What is the best gas to run?

Sorry if this post is out there already... I couldn't find it. So I bought a 400 recently and the P.O. used strictly 91 octane in the bike and never had a problem. I know it is supposed to run 95 or higher. So if my bike runs fine on 91, is there a reason I should start using the race gas? Is it meant for better performance, or is it hurting the motor even if it does not ping or knock? Thanks.

Well, its like this.... Higher octane fuel is more resistant to detonation. If you are not detonating on 91 octane then running a higher octane fuel will just be a wast of money. Are you at sea level? at sea level motors run at a higher compression and therefore usually require a higher octane to prevent pinging. Up here in Utah, 91 is the highest most gas stations carry, where as back in Florida everywhere has 93. I'm sure Yamaha is just covering their butts by saying to run no less than 95. Alot of people think that higher octane means more power. This is not true. Higher compression motors make the fuel mixture pre-detonate and therefore need higher Octane fuel to prevent it. A better way to look at the whole scenario is that you do not gain HP from higher octane fuel, but rather loose HP from pre-detonation by using too low octane in a high compression motor. My 2 schillings

I just run the best gas I can buy at mobil in my 426. Runs like a top, never had a problem in two years. I just wouldn't trust some no name gas stations 91 octane gas, just be sure you go to a respectable gas station that will have a good quality gas and pumps. Mobil, Shell, etc.

Sounds good to me. I ride from sea level (Pismo dunes) up to 1000 feet and have never had a problem. I guess if it aint broke, I won't fix it. Does the theory that better gas does not make more power apply to 2 smokes as well? I have cr friends who swear race gas makes a huge difference.

i run sunco 104 octane its the best

I run premium for the gas station on the corner. I think that it is 91 octane. No problems.

The manual has octane requirement of ~95 octane, (manual is at home, I'm at work just in case I'm wrong) but there was a post I recall that pointed out that the octane rating in the manual was not calculated the same way octane is calculated in the US. Something like metric vs. inch.

The point is, I remember a post that suggested that the US 91 octane rating was close to the 95 octane rating in the manual.

Don't know if anyone else cares, and WR don't use that much gas, but I still don't want to pay for something I don't need.

This quote is from another thread from some guy that seems like he knows a little about these bikes... :thumbsup:

My manual says to run unlead minimum of 95. Every station I stop at only runs up to 93, so that's what i've been running (400mi). No problems but curious as to what others run. I thought about throwing some octane booster in there put didn't want to scorch my bike just yet. Thoughts?

item #1 on the thread entitled "NEW OWNERS PLEASE READ", which is permanently affixed atop the thread listing...

http://www.thumpertalk.com/forum/showflat.php/Cat/0/Number/350540/

jim aka the wrooster

'01 wr250f

By the way, that's out of the 250f forum.

Also, here's #1 from that faq.

1) the manual says to use fuel that is 95 RON. in the usa we use the (RON + MON)/2 method and is what the 93 on the pump represents. pump fuel is adaquate.

Why don't we have one of those faq's in this forum?

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