'm not against Ford at all, but the Fords typically cost several cents more per mile to operate than the GM trucks do ... it isn't a deal breaker, but they do typically cost more ...... now that the government is runnign GM however ..... we've switched back to Ford

Here is a link to a very basic spreadsheet I made in 2000 for doing this if you would like to look it over, you can modify it however you want ...

http://www.spoh.com/~dogmeat/blank cost sheet.xls

here's an example I did on my old 2000 Silverado

http://www.spoh.com/~dogmeat/2000silverado.xls

I'm not trying to bash diesels here at all. I'm really not ... my next truck I'm about %100 positive will be a diesel .... I'm just trying to educate people that just because dieseltub magazine or whatever or whatever printed something in a magazine doesn't necessarily make it true. diesel pickup owners are the reason that Ford didn't go under, so a lot of thanks goes to people who over-bought pickup trucks the last 5 years

I'm just offering some food for thought that maybe you aren't saving any money by buying a truck that costs $7,000 more up front then throwing another $15,000 at it in order to "save money" ....

 

[Snocross 100]

Don't take this to hart....

I'm not saying that diesel dont cost you money to run. Not the case! Nor am I trying to justify the maintenance for one. Unless you work it all the time.

BUT if we are comparing engine to engine, YES diesels are more then 4% efficiency difference! If you put your small block in my P/U (that weights 8,000 pound Crew Cab and lifted with 35's on it) wouldn't come close to the same mileage! Besides that gas has a lower BTU's of heat when compared to Diesel fuel. That = working energy.

Since your small block is in a lighter weight P/U compared to mine, the difference in mileage may not be a big difference. And maintenance cost (on gas) are way less (besides fuel cost, difference in regular to diesel fuel). JMHO

The math would say otherwise.

This is for an ideal air-standard Otto cycle ... meaning, no mechanical losses, losses due to heat transfer, anything ... in a PERFECT world, a spark ignition engine (otto cycle) would approach a MAXIMUM effeciency of ~%67.

Here is the same curve for a Diesel cycle:

So you can see that for a given compression ratio of ~16:1 which is in the neighborhood of what most modern diesels operate, in a PERFECT WORLD the absolute maximum effeciency you could possibly acheive would be approximatley %56 .....

For a spark ignition gasoline motor operating at a compression ratio of 10:1, the effeciency level is is roughly the same ....

The reason diesel-cycle motors are slightly more effecient int he real world is due to the fact that there is no throttleing of the air charge filling the cylinders .... there is no restriction in this way such as on a gas motor. This is also why you can "hop up" your diesel by simply adding more fuel at whatever engine speed you are running at, becuase you take a "full" charge of air in every stroke.

As far as mechanical effeciency goes, that's really it .... there is nothing about diesel motors that makes them inherently more effecient or reliable than a gas motor other than there is no restriction from the throttling process.

I mean really, if diesel motors saved us that much money we'd still be running them for our fleet. I have done some pretty in-depth economic analysis of this and I cannot for the life of me find any condition whatsoever that you are actually saving money in what is the typical lifespan of a modern day pickup truck by buying a diesel UNLESS you are literally towing 10,000-lbs around with you every time you turn the motor on.

Call it what you want to, but the only advantages to buying a diesel truck are power and range. That's it .... given those are two nice things to have, but you are completley fooling yourself if you think you're saving money buying a diesel truck for personal use.

IDK about u guys but both regular and diesel are the same price here and i love my diesel and will never come over to the other side. Plus where u really save ur money is that u can mave ur own fuel for $0.45 a gallon with a diesel.

 

[Ford428CJ]

The math would say otherwise.

This is for an ideal air-standard Otto cycle ... meaning, no mechanical losses, losses due to heat transfer, anything ... in a PERFECT world, a spark ignition engine (otto cycle) would approach a MAXIMUM effeciency of ~%67.

Here is the same curve for a Diesel cycle:

So you can see that for a given compression ratio of ~16:1 which is in the neighborhood of what most modern diesels operate, in a PERFECT WORLD the absolute maximum effeciency you could possibly acheive would be approximatley %56 .....

