As gas prices are sky high I am wondering if there is anything wrong with running a lower ocatane gas (87) in the 400EX?

 

as long as it dosnt ping your fine

 

Factory recommends you run premium, and since there's only a $0.20 difference between a tank of premium and regular, I'd just stick with the good stuff.

Don't go by the "if it doesn't ping, it's fine", because as loud as that engine is, it could be pinging something fierce and you probably wouldn't notice it until you burned a hole in the top of your piston... so is it really worth that 20 cents you saved?

 

Motherhead is right as it would be hard for the average person to know what to lisen for. While liveing in mexico a few years ago at a friends summer home I ran some nasty fuel threw all my XR's (same engine in my 400)and the detnation, spark knock and pinging was so loud my friends could hear it 100 feet away. Sounded like the wrist pin berring was missing on a 2 stroke. Never found any pistion crown/head damage either, as i only ran them for a few minutes before draining that junk. I even video taped the sound it was so bad. My manual for my XR says 87 octane but I do notice spark knock if i dump the clutch at low RPM with the cheap stuff.
Joe

 

i've ran 87 in everything i've owned.

I never have any trouble. Even though my blaster has blown up twice. But that was caused by a crack in the sleeve...

 

I run 87 octane in my 400EX, I can't tell any difference between 92 and 87. I can tell a difference with my motorcycle, but not with my 400EX.