Adding oil to gas tank

[AK IQ Pilot]

So lets take a look at this in a little more detail. At first lets assume that 2 stroke oil does not burn and every bit of oil added to the fuel is displacing a combustible liquid with a noncombustible liquid.

10 gallons of fuel is 1280oz.

Add 13oz of oil to 10 gallons of fuel and you're premixing at about 100:1.

Add 26oz of oil to 10 gallons of fuel and you're premixing at about 50:1

Add 52oz of oil to 10 gallons of fuel and you're premixing at about 25:1

So if you ad 52oz of oil into 10 gallons of fuel you have a 25:1 fuelil ratio. This means about 4% of the mixture is oil and 96% of the mixture is gasoline.

So 26oz of oil into 10 gallons of fuel means you have displaced 2% of the gasoline with 2 stroke oil.

Now lets look at fuel delivery and Main Jet sizes. If you start with a 500 main jet and drop down to a 490 you have reduced the main jet by 2%.

So if 2 stroke oil didn't burn, premixing at 50:1 instead of straight gasoline, would have the same basic effect as dropping 1 main jet size from 500 down to 490. In addition, if your motor was strictly premix and you normally mixed at 50:1 with a 500 main jet you would have to mix at 25:1 to realize a full step down in main jet size. And all of that is assuming 2 stroke oil does not burn.

But we know 2 stroke oil does burn. Source Most modern 2 stroke oils are made from Polybutene feedstock. Polybutene has a flash point of between 215f and 470f. A typically 2 stroke oil has a flash point of about 400f -450f and an auto ignition temp of about 550f - 700f. So when we mix oil into gasoline for premix we are not displacing one flammable fluid for a non flammable fluid we are displacing one flammable fluid for a fluid that is less flammable.

So in summary. Mixing 100:1 premix will have no significant effect on the air fuel ratio. Mixing 25:1 premix very likely has the same effect on the air fuel ratio as dropping 1 jet size at the least and 1.5 jet sizes at the most.

Lots more good info on 2 cycle oil, film strength, piston seizures, etc.

 

[AK IQ Pilot]

Running 20 to 1 oil mix in the tank will decrease the amount of fuel in that mix by 5% because the injector allows only a pre-programmed amount of fluid through at that point just as a jet would (because of diameter) depending on velocity in the venturi. This may be enough to be an issue if you are set perfect for the conditions.
100 to 1 is 1% less fuel. I don't think many are that close to the edge. IMO the added oil to the fuel in the Poo motor helps (maybe in my own mind lol) reduce the possibility of scuffing on the intake side ( seen some pics). The direct spray on the back of the piston MAY wash the thin film of oil off for the short duration of injector opening.
Believe what you want.

The idea of oil in the fuel clogging injector screens or filters is something I have never seen. Other brands inject into the crankcase or upstream of the reeds and can and do run premix only.
I have run inexpensive semi-syn (pretty dirty oil lol) oil for decades in both carb and injector systems at up to 20 to 1 ratios and, like I said, never had an issue with either fuel system.
Believe what you want.

The crankcase of a two stroke is a bit of a collection vessel and there is always a bit of oil sloshing around to give you extra for say 30, 40 secs (picture your start up in a closed garage lol) of lots of oil at WFO.
Lots of oil is good for everything (especially HP) in a two stroke except passing EPA tests and cost of ownership tests. Oil dripping of your crank and staining the cylinder walls is what a builder likes to see when he pulls one apart.
Non pressure fed roller and ball bearings like oil sloshing around. Rings seal better with lots of oil (dynos show more HP with 20 to 1 than 50 to 1 because of ring seal). Piston to cylinder wall contact benefits (less of) from more oil.
Believe what you want.

Some motors today are finally getting the most of your two stroke oil Like the new Cat 600 and the Etec or Ptec or whatever). This is good for those motors because everyone is needing to lower emissions today and oil out the exhaust is bad for the world so they take it away hoping to get through the warranty period before the extra wear shows up lol.
Fingers crossed lol.
Unfortunately the CFI is not one of them. It is still old school let-the-oil-slosh-around and get to where it needs to get to with only crankcase turbulence giving it any direction. The additional lack of fuel in the crankcase (fuel is a lubricant and a cooling agent down there) makes me want more oil.
IMO if there is a new motor from Poo it will address this issue first and power second.
Believe what you want.