For a spark ignition gasoline motor operating at a compression ratio of 10:1, the effeciency level is is roughly the same ....

The reason diesel-cycle motors are slightly more effecient int he real world is due to the fact that there is no throttleing of the air charge filling the cylinders .... there is no restriction in this way such as on a gas motor. This is also why you can "hop up" your diesel by simply adding more fuel at whatever engine speed you are running at, becuase you take a "full" charge of air in every stroke.

Give it up on the money!!! I'm not talking money and how much it cost to run!!! IM TALKING EFFICANTCY....ENGINE EFFICANTCY.....Thank you!

Now on NEW Diesels are 16 to 16.5 to 1 on C/R (Fords 6.4 and new 6.7). My 6.0 is 18 to 1. BIG Difference. And the old 6.9 and 7.3 IDI's are about 22 to 1C/R. That you be like your 10 to 1 and upping it to 12 to 1 on your gas (or more).

Also Diesels are (1994 and on) are DI (Direct injected). That helps in making them more efficient and make more power.


[/QUOTE]As far as mechanical effeciency goes, that's really it .... there is nothing about diesel motors that makes them inherently more effecient or reliable than a gas motor other than there is no restriction from the throttling process. [/QUOTE] Not true! Facts are:

Diesel fuel has a higher energy density than gasoline. On average, 1 gallon (3.8 L) of diesel fuel contains approximately 155x106 joules (147,000 BTU), while 1 gallon of gasoline contains 132x106 joules (125,000 BTU). This, combined with the improved efficiency of diesel engines, explains why diesel engines get better mileage than equivalent gasoline engines.

The efficiency of any cycle, be it a gasoline or diesel cycle, is equal to the output divided by the input. The efficiency of the diesel cycle is higher than the gasoline cycle because of higher compression ratio, and because the temperature of combustion in a diesel engine is much higher. Therefore, the heat input in a diesel engine is at a higher average temperature. The higher temperature is outweighed by the increased heat output at that same temperature. A gasoline engine cannot have the same compression ratio as a diesel engine, because fuel and air are mixed before they reach the cylinder, and they would explode before the piston reached the correct firing position, causing the engine to “knock” and not exploit the most efficient use of energy. It is true then that a diesel engine is more cycle efficient.

A Diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol engine (known as a gasoline engine in North America) or gas engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.

Diesel cycle (named after Rudolf Diesel) Diesel engines have the highest thermal efficiency of any internal or external combustion engine, because of their compression ratio. Low-speed Diesel engines' thermal efficiency exceeds 50%+

The efficiency isn't even close!

http://auto.howstuffworks.com/diesel3.htm

http://www.dieselserviceandsupply.com/why_use_diesel.aspx

http://www.ccds.charlotte.nc.us/mcgrail/stu0102/HP10/

http://en.wikipedia.org/wiki/Diesel_engine

 

[Xrider]

. I have done some pretty in-depth economic analysis of this and I cannot for the life of me find any condition whatsoever that you are actually saving money in what is the typical lifespan of a modern day pickup truck by buying a diesel UNLESS you are literally towing 10,000-lbs around with you every time you turn the motor on.

After owning a diesel for the last 10 years I would say the above statement is 100% fact. I haven't done any analyses but just going off imperical thought, I would say this is correct. Now if you like the power of a diesel and don't mind the increased cost and issues like cold start, noise, smell, then by all means go diesel.

 

[Surly1]

I agree ... and there is no reason they shouldn't be able to right now either ...

I'd love to see a decent small block in a Ford truck these days ...

I wonder what will become of the 6.8L V10?

6.8L V-10 is gone, and will not be in the 2011's. Was just looking at the build sheet the other night (contemplating a new one), and the only two motors listed are the 6.7 Diesel and the 6.2 Gasser. The V-10 made the first build sheet for 2011 (in November), the was deleted on the updated sheet in December.

 

[Dogmeat]

Give it up on the money!!! I'm not talking money and how much it cost to run!!! IM TALKING EFFICANTCY....ENGINE EFFICANTCY.....Thank you!

