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Adding oil to gas tank

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Oregonsledder

Well-known member
Jan 27, 2009
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Bend Oregon
I know this has been discussed a bit, but I think the fact that there seems to be two very different views on this is interesting. Let me start the debate by raising a few questions.
First many say adding oil to the gas leans out the burn, why do you think that? Why would sled manufactures add oil to new sleds gas tanks for the initial break in period. If the oil causes a lean condition, would it be smart for a manufacturer to suggest this on a new tight engine?

Second, most two stroke engines from the very beginning have had oil in the gas, why has that worked so well for so many years? The desired gas to oil ratio is approximately the same whether the engine is injected with oil or if it’s mixed in the gas. And yes I understand that the oil injection is not direct injection, but for the sake of this discussion it shouldn’t matter.

There is also the issue of oiling the bottom end with injection systems, but that’s not what I want this thread to discuss.

What are your thoughts on whether oil added to gas leans out the burn, and if so why is that?
 

89sandman

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Oct 16, 2004
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southern oregon
my pro would go from about 30:1 on deep days to about 55:1 on hardpack days. oil injection sucks. on hardpack days i would add 4 ounces of oil to the tank just for insurance. lets say you have 10 gallons in the tank and add 4 ounces of oil thats a mix ratio of 320:1 in the tank. not enough of a difference to cause a lean condition...
 
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waxer

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Nov 2, 2012
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This could be a very good topic just hope it can stay on track! Technically more oil is a leaner fuel/air mixture,sure, but as Sandman said 4 or even 8 oz to the tank shouldn't cause a lean issue.Extra oil ( lubrication) ,not too much, is a good thing:face-icon-small-hap I don't think too many riders do it but checking plugs & pistons, done correctly, is the real way to know what your burn is, and as you know that doesn't mean checking at an idle.
With carbs we could adjust for this on the track,some efi machines had a adjustable fuel regulator too, now if we have an issue we have fuel controllers but not too many are going this route with "stock" engines but some do. I spoke with SLP and they don't even have a map for a stocker on the 800 POO.
Lastly shouldn't EFI adjust fuel/air for a little more oil????MAYBE MAYBE Not!
 

xcmark

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Dec 2, 2007
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Mass-hole
the quest for using less oil is required by EPA , I think. by passing rules like they have a Yellowstone the OEM try to break new ground every year on getting the MAX out of there product and the min to the in terms of foot print. Husqvarna has the same problem with running 50:1 in there XP line of high end saws , they want more oil then is suggested in the owners manual but can live (maybe not as long) with a 50:1 ratio of good oils. Its been proven many times that more oil will produce more power but Big Brother wants less so WHO is looseing out..... That would be you and me! WHo asked for MBTE to be put in the gas ......EPA , that was a good idea wasn't it!


Rant over
 
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550iq

Well-known member
Oct 7, 2008
558
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Anchorage, Alaska
Break-in oil was added to the fuel for my 013 800 as requested by the dealer and such. What concerns me more is the quality of fuel we get anymore. Banging off the det-sensor time and again even with the low octane setting on is disconcerting. Adding oil to the fuel tank didn't help this situation at all. 550iq
 
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waxer

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Nov 2, 2012
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Adding oil to the fuel tank didn't help this situation at all. 550iq[/QUOTE]

No and it won't:face-icon-small-hap
 
S

sledneck_03

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Jan 3, 2009
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Saskatoon, SK
you could argue that your suppose to break your motor in that first tank, varying throttle not holding it open for long stretches.... but you can also lean your motor out mid throttle right?
 
6
Jul 11, 2001
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Waconia, MN
This could be a very good topic just hope it can stay on track! Technically more oil is a leaner fuel/air mixture,sure, but as Sandman said 4 or even 8 oz to the tank shouldn't cause a lean issue.Extra oil ( lubrication) ,not too much, is a good thing:face-icon-small-hap I don't think too many riders do it but checking plugs & pistons, done correctly, is the real way to know what your burn is, and as you know that doesn't mean checking at an idle.
With carbs we could adjust for this on the track,some efi machines had a adjustable fuel regulator too, now if we have an issue we have fuel controllers but not too many are going this route with "stock" engines but some do. I spoke with SLP and they don't even have a map for a stocker on the 800 POO.
Lastly shouldn't EFI adjust fuel/air for a little more oil????MAYBE MAYBE Not!

Should the ECU adjust for fuel/air ratio? Yes it should, but most OEM 2T (2-stroke) EFI systems are an open loop design this means that there is not o2 sensor to provide the feedback nessary to adjust the air/fuel ratio. So the Manufactures program the systems in the lab with build the maps and write them to the ECU. In this scenario the ECU can only adjust the fuel delivery based on the parameters that it is given in the internal maps.

In a Closed loop system the ECU would have an o2 sensor in the exhaust that would provide the feedback loop that can give the ECU extra data about the air/fuel ratio and the ECU would have instructions programed into it to add fuel or take it away based on the desired air/fuel ratio.

Why do the manufactures not change to a Closed Loop system? My guess is it is cost and maintenance. o2 sensors will have a shortened life span in a 2T exhaust environment due to the oil can foul the o2 sensor much faster. Personally I think for the cost of an o2 sensor now at under 100.00 this could be an annual maintenance item that is as easy to change as a spark plug.

Dyno-jet Research does have an add-on to the new PCV called autotune that essentially converts the EFI system to a closed loop system. There is intellegence built in to it that you can give it a desired air/Fuel ratio and it will make adjustments to the program in the PCV to achieve the air/fuel parameter you give it. The only problem is it does not come cheap. With the questionable fuel that we can sometimes get out there this technology would be a good addition to save the engine from a burn down on top of the tech that is already built into the current systems.
 
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Rev Kev

Well-known member
Nov 27, 2007
377
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Lapeer Michigan
The fuel ~vs~ oil and lean debate is basically this, lets say the injector flows 5mm of fuel pre firing stroke, now displace some of that fuel with oil, lets say for sake of arguement, 1mm, now you are only flowing 4mm of fuel, and 1mm of oil, basically you are now introducing less fuel with the same amount of air, this equates a lean condition, enough to make a real world difference? I doubt it. As far as adding extra lubrication to the bottom end, it will not, as fuel is injected into the transfer port, as it enters the combustion chamber, so no added benefit to the bottom end, but yes to the piston and upper rings. Turning up the oil pump is the only real way to add lube to the bottom end. My $0.2
 
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waxer

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Nov 2, 2012
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Should the ECU adjust for fuel/air ratio? Yes it should, but most OEM 2T (2-stroke) EFI systems are an open loop design this means that there is not o2 sensor to provide the feedback nessary to adjust the air/fuel ratio. So the Manufactures program the systems in the lab with build the maps and write them to the ECU. In this scenario the ECU can only adjust the fuel delivery based on the parameters that it is given in the internal maps.

In a Closed loop system the ECU would have an o2 sensor in the exhaust that would provide the feedback loop that can give the ECU extra data about the air/fuel ratio and the ECU would have instructions programed into it to add fuel or take it away based on the desired air/fuel ratio.

Why do the manufactures not change to a Closed Loop system? My guess is it is cost and maintenance. o2 sensors will have a shortened life span in a 2T exhaust environment due to the oil can foul the o2 sensor much faster. Personally I think for the cost of an o2 sensor now at under 100.00 this could be an annual maintenance item that is as easy to change as a spark plug.

Dyno-jet Research does have an add-on to the new PCV called autotune that essentially converts the EFI system to a closed loop system. There is intellegence built in to it that you can give it a desired air/Fuel ratio and it will make adjustments to the program in the PCV to achieve the air/fuel parameter you give it. The only problem is it does not come cheap. With the questionable fuel that we can sometimes get out there this technology would be a good addition to save the engine from a burn down on top of the tech that is already built into the current systems.
This is why I said if we have an issue we have fuel controllers:face-icon-small-hap
 
R

RETRO ASSAULT

Banned
Oct 17, 2013
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Firestone Co, North Denver
A person can NOT burn a sled down by adding too much oil to the gas tank. It won't happen. Just can't happen. I'm not saying the fuel to air ratio does not go up but the oil to air for sure goes down. I can't believe someone would think they could burn down an engine by adding more oil. As for not messing with the oil pump setting. The oil pump has a barrel valve in it and if you turn it too far you'll start closing off the oil port. So you will supply your engine with more oil at 1/2 and 3/4 throttle but at full throttle you will have less If you turn up the oil pump too far.
Not my .02, facts.
One last thing, the oil pumps that are found on at least Polaris and Arctic Cat snowmobiles do not supply a constant flow of oil. they pump like a pneumatic fuel pump. gulps of oil, not a constant flow like you'd see in a car engine. So adding oil to the gas tank bridges the gap between gulps.
I run stock oil injection settings and run 100:1 pre mix in the gas tank. I started doing this 10 years ago and have not lost a crank or scored a piston in the last ten years. And a added benny of oil in the gas tank, it lubes injectors, the fuel pump, fuel line O-rings and helps keep the crap fuel from eating at fuel system.
I don't always hold my snowmobile throttle wide open but when I do, I would like the oil pump port to be wide open, Not closed off because I adjusted it too far.
 
Last edited:
C
Sep 11, 2011
22
3
3
For the guys adding oil to the gas - are you pre-mixing in a container and adding that to the tank? Or just dumping oil from the jug?
 

likkerpig

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Nov 28, 2007
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What he said. If you have an air bubble in your oil lines, you can grab the pump arm at idle and force the pm to run wfo. The pump doesn't run constantly, it goes in "spurts".
 

freak485

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Feb 4, 2011
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Billings, MT
What he said. If you have an air bubble in your oil lines, you can grab the pump arm at idle and force the pm to run wfo. The pump doesn't run constantly, it goes in "spurts".


Has anyone tested this to see what the ideal amount of turns to turn the oil pump is? or what is considered to far?
 
R

RETRO ASSAULT

Banned
Oct 17, 2013
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Firestone Co, North Denver
I have never done a flow test but it might be that if you set any pump past where it was designed to be set at, you might be using less oil at WFO.
You will use more oil per tank of gas because you don't drive wide open all day and the pump is wide open at 3/4 throttle.
So if im right, adjusting your oil pump past the correct set point would will always lean the oil out at wide open throttle.
Now, im not say im right but I just might be.
 
A

AK IQ Pilot

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Dec 29, 2007
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my pro would go from about 30:1 on deep days to about 55:1 on hardpack days. oil injection sucks. on hardpack days i would add 4 ounces of oil to the tank just for insurance. lets say you have 10 gallons in the tank and add 4 ounces of oil thats a mix ratio of 320:1 in the tank. not enough of a difference to cause a lean condition...

As your experience clearly demonstrates the oil pump flow and in turn oil consumption is directly proportional to the throttle position. Throttle position has a much greater effect on oil pump flow than engine RPM.

If you tied the oil pump lever wide open and let the motor idle your oil tank would be empty in under 30 minutes and you wouldn't have burned even half a gallon of fuel.

Conversely, if you putz around at 1/4-1/2 throttle for long periods of time you will use hardly any oil and you will see well in excess of 100:1 fuel oil ratio even though you may see 7000 RPM periodically.

Oil mixed into the fuel of a modern 2 stroke does nothing for the crank/crank bearings/rod bearings and almost nothing for the piston and cylinders.

You would have to dump gallons of oil into a tank of fuel to see any noticeable differences in the fuel/air ratio. So oil added to the fuel has very little chance of leaning out the motor.
 
R

RETRO ASSAULT

Banned
Oct 17, 2013
73
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Firestone Co, North Denver
(This comment below is only right if you have a direct injection engine like a skidoo, but we ride Polaris here. The injector sprays right into the case so adding oil on a Polaris works)

Oil mixed into the fuel of a modern 2 stroke does nothing for the crank/crank bearings/rod bearings and almost nothing for the piston and cylinders.
 
Last edited:
R
Sep 8, 2013
232
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28
Interior Alaska
lots of manufactuers make the sled rich during break in, and theres the "myth" that timing is retarded too(i dont know about that) during break in

adding oil the the gas will help with piston and cylinder lubrication, but more importantly it will help with getting rid of that de-greasing trait gasoline has and help stop washing oil off the piston as much

and yeah adding oil will lean the mixture, but not enough to run into lean problems with stock map...but if you have an egt gauge and pcv i would check the egt temps if im mixing the gas with a considerable amount of oil

turning up your pump to 55:1 at WOT and mixing your gas as much as 1 oz per gallon would get a good deal for your sled and will be happy
 
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waxer

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Nov 2, 2012
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For the guys adding oil to the gas - are you pre-mixing in a container and adding that to the tank? Or just dumping oil from the jug?

Always mix it in a container first, usually in my 5 gal jug :face-icon-small-hap
 
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