Race Gas Vs. Premium Gas Whas the deal???

Another side note on race fuel, it runs COOLER! The higher octane fuel has a lower flashpoint, i.e. it ignites at a lower temperature...meaning the engine also runs at a lower temperature.


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat.

Kevin, that is a very common misconception. Race fuel *may* let your bike run cooler but that might be due to jetting differences from a number of factors with the fuel (specific gravity, distillation curve, reid vapor pressure, etc). There is so much that goes in to a race fuel that virtually all generalizations should be ignored. Since you can get a race fuel in so many different formulations to suit so many different needs, you can get a fuel to do just about anything you need.... IF you know what to look for.


MX Tuner

I have a stock WR400 and was wondering is it worth paying the extra few bucks for a race fuel mixed with premium or would preimum do the job. My bike is stock and Im mainly doing trail riding.

I run premium unleaded in my '99 WR400 - I'm dual sported so I really want to be able to fill up anywhere. Race gas is blended more consistently and will usually allow you to optimize jetting w/o worrying about variations in fuel blend. Check out www.dirtrider.net for lots of info on race gas.


Socal, This is a good question. You will find many different opinions here regarding race gas VS. pump, I can only speak from my own expierences. I have a stock Canadian 426 and was curious too if race gas would help so I tried race gas once and found it to be a total waste of money. If my bike was heavily modified it might take to race gas but as it sits pump gas works better for me. I must speak for our friend "Taffy" and tell you to try it yourself, you'll never really know until you test it yourself. Just put a gallon in and run the beast. It's only a $3.00 commitment. Best of luck


I read that in a tech article, about the cooler engine temps, although it does make sense.

I have read several magazine articles not run race fuel in these bikes...[???]


you *CAN* see some real gains by using a good fuel (like VP C12 or MR1) and jetting it to take advantage of that fuel.

my 250F has NEVER seen pump swill and it never will.

plus, i *KNOW* i won't have any combustion problems in deep sand or mud.

Thanks for all the info, I think I will continue to run premium she seems to like it. I was just wondering if it would hurt my bike or cause premature engine problems.

Originally posted by NH Kevin:

Another side note on race fuel, it runs COOLER! The higher octane fuel has a lower flashpoint, i.e. it ignites at a lower temperature...meaning the engine also runs at a lower temperature.

Ok, let me straighten this out before it gets going for too long. The OCTANE rating of a fuel is an indication of that fuel's ability to RESIST, yes RESIST burning. The higher the OCTANE number, the MORE RESISTANT the fuel is to igniton. Why do we need this? Higher compression engines, or one's that are also timed closer to TDC, require the fuel to still be in vapor form (i.e. not auto-ignited) when the spark is delivered to the cylinder. The higher the compression, the more heat produced in the cylinder (an increase in pressure also increases the temperature). If that increase reaches the temperature of the fuel's flash point, then the fuel will auto-ignite (or detonate, as you might hear from motorheads). So, you must have a high enough octane rating to keep the fuel from igniting prior to spark delivery. If your engine is detonating under normal use, use a fuel with a higher octane rating (and therefore HIGHER flashpoint). BUT, if your engine is running fine on 93, putting 108 into it will only cause you to spend more money for your gas (speaking from a purely detonation / octane rating viewpoint). You get nothing out of it. If you really wanted to know what the performance gain possibility was, get ahold of the manufacturer of the race gas and find out what the specific internal energy is and compare that to regular gas. I think you'll find that they are almost identical.

*plink, plink* my two cents.

Originally posted by Butta:

Ok, let me straighten this out before it gets going for too long.

Butta, I'll add two more cents to this...

Using higher than needed octane can also result in less than complete combustion of the fuel (because as you say, it's a little harder to ignite), which in turn can lead to excessive carbon deposit build-up in the combustion chamber. This is a viscous cycle in that the deposits raise the compression ratio which eventually may REQUIRE the higher octane fuel to prevent detonation. A worst case scenario may involve the piston and/or valves having trouble moving freely due to this build-up.

Because the combustion may be less complete when running more octane than needed, you're also probably making less power than you could. The general idea is to use an octane level that is barely high enough to prevent detonation.

Jerry in Deltona, FL

BE aware also that serious race fuels like VP MR-1 and Neutek fuels are heavily oxygenated and are EXTREMELY corrosive to almost everything they come in contact with, so when you run those types of fuels you need to burn it ALL and NOT leave any in the tank or carb after the riding is over. Also MR-1 is around $15.00 per gallon depending on where you get it....not very cost effective on the "trail".


01' WR426,YZ timing,EMP #2,#48Pilot,#100PAJ,#172 Main,BK mod,stock pipe-no baffle, open airbox,Gray-Wire Pulled,K&N Filter, throttle stop mod,CA Street Legal,Pure SuperMotard 17 in. wheels, 15/46 gears,ProTaper bars,

Those frickin' MAD Magazines obviously are not chock full of entirely accurate race fuel techno stuff like I have been lead to believe! :).

Now I have to find my technical instruction from other sources...!

Just remember the mags are written by editors that translate for the tech heads. Octane is not the fuels resistance to burn, it is the *anti-knock* ability of the fuel.

Big difference. Knock is caused by pre-ignition, This means ignition by means other than a spark plug. As compression goes up, the chance for pre-ignition (also called auto-ignition) goes up. Octane helps eliminate this.

Due to substantial differences in formulation. nobody should expect to get a performance gain from simply pouring race fuel in their tank without rejetting.


MX Tuner

What the Hell.....I use 108 Octane fuel in my WR for trails and for Motocross. I've had the lid off twice and everything looks great. I can tell a major difference in throttle response between 97 octane and the 108 I use now.....Power IS Everything....beyond that why does it matter ?

Bonzai :)

dammit!! i hate it when i pre-ignite, it just messes everything all to hell!


I think you are right. For trail riding, premium pump gas should be fine. I would only suggest racing fuel if you are....well....racing!! Trail riding does not put the load and heat into an engine like racing does.



Life is too short, work hard...play hard

Sponsored by Yamaha of Cucamonga and Larry Roeseler's Stroker Fourstroke Speed Equipment

Just an FYI guys, for those who are confused by the multiple answers to SoCal's question, the octane rating of a fuel is " a fuels resistance to DETONATION". Pre-ignition is exactly what it says.....fuel is being ignited PRIOR to the engines timed ignition event sparking the fuel(between compression & the power stroke, right before TDC). Pre-ignition can be caused by any abnormal hotspot in the combustion chamber or by compression itself, in the case of some diesel engines. Unless you have modified your WR's engine internally(ie; higher compression, more aggressive camshaft lobe lifts and durations, etc) 92 octane premium fuel is the most efficient way to fuel your machine. Just my two dollars worth(almost the cost of a gallon of premium these days) :).


Y2K WR400FM,Answer top tree w/Accu-Trax clamp,Pro-Tapers(CR-Hi w/ EE handguards),Devol Rad. & frame guards, Guts tall soft foam w/ ballistic cover, 14/52 w/DID VM X-Ring, Kouba-T,Michelin M-12's ft.& rr.,12 oz. flywheel weight, Zip-Ty Racing Link & Shark Fin, Cycra front rotor guard and T.M. Designworks Chain guide, buffer & chain wheels. Street legal except for the non-"DOT" tires.

[This message has been edited by BlueThunder (edited September 27, 2001).]

If you would like to learn about fuel, go to www.off-road.com/dirtbike/. Go to the back issues and open May 2000. There is a two part series by Rick "Super Hunky" Sieman of Dirt bike fame. It taught me more than I wanted to know.

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