Now on NEW Diesels are 16 to 16.5 to 1 on C/R (Fords 6.4 and new 6.7). My 6.0 is 18 to 1. BIG Difference. And the old 6.9 and 7.3 IDI's are about 22 to 1C/R. That you be like your 10 to 1 and upping it to 12 to 1 on your gas (or more).

Also Diesels are (1994 and on) are DI (Direct injected). That helps in making them more efficient and make more power.


As far as mechanical effeciency goes, that's really it .... there is nothing about diesel motors that makes them inherently more effecient or reliable than a gas motor other than there is no restriction from the throttling process. Not true! Facts are:

Diesel fuel has a higher energy density than gasoline. On average, 1 gallon (3.8 L) of diesel fuel contains approximately 155x106 joules (147,000 BTU), while 1 gallon of gasoline contains 132x106 joules (125,000 BTU). This, combined with the improved efficiency of diesel engines, explains why diesel engines get better mileage than equivalent gasoline engines.

The efficiency of any cycle, be it a gasoline or diesel cycle, is equal to the output divided by the input. The efficiency of the diesel cycle is higher than the gasoline cycle because of higher compression ratio, and because the temperature of combustion in a diesel engine is much higher. Therefore, the heat input in a diesel engine is at a higher average temperature. The higher temperature is outweighed by the increased heat output at that same temperature. A gasoline engine cannot have the same compression ratio as a diesel engine, because fuel and air are mixed before they reach the cylinder, and they would explode before the piston reached the correct firing position, causing the engine to “knock” and not exploit the most efficient use of energy. It is true then that a diesel engine is more cycle efficient.

A Diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol engine (known as a gasoline engine in North America) or gas engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.

Diesel cycle (named after Rudolf Diesel) Diesel engines have the highest thermal efficiency of any internal or external combustion engine, because of their compression ratio. Low-speed Diesel engines' thermal efficiency exceeds 50%+

The efficiency isn't even close!

http://auto.howstuffworks.com/diesel3.htm

http://www.dieselserviceandsupply.com/why_use_diesel.aspx

http://www.ccds.charlotte.nc.us/mcgrail/stu0102/HP10/

http://en.wikipedia.org/wiki/Diesel_engine

I see. So exactly how much more "effecient" is a diesel motor than a gasoline motor? I can't seem to figure this out.

Hold on, I'll answer my own question here:

They aren't that much more effecient, maybe %28 compared to %26 of a modern small block gas motor. It's literally less than a %4 difference in actual real world practice.

So, those were my educated estimates, let's see what one of the links you posted says:

They burn less fuel than a petrol engine performing the same work, due to the engine's higher temperature of combustion and greater expansion ratio.[1] Gasoline engines are typically 25% efficient while Diesel engines can convert over 30% of the fuel energy into mechanical energy.

From: http://en.wikipedia.org/wiki/Diesel_engine

So, in other words "over %30" could mean 30.01, 30.1, 30.375, 31.1 etc .... IE, that article is claiming it's right around %30. I claimed it was right around %28. So, since they're stating it's %25 for a gasoline motor, let's RMS this and see what we're getting here ... looks to me like an average of ~%4.02 better effeciency for the numberst stated above, which may or may not be entirley accurate since there are literally hundreds of different combinations of gasoline and/or diesel motors out there we COULD be talking about here. The only way to compare for sure would be to get fuel consumption curves of each individual motor per brake horsepower made. Then you could really crunch the numbers on that.

But, the moral of the story is still this ... yes, diesel motors ARE more effecient than gasoline motors. No, diesel motors ARE NOT wildley superior in all things fuel effeciency than gasoline motors. Yes, diesel motors ARE better to tow with. No, diesel motors ARE NOT more cost-effective for personal use.

It makes no sense to me whatseover to not take costs into consideration here. You could theoretically have an engine that is %50 more effecient than a gasoline motor, but if it costs you $15,000 per mile to operate it, who cares ....?

If you want the power and range and don't mind paying significantly more for it, get a diesel. If you are willing to put up with the trip taking 20 minutes longer due to slower hill climbs and an extra stop for fuel at a significant cost savings, buy gas.

Power appears to always win out

 

[Ford428CJ]

I see. So exactly how much more "effecient" is a diesel motor than a gasoline motor? I can't seem to figure this out.

