Pump or AV gas?

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9/22/2015 6:33 PM

Hey everyone, so I just bought a 2014 Ktm 250sx. I've been doing a lot of research on here and other places on the Internet on whether to run pump, AV, or race gas. I thought I had made my mind up to run AV gas until I went to my local shop today. They said to just run pump gas. So what do you guys think? Also I've been running 32:1 ratio in my yz125. Would that be fine in my new bike?
Thanks!

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9/22/2015 7:01 PM

92 or 93 oct pump gas should be fine. 32:1 or 40:1 will work great on that bike.

Paw Paw

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9/22/2015 10:43 PM

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

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9/23/2015 4:33 AM

I have a 15 250sx and have been running 93 pump at 45:1 (motorex). Don't seem to have any issues. Just makes sure the jetting is good on it. The bike is known to come from the factory jetted very poorly. There's plenty of threads on here of the preferred set up.

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9/23/2015 4:44 AM

Awesome! Thanks for the feed back.

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9/23/2015 8:44 AM

JH911 wrote:

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

Ridiculous argument....and that's I am going to say.

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9/23/2015 9:18 AM

JH911 wrote:

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

slackinoff wrote:

Ridiculous argument....and that's I am going to say.

I will agree that I do not find the car oil point valid. I do not have any experience with av fuel to comment on its usefulness. As far as automotive oil in a bike, you are fine. If it was such an issue then why would recluse recommend rotella?

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9/23/2015 10:20 AM

JH911 wrote:

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

slackinoff wrote:

Ridiculous argument....and that's I am going to say.

It is largely a ridiculous argument.

The basic contention is that AV gas isn't designed for high rpms. Neither is pump piss. A justification can obviously be made in favor of race fuels for this (and other points), but the swill from the pump is designed for anything but performance.

If the engine can't utilize 100+ there's no point in wasting $. Not entirely true.
-Unlike pump piss, Av gas has far less enviro-nazi additives and burns far cleaner. This makes jetting easier and more consistent. The lack of so many ridiculous blends assists in that too.
-While an engine may not require 100 octane, if it's on the edge of detonation with PP (pump piss), then the additional octane will provide a safety buffer, particularly if there's a higher load (mud, sand, etc), or as the engine wears in.
-Without the additives, there is a more complete burn, at least from the standpoint of not leaving drool in the silencer and carbon on the piston and power valves.

In my personal experience, every bike I've run 100LL in has either run better (RM85's, YZ85's, YZ125, KX125, CR250, YZ250, CRF250R, CRF450R, and more), or has had no noticeable effect (XR50, TTR90, TTR125, WR250F, Briggs and Stratton).

To JH911's credit, his statement of "Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better." is completely correct. So while my TTR125 and lawn mower might smell better with AV gas, they don't perform better. Actually because the compression ratio is so low on them, 87 octane will likely produce more power than 100 octane non-oxygenated fuel will.

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9/23/2015 11:41 AM

JH911 wrote:

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

I basically agree with Matt Fisher's statement above, but wanted to add one thing:

I have heard statements about AV gas most of my life.
What I have never heard from anyone is a scientifically informative explanation of how the chemical composition of AV gas is significantly different from automotive fuel including how and why those differences will cause negative effects on the performance or longevity of a 2 stroke racing motorcycle engine.


AV gas is superior to pump fuel in real world use in a 2 stroke motocross bike. It is more consistent, easier to jet and less prone to detonation. As for which fuel makes more horsepower, who cares. Run the fuel that makes the bike more reliable and consistent.

True racing gasoline is a huge improvement over both of the other options in both consistency and horsepower.



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9/23/2015 8:08 PM

Avgas is essentially ethanol free premium pump gas with 2 grams of lead added.

The avgas critics simply don't know what they are talking about.

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9/24/2015 8:31 AM

I have run 91 pump w/o ethanol in my 2014 250SX it' s whole life with no problems whatsoever.

However, I am going to switch to AV gas or straight race gas soon, for the simple fact that it is consistent year round. I'm planning on riding indoors this winter, and I don't want to run winter blend. Not to mention, I don't ride a huge amount maybe once a week, and race gas smells amazing.