History has shown that two-strokes like oil and pay you back with power and life.

So,,, lol, believe what you want.

Very good post geo.

 

[Oregonsledder]

This is good stuff guys. I would like to see EGT data with and without oil added to the gas.

 

[Snodawg]

Anyone remember Dumond Tech Oil. Might even still be around, IDK. I remember running it in the late nineties on my MX race bikes, The company claimed that their oil was "oxygenated" or something, They recommended changing the jetting and even claimed more HP just from running their oil {just like every oil mfg, lol}

 

[Snodawg]

Did a search on Dumond Tech and found this from their website:

Dumonde Tech DTP Synthetic Racing Oil is a neoteric oil. Engineered with technical molecular compounds to provide the highest possible lubrication while maintaining fuel value in racing and recreational vehicles using a premix oil system. Dumonde Tech DTP is most definitely the “state of the art lubrication” which pushes the technology envelope further than any other oil in the world! Benefits: Increases Horsepower by technology Quick, Clean throttle response No plug fouling No power value sticking and build up Mixes with all fuels Exceptionally clean burn which reduces pollution. Mix Ratios: 32:1 to 50:1 Average usage ratio 40:1. Enriching of carburation is usually required. Availability: Pints, 1/2 Gallons and Gallons - See more at: http://www.dumondetech.com/dumonde/motorsports/#sthash.S8JXWsGl.dpuf

 

[RoffRider]

i would think that you would start running into fouled plugs and very hard starting along with running problems and diesel like throttle response before you burn down a motor on a stock sled from mixing gas

 

[RoffRider]

Did a search on Dumond Tech and found this from their website:

Dumonde Tech DTP Synthetic Racing Oil is a neoteric oil. Engineered with technical molecular compounds to provide the highest possible lubrication while maintaining fuel value in racing and recreational vehicles using a premix oil system. Dumonde Tech DTP is most definitely the “state of the art lubrication” which pushes the technology envelope further than any other oil in the world! Benefits: Increases Horsepower by technology Quick, Clean throttle response No plug fouling No power value sticking and build up Mixes with all fuels Exceptionally clean burn which reduces pollution. Mix Ratios: 32:1 to 50:1 Average usage ratio 40:1. Enriching of carburation is usually required. Availability: Pints, 1/2 Gallons and Gallons - See more at: http://www.dumondetech.com/dumonde/motorsports/#sthash.S8JXWsGl.dpuf

lubrication comes at a price...

castor based oils would work great, but even in the days of no VES they would cause lots and lots of carbon build up, so the manufactures added detergents and "cleaners" to oil, which made lubrication worst but didnt gum up an engine

 

[Jaynelson]

I put a couple/few glugs (very scientific.......not) in each tank, warm the basterd all the way up, take it easy the first few miles, then do as I please. Hasn't blow'd up yet. So either I'm a genius, or the thing isn't THAT finicky unless you're a complete window licker.

Do I think this is going to save it from potential issues such as piston slap/skirt failure or improper internal tolerances should they exist? Nope. I just like the idea of a little extra oil in a 2-stroke that sees a lot of WOT, ya'know?

 

[RKT]

IMO

Adding oil (at least 150:1) in every tank of fuel will help with ring seal and , more importantly, lubrication on the cylinder walls.. If you do not do it, then you will not suffer enginefailure it is just one of those "wise things" to do type deals..

It will not lean out the mixture to the point of failure

Adding oil will not help with any tolerance or piston issues..This is a piston problem and can easily be resolved with a better piston...

 

[5STAR]

Ok I might be wrong here but if you add a little oil to your tank, you are getting some of that oil into the bottom end as well. As the 2 stroke engine cycles the fuel is drawn into the crank case and then makes its way up through the transfer ports to the top of the piston to be ignited. I would agree that the end bearings would get a little less of this extra oil as compared to the main crank bearing! Just add a little to the tank at a 100:1 and ride the fricken thing!

 

[DLynn]

I will agree with Kelsey on this one. Reasonable amounts of oil are one thing. Several years ago I was running a Polaris 800 carbed motor with pyrometers. Out of the blue on a long pull at WOT I got a Flashing EGT Warning. Backed out and things settled down. WOT, and temps went right up again. After tearing into the problem I found a broken oil pump cable. The fail safe was max oil output on a open oil pump. So with the extra oil being added via the crank case and the throttle bodies it leaned out the fuel mixture to the point it went dead lean.
So I would say if you decrease fuel and keep the air the same you will get higher EGT. At what point will it burn the motor down?? Your guess is as good as mine. On a injected sled the fuel oil path is different however the combustion chamber it still were the EGT is being created. If someone wants to let me use their sled I will figure it out and let you all know.
That's my 2 cents.

 

[AK IQ Pilot]

IMO

Adding oil (at least 150:1) in every tank of fuel will help with ring seal and , more importantly, lubrication on the cylinder walls.. If you do not do it, then you will not suffer enginefailure it is just one of those "wise things" to do type deals..

It will not lean out the mixture to the point of failure

Adding oil will not help with any tolerance or piston issues..This is a piston problem and can easily be resolved with a better piston...

I can agree with all of that for sure but a couple of questions.

1. If ring seal is improved by adding extra oil why does it matter if you add 13 oz to your fuel or increase your oil pump output by 13 ozs. All the oil makes it to the combustion chamber either way. With regards to ring seal, how is adding the oil to your fuel more beneficial than just increasing pump output?

2. If increased lubrication to the cylinder walls is the benefit how is it more beneficial to add the extra oil only to the top half of the motor and not to the entire motor ie. the piston skirts and cylinder skirts. When the extra oil is injected it coats the piston skirts and cylinder skirts before it makes its way to the top of the motor where it again coats the pistons and cylinders. With regards to piston and cylinder lubrication I don't understand how adding oil to the fuel would have more benefit than just increasing oil pump output.

IMO it's quite clear that increasing oil pump output has far more benefit than just adding oil to your fuel and lubricating the top end. The oil film is providing additional lubrication throughout the entire motor and not just the top half of the motor.


As geo pointed out. The one significant benefit to adding oil to the fuel is the injectors will have less of a tendency to wash the lubrication from the piston around the boost port area. Here is one point where adding oil to the fuel is for sure a benefit. Intake side scuffing could be reduced by adding oil to the fuel but I do not see any other lubrication benefit to adding oil just to the fuel and not through the oil pump.

Discuss.

 

[AK IQ Pilot]

I will agree with Kelsey on this one. Reasonable amounts of oil are one thing. Several years ago I was running a Polaris 800 carbed motor with pyrometers. Out of the blue on a long pull at WOT I got a Flashing EGT Warning. Backed out and things settled down. WOT, and temps went right up again. After tearing into the problem I found a broken oil pump cable. The fail safe was max oil output on a open oil pump. So with the extra oil being added via the crank case and the throttle bodies it leaned out the fuel mixture to the point it went dead lean.
So I would say if you decrease fuel and keep the air the same you will get higher EGT. At what point will it burn the motor down?? Your guess is as good as mine. On a injected sled the fuel oil path is different however the combustion chamber it still were the EGT is being created. If someone wants to let me use their sled I will figure it out and let you all know.
That's my 2 cents.

So let me get this straight. You saw a lean air/fuel mixture when your oil pump cable broke and your oil pump went to max output on a carbed motor.

Can you explain how the air/fuel mixture was altered with only an increase in oil pump output. This is very puzzling to me.

 

[AK IQ Pilot]

Ok I might be wrong here but if you add a little oil to your tank, you are getting some of that oil into the bottom end as well. As the 2 stroke engine cycles the fuel is drawn into the crank case and then makes its way up through the transfer ports to the top of the piston to be ignited. I would agree that the end bearings would get a little less of this extra oil as compared to the main crank bearing! Just add a little to the tank at a 100:1 and ride the fricken thing!

Not on a CFI-2 motor. We are discussing a CFI-2 in this thread.

 

[RoffRider]

I can agree with all of that for sure but a couple of questions.

1. If ring seal is improved by adding extra oil why does it matter if you add 13 oz to your fuel or increase your oil pump output by 13 ozs. All the oil makes it to the combustion chamber either way. With regards to ring seal, how is adding the oil to your fuel more beneficial than just increasing pump output?

2. If increased lubrication to the cylinder walls is the benefit how is it more beneficial to add the extra oil only to the top half of the motor and not to the entire motor ie. the piston skirts and cylinder skirts. When the extra oil is injected it coats the piston skirts and cylinder skirts before it makes its way to the top of the motor where it again coats the pistons and cylinders. With regards to piston and cylinder lubrication I don't understand how adding oil to the fuel would have more benefit than just increasing oil pump output.