Well because of the working energy of the fuel (Diesel has 147,000 BTU and Gas has 125,000 BTU per gallon). Kind of think of it as a food and your a runner! LOL. Diesel has more working energy witch it is measured in BTU's of heat. The more heat, the more working power you can get out of it. So knowing that, you need to run more compression! Cool thing is Diesels are fuel fired (not spark). Super heating the air (using compression to do it) as hot as we can get the air and then adding fuel @ the right time on the power stroke (Not talking Fords LOL). Cant do that with a gas engine, like you can with a Diesel. That would be pre detenation, not good!

Wish I was better with words!LOL
So taking what we know and putting it to use. A Diesel takes around 7000 btu to deliver 1 HP. A gas engine uses over 10,000 BTU to make1 HP. For stationary power a diesel is the most efficient and will generally use 40% less fuel than a gas engine. Stationary power meaning running a generator or a pump @ a set RPM. Just an example for ya. I hoped I answered your Q..... Sorry that my post are sooooo looong. LOL

 

[Dogmeat]

Well because of the working energy of the fuel (Diesel has 147,000 BTU and Gas has 125,000 BTU per gallon). Kind of think of it as a food and your a runner! LOL. Diesel has more working energy witch it is measured in BTU's of heat. The more heat, the more working power you can get out of it. So knowing that, you need to run more compression! Cool thing is Diesels are fuel fired (not spark). Super heating the air (using compression to do it) as hot as we can get the air and then adding fuel @ the right time on the power stroke (Not talking Fords LOL). Cant do that with a gas engine, like you can with a Diesel. That would be pre detenation, not good!

Wish I was better with words!LOL
So taking what we know and putting it to use. A Diesel takes around 7000 btu to deliver 1 HP. A gas engine uses over 10,000 BTU to make1 HP. For stationary power a diesel is the most efficient and will generally use 40% less fuel than a gas engine. Stationary power meaning running a generator or a pump @ a set RPM. Just an example for ya. I hoped I answered your Q..... Sorry that my post are sooooo looong. LOL

You can't make a blanket statement about a motor requiring a certain amount of heat input without relating it to heat input per quantity of fuel burned as well as what engine RPM it is operating at. They don't operate that way ... doesn't matter what fuel you're talking about either, be it gas, diesel, CNG, natural gas, anything.

Are you saying it takes 7,000 btu/s to make 1 horsepower (550 ft-lbs/s)? Or are you saying it took 7,000 btus of total energy in whatever motor at whatever operating RPM and whatever effeciency that particular motor operated at to make 550 ft-lbs of power for one second ....?

Either way that makes no sense to me, because converting that out gives 1 btu as being equal to 778 ft-lbs ... soooo 778 ft-lbs / btu * 7,000 btu = 5446000 ft-lbs .... sooo ... it took 5446000 ft-lbs for the diesel motor to make 550 ft-lbs, giving an effeciency of %0.01 ... that isn't right .... so trying to make sense of that statement, 7,000 btu/s = ~9,900 horsepower ..... so in other words, your combustion process has to make 9,900 horsepower for your diesel to make ...let's just say 360 horsepower .... so you're at a %3.6 effeciency there ...? ... That can't be right either ... I need some help here on this.

I dunno .... I'm just not seeing the outlandish claims of vastley superior thermal effeciency of a diesel motor over a gasoline motor here, regardless of mechanical effeciency or increased heat of combution due to the fuel used ....

I just can't help but think that if they were that much more vastly superiorly effecient it would offset the additional capital and operating costs and there would literally be no such things as gasoline motors whatsoever anymore ... Not that this won't happen eventually due to the fact that you actually DO burn less diesel per mile driven on average .... it's just going to cost the consumer al lot more.....

I dunno, when you think of it in how many bbl/d of oil we'd use as a nation less using diesels, maybe in the long run on a national scale the costs of consumer diesel becoming widespread (read no more gasoline for passenger cars, etc) outweigh the costs of having to import that much more oil ....

I dunno ... like I said, I'm not bashing diesels, I just really fail to see the vastly superior mechanical/thermal/whatever effeciency of these motors on a per-case basis ....