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9/24/2015 8:43 AM

I've been using a 50/50 mix of pump 91 and 100LL for a while now and have been really happy with it. The car oil argument above is ridiculous since in two strokes the only place motor oil is going is through the trans and clutch. The only reason I don't run regular car oil is because of the wet clutch, but at the same time I ran it for years beforehand so I probably never even needed to switch. I like the 100LL because it keeps the detonation down in my yz250 and cr125, before I tried it I was getting quite a bit in the 125 and it was a little unsettling. I say give it a try and see what you think, I don't think you will be disappointed, especially with how economical it is to run when you mix it with pump gas.

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Make Hillclimb Great Again

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9/24/2015 2:52 PM

Who said this was an argument?? I laid out a few facts in the most simple explanation possible just as a reference, but since people on vital seem to like to argue and discredit anyone who doesn't see things their way. Let's start with car oil facts. Very few car oils are MA rated. MA rated means suitable for wet clutch/transmission use. Rotella T is one exception as it is MA rated and a mineral base oil. Rotella also has semi and full synthetics that are not MA rated. Most car oils are MB rated, meaning suitable only as an engine oil, which is fine if you have a Honda or certain KTM with a twin sump engine. Fact still remains car oils are not engineered to turn the RPM's demanded of todays motocross bikes. Nor the internal temperatures that can be generated in a motocross bike. Oil oxidization, thermal break down, and shear stability of the oil is now a problem. "The car oil argument above is ridiculous since in two strokes the only place motor oil is going is through the trans and clutch." Maybe you should again consider that car oil is again not rated for clutch/transmission use. It is not engineered to withstand the shearing that it incurs while running through the clutch and transmission, which in short means it will break down quickly and fail to properly lubricate. The other issue being car oils use additive packages/friction modifiers that are designed to go where heat and friction is. Guess where that is in a 2-stroke? The clutch. Since clutch friction plates are fiber material it's pretty easy for those additives/friction modifiers to impregnate those plates and glaze the drive plates causing the clutch to slip. Will it happen right away?? Next couple rides?? Months?? Ever?? Dunno. Depends on the oil and the frequency your changing it and or abusing your clutch. I'm not even saying it will happen. I've seen it happen in one ride with a particular Lucas oil and I've seen it happen over time with a kid who was using chevron oil. I'm stating the fact that oil companies produce specific oils for specific applications and demands. Not just so they can take your money and rip you off. There is a reason those oils cost more. Myself personally I use oils designed and engineered for my bikes and my riders/customers bikes. Serious racers, Race Teams, Engine Tuners/Builders don't use car oils. What I find ridiculous is how many of you are willing to put just about anything in your bikes to save a couple $$$. Then berate others for expressing a difference of opinion or presenting facts. If your going to state something is ridiculous then you should probably back it up with some facts. Not just post "Ridiculous argument....and that's I am going to say."

Moving on to AV Gas. I threw out something I was told by an old aircraft pilot and a current commercial airline pilot, both expressing opinions why they wouldn't use AV gas instead, just using a quality race fuel. I guess like myself they believe in using things that were designed and engineered for your specific application. I have also been told by a former aircraft mechanic aside from burn speed; AV gas was designed for high altitude and low compression engines. Which I found interesting being as it is not oxygenated. If your going to cut it then what's the difference?? A couple $$? Run some race gas. AV gas has a ton of great properties. Consistent, stable, won't go bad for a long time, contains lead (although I have seen plugs lead foul). However, once again the point was to use what is engineered and designed for your application. As far as AV gas vs pump specifically, I guess it depends on where you live and where you get your gas. I guess I take for granted we have a local bulk plant/station that for over 40 years has sold nothing but quality ethanol free gas that is consistent and blends don't change with seasons because they're not a franchise station that has that dictated for them. They also sell race gas at the pump that's not much more than AV. I prefer Renegade or VP myself, but again to each their own.

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9/24/2015 10:58 PM

JH911 wrote:

Who said this was an argument?? I laid out a few facts in the most simple explanation possible just as a reference, but since people on vital seem to like to argue and discredit anyone who doesn't see things their way. Let's start with car oil facts. Very few car oils are MA rated. MA rated means suitable for wet clutch/transmission use. Rotella T is one exception as it is MA rated and a mineral base oil. Rotella also has semi and full synthetics that are not MA rated. Most car oils are MB rated, meaning suitable only as an engine oil, which is fine if you have a Honda or certain KTM with a twin sump engine. Fact still remains car oils are not engineered to turn the RPM's demanded of todays motocross bikes. Nor the internal temperatures that can be generated in a motocross bike. Oil oxidization, thermal break down, and shear stability of the oil is now a problem. "The car oil argument above is ridiculous since in two strokes the only place motor oil is going is through the trans and clutch." Maybe you should again consider that car oil is again not rated for clutch/transmission use. It is not engineered to withstand the shearing that it incurs while running through the clutch and transmission, which in short means it will break down quickly and fail to properly lubricate. The other issue being car oils use additive packages/friction modifiers that are designed to go where heat and friction is. Guess where that is in a 2-stroke? The clutch. Since clutch friction plates are fiber material it's pretty easy for those additives/friction modifiers to impregnate those plates and glaze the drive plates causing the clutch to slip. Will it happen right away?? Next couple rides?? Months?? Ever?? Dunno. Depends on the oil and the frequency your changing it and or abusing your clutch. I'm not even saying it will happen. I've seen it happen in one ride with a particular Lucas oil and I've seen it happen over time with a kid who was using chevron oil. I'm stating the fact that oil companies produce specific oils for specific applications and demands. Not just so they can take your money and rip you off. There is a reason those oils cost more. Myself personally I use oils designed and engineered for my bikes and my riders/customers bikes. Serious racers, Race Teams, Engine Tuners/Builders don't use car oils. What I find ridiculous is how many of you are willing to put just about anything in your bikes to save a couple $$$. Then berate others for expressing a difference of opinion or presenting facts. If your going to state something is ridiculous then you should probably back it up with some facts. Not just post "Ridiculous argument....and that's I am going to say."

Moving on to AV Gas. I threw out something I was told by an old aircraft pilot and a current commercial airline pilot, both expressing opinions why they wouldn't use AV gas instead, just using a quality race fuel. I guess like myself they believe in using things that were designed and engineered for your specific application. I have also been told by a former aircraft mechanic aside from burn speed; AV gas was designed for high altitude and low compression engines. Which I found interesting being as it is not oxygenated. If your going to cut it then what's the difference?? A couple $$? Run some race gas. AV gas has a ton of great properties. Consistent, stable, won't go bad for a long time, contains lead (although I have seen plugs lead foul). However, once again the point was to use what is engineered and designed for your application. As far as AV gas vs pump specifically, I guess it depends on where you live and where you get your gas. I guess I take for granted we have a local bulk plant/station that for over 40 years has sold nothing but quality ethanol free gas that is consistent and blends don't change with seasons because they're not a franchise station that has that dictated for them. They also sell race gas at the pump that's not much more than AV. I prefer Renegade or VP myself, but again to each their own.

I don't think anyone is trying to discredit you, but you have to realize there are way too many people using 100LL successfully for many of the old arguements against it to be true. To be fair though, I run it through a bone stock motor, and am not looking for performance gains, only to keep detonation down. I understand that fuels are engineered for different applications, but not everything in theory translates over to practice, especially enough to make a noticeable difference to a rider. There are a few reasons I run AV over race gas:

1. Price. I just picked some up today for 4.50 a gallon, that's a pretty economical fuel for guys like me on a budget.

2. Availability. I pass by a small airport very often so it is easier for me to get than race gas, which I would have to get through a shop or dealer that i don't frequent as often.

As for the car oil, I already said I no longer run it due to the wet clutch found in all our bikes. I used to run a Castrol motorcycle oil but switched to Rotella after reading around online. For those who like to stretch their oil changes out then they might notice some issues with car oil, but for me I never had a problem since I changed it so frequently. I probably wouldn't recomend running car oil to anyone, but I honestly never had any problems for all the years I used it so I don't know how long you would have to push it to see adverse results.

I don't think anyone is trying to berate your points because they are valid and you have good info, I just don't know how far the theory really extends into practice on stock machines, especially two strokes. For me it just doesn't make sense to run expensive oil since I change it so often, and it doesn't make sense for me to use race gas since I'm not looking for a boost in performance. For guys who want top performance and longer oil life, by all means run the application specific stuff, but I don't think that has to be the only option for everyone.

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Make Hillclimb Great Again

Ratbeach Racing

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9/24/2015 11:08 PM

Do you honestly think that a casual mx rider will put an engine oil through oxidation, thermal break down, causing it to shear? Imagine running your mx engine for 5k miles, in all types of weather all over the world, with ZERO warm up time. Endless start and stop cycles, idling in traffic, etc (the life of every commuter vehicle oil around the world).

Do you know the typical running oil temperature in a MX bike? Do you know the oil temp in a typical car engine, or performance car engine? Wanna talk about RPM's? Let's watch this consumer car turn 10k plus...

https://m.youtube.com/watch?feature=fvwrel&v=l15l3nTLmhE

And I doubt he's running motorcycle oil. Think about all of the makers of "motorcycle oil", where do they get their raw materials from? They all start with the same product.

You put so much faith into the words "specially formulated". It is important to remember that these "special formulations" were created by men no smarter than you or I.

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9/25/2015 6:28 AM

JH911 wrote:

agree. 92 pump is fine. Non ethanol preferred. If you're looking for performance and consistency throw in 1 or 2 gallons of race gas, but anything more and your just burning $$$. Stock engines are not setup for 100+ octane fuels. If the engine can't utilize it no point in wasting the $$$. Avoid AV gas. I know someone is going to pipe in and say AV gas is all they run and it works fine. That maybe true, but that's just like people who use car oil in their bike. "It's cheaper and works fine." It may work fine, but car oil is not motorcycle oil, AV gas is not race fuel. These items were never engineered or intended for use in a motorcycle. While AV gas is 100 octane and leaded, that has little to do with the energy value or burn speed for which it was engineered. The simplist point is AV gas was engineered to burn at realatively low and constant rpm 2000-5000 just like car oil is engineered to be run between 1000-5000 rpm in most cases. Our bikes idle at those speeds and pull through those rpm ranges sometimes before half throttle!! Why then would put something into your bike that is essentially failing to properly function half way through the job? Leave car oil in cars and leave AV gas in planes, use products designed for what they're intended. Octane has nothing to do with how much HP it will make. It is simply a fuels resistance to detonation and or pre ignition. So more is not always better.

While I agree with most of your points. I think of it slightly different. Think of it in levels, straight pump gas OK, pump gas mixed with av gas better, pump gas mixed with race fuel best. Until you get to race engines, then specifically formulated gas best. But people that will tell you that av gas is just high quality pump gas are incorrect. it is formulated for planes, and even av gas from one area to another with different elevation is different. Planes that fly around Colorado will typically fly higher altitudes than say those that fly around Florida. A 40-50 year old plane is still considered a good plane, there are still a lot in operation. Those engines not only are designed to use lead but also are designed to burn a certain amount of the engine oil. The fuel is designed different for planes. And while in many instances you could replace one fuel with another, most engines are not built and tuned to the performance edge that if will damaging to the engine to not run the best choice.
Having said that, there are some hot rod boats that they recommend using regular gas and not even premium. They are designed to run on the lower octane. Explained this way, the higher octane does burn slower to prevent knocking but it also burns at a higher temp and folks have been known to melt pistons. But a boat motor is constantly under load.
So when they say the gas or oil is all the same base, well all the beer is made with hops right?
And yes the folks that formulate the stuff are smarter than us, maybe not in life but for sure in their craft.
Lastly, as far as car oil goes. I firmly believe that they sell so much of the shit that they maximize their profits not by making the best oil, but by installing the minimal amount of the good stuff just to eeck past the government/industry standards to get their rating. Because yes the additives play a huge roll.

From Cessna Pilots Assn. aritcle. Many years ago, used to fly a 1976 182P
"1956 through 1976 model year Cessna 182 Skylanes can receive STC approval to operate on auto gas. The makeup of auto gas coupled with the Cessna 182 Skylane's induction system produce a couple of interesting operating characteristics. First of all because auto fuel vaporizes more readily than aviation gas it is possible to develop carburetor ice at higher outside air temperatures on auto gas than on aviation gasoline. The amount of ice that is produced remains the same but pilots will notice carburetor icing occurring at higher air temperatures on auto gas than they are used to experiencing with aviation fuel.

TM

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9/25/2015 4:00 PM

Running Avgas in a 05 CR250 and a YZ465. Both run 32:1 Maxima SuperM. No problems over the last 3 years with either. All the technical blah, blah, blah doesn't really mean shit to me. In the real world both bikes run great. The YZ is an easy starter in tennis shoes. The YZ ran awful on California pump gas pinged and rattled and a was hard starter. With no changes except avgas it became a smooth, quiet running machine.

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The older I get, the faster I was.

9/25/2015 7:31 PM

Thanks for all of the replies everyone. I appreciate it! Going to try to run AV gas in my bike and see how it goes.

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