When Hi Test Not Available...

Occasionally I run very low on gasoline in an area where the local stations don't carry premium. Since I've not seen any reference to a knock sensor on the WR250R I assume there is no provision for an automatic spark retard if a lower test gas causes knocking. Two questions: has anyone run regular or mid-grade (87 and 89 here) with no ill effect, assuming the right wrist is calibrated to the situation, and has anyone found an octane booster effective in mitigating knock on non premium gas?

Just bought a 2008 wr250x a couple weeks ago. I had no idea it required premium. I put close to 400 miles on it using regular without hearing any knocking or it running bad. Of course now I know and I have been putting premium in it. I doubt it would mess anything up unless you always put regular in it.

I put premium in when it is available... when all they have is regular I go that route and don't even give it a second thought.

Haven't really noticed any difference in performance between the two.

I routinely put mid grade in mine (89 octane) to no ill effect over 12,000+ miles. I used regular for a short while until I heard what I thought was a single knock going up a hill in a high gear at low rpms with about 3/4 throttle. Coulda just been a rock hitting the case but it scared me enough to make me start using mid grade.
Use some common sense though. If you are at a high volume gas station with fresh gas you can probably get away with mid or even regular (still not a great idea). If you are at a craptastic station out in the sticks get the best they have because it may all be old, which reduces the octane rating... and if you have to use regular, avoid high load at low rpms because if its going to knock, that's when its going to do it.

I run mid grade, haven't had a problem.

My right wrist doesn't give two craps what octane gas goes in the bike.    


Don't worry about a thing.... keep riding it like you stole it.

You know I am kinda amazed at the responses. This is the same forum where everyone seems to change their oil every thousand miles or less with full synthetic and then changes the filter every oil change right? Even though the repair manual calls for 3k oil non synthetic and 6k on the filter. Shouldn't we then be suggesting race fuel for these bikes? Especially since the damage done to an engine can be instant and catastrophic when running to low of an octane.

I am under the impression that over the counter octane boosters does in fact work, I don't have a brand to recommend though. On the plus side one little bottle will last a long time with these teeny tanks.

beee wrote:

You know I am kinda amazed at the responses.  This is the same forum where everyone seems to change their oil every thousand miles or less with full synthetic and then changes the filter every oil change right? Even though the repair manual calls for 3k oil non synthetic and 6k on the filter.  Shouldn't we then be suggesting race fuel for these bikes?  Especially since the damage done to an engine can be instant and catastrophic when running to low of an octane.

Not everyone here is as anal as you make us all sound.   

I change my oil about every 4000-5000 miles, and I do the filter every oil change.

In the USofA, and at sea level, I doubt the difference between 87, 89, and 91 octane is really all that.

If the vast majority of all cars produced can run 87 octane, why would anyone expect "catastrophic" damage from a de-tuned, highly restricted, 24 horