I have a buddy that for the most part got me into ATV riding and I must say I just enjoy the hell out of it. He does all his own work on his and until I got the new ATV he did all the work on my 2000 sportsman. Question is: He is telling me I need to run a higher octane gas. I now only run 93 octane the highest available at any locale gas station but he says I should blend the 93 with 110 racing fuel 1to1. Looking in the book I don't find anywhere were it says this is bad for the unit other then saying I only requires 87 octane. He says it will run cooler and will help with throttle response along with keeping the engine cleaned out. I'm leery of this, one, will it screw with the warranty, two is this engine going to take it. IMO I am satisfied with the performance now and if I wanted a jet I would have bought one. What do you think?

 

If you are satisfied with the performance now, why mess around with using racing fuel? The engine components were designed to work on 87 octane. You could use a higher octane but IMO I would'nt use racing fuel at all.

 

you will not gain any HP by useing 110, in fact you will loose HP. The only way that you will need and benefit from using that high of a octane is if your compression ratio is high enough to call for it. Which on a stock ATV it is not, you will actaully make the most power on 87. The higher the octane the slower the fuel burns, which in a high compression engine you need that so you don't get pre ignition/detonation. If I were you I would just run 87, but running a higher octane fuel will not harm anything , but it will waste money.

 

<div class="FTQUOTE"><begin quote>Originally posted by: 03scrambler500

you will not gain any HP by useing 110, in fact you will loose HP. The only way that you will need and benefit from using that high of a octane is if your compression ratio is high enough to call for it. Which on a stock ATV it is not, you will actaully make the most power on 87. The higher the octane the slower the fuel burns, which in a high compression engine you need that so you don't get pre ignition/detonation. If I were you I would just run 87, but running a higher octane fuel will not harm anything , but it will waste money.</end quote></div>

Bingo....unless you are running high compression or a power adder(ie Turbo,Nitrous Oxide or a Super Charger ) or running the engine on a lean mixture and or have the timing advanced considerably,you do not need that much octane,it will make less power and be a huge waste of money. 110 is on average $7 a gallon around here.
Not sure what your engines compression ratio is,I know they bumped up the CR on the 850XP to 11:1,which a little much for 87 IMO but that is what the book calls for. They must have the ignition timing set up with very little advance. There is no need for more that 93 in that machine stock IMO and I run 89 for peace of mind with the higher CR.

 

as the boys have stated the book calls for 87 for a reason so using higher octang. if its required on certain engines(like my old srx) is because its a requirement for those higher compression engines. my self was putting out 150 psi of compression and would require the higher ocatng to keep it cool. dont waste the money.

 

Exactly what the others have said. Octane rating is exactly that, a rating of the fuels ability to resisit ignition. It has nothing to do with the fuels ability to clean or it's potential energy. In fact pump gas has Deposit Control Additives (DCA) in the fuel, which help to clean the intake/engine, so your friend saying to run race fuel in the engine to clean it out is completely wrong. Race fuel does not have DCA in it and will leave deposits rather quickly in your low compression engine.

 

Why pay for gas with an octane number 15 higher than what you need? [img]i/expressions/face-icon-small-confused.gif[/img]