IMO it's quite clear that increasing oil pump output has far more benefit than just adding oil to your fuel and lubricating the top end. The oil film is providing additional lubrication throughout the entire motor and not just the top half of the motor.


As geo pointed out. The one significant benefit to adding oil to the fuel is the injectors will have less of a tendency to wash the lubrication from the piston around the boost port area. Here is one point where adding oil to the fuel is for sure a benefit. Intake side scuffing could be reduced by adding oil to the fuel but I do not see any other lubrication benefit to adding oil just to the fuel and not through the oil pump.

Discuss.

the degreasing traits of gasoline are reduced when you mix gas

 

[Quicksand]

I Dont think kelsey was saying not to play with the oil pump, just that adding oil to the tank is also benificial

 

[DLynn]

So let me get this straight. You saw a lean air/fuel mixture when your oil pump cable broke and your oil pump went to max output on a carbed motor.

Can you explain how the air/fuel mixture was altered with only an increase in oil pump output. This is very puzzling to me.

When I stated max oil pump output I should have said "Way more oil than would normally be put out by the pump when the cable is connected correctly". So with the increase in oil into the fuel /air mix the amount of fuel is decreased and replaced by oil. Oil doesn't burn at the same rate as fuel so with less fuel to cool the combustion cycle the mixture burn temperature increases causing a "Lean" condition which causes high EGT. There's only so much oil, fuel and air ingested each cycle. If we change the ratio's then we affect the lubrication, burn rate and temperature of the cycle. That's a long winded explanation....as I see it. I am sure there are some engineers on her that could explain it much better.

 

[AK IQ Pilot]

When I stated max oil pump output I should have said "Way more oil than would normally be put out by the pump when the cable is connected correctly". So with the increase in oil into the fuel /air mix the amount of fuel is decreased and replaced by oil. Oil doesn't burn at the same rate as fuel so with less fuel to cool the combustion cycle the mixture burn temperature increases causing a "Lean" condition which causes high EGT. There's only so much oil, fuel and air ingested each cycle. If we change the ratio's then we affect the lubrication, burn rate and temperature of the cycle. That's a long winded explanation....as I see it. I am sure there are some engineers on her that could explain it much better.

How was the fuel passing through the carb reduced and replaced by the oil when the oil pump went to max?

Oil check valves in carbs are placed down stream of the venturi and main jet/jet needle port. Pumping more oil into the check valve has no effect on the airflow through the venturi. If airflow through the venturi is not affected then neither is the fuel flow because fuel flow through the Main Jet and Jet Needle are directly proportional to the throttle position and the air moving through the venturi.

I don't see how adding extra oil with an oil pump could have any effect on the air/fuel ratio. The two systems are mutually exclusive, changing one has no affect on the other.

 

[sledneck_03]

I can agree with all of that for sure but a couple of questions.

1. If ring seal is improved by adding extra oil why does it matter if you add 13 oz to your fuel or increase your oil pump output by 13 ozs. All the oil makes it to the combustion chamber either way. With regards to ring seal, how is adding the oil to your fuel more beneficial than just increasing pump output?

2. If increased lubrication to the cylinder walls is the benefit how is it more beneficial to add the extra oil only to the top half of the motor and not to the entire motor ie. the piston skirts and cylinder skirts. When the extra oil is injected it coats the piston skirts and cylinder skirts before it makes its way to the top of the motor where it again coats the pistons and cylinders. With regards to piston and cylinder lubrication I don't understand how adding oil to the fuel would have more benefit than just increasing oil pump output.

IMO it's quite clear that increasing oil pump output has far more benefit than just adding oil to your fuel and lubricating the top end. The oil film is providing additional lubrication throughout the entire motor and not just the top half of the motor.


As geo pointed out. The one significant benefit to adding oil to the fuel is the injectors will have less of a tendency to wash the lubrication from the piston around the boost port area. Here is one point where adding oil to the fuel is for sure a benefit. Intake side scuffing could be reduced by adding oil to the fuel but I do not see any other lubrication benefit to adding oil just to the fuel and not through the oil pump.

Discuss.

magic numbers still 3 turns in right???

 

[AK IQ Pilot]

magic numbers still 3 turns in right???

Yes, that's what I do. Should average about a 40:1 fuelil ratio with that setting. Of course this is dependent on how far you mash the throttle on every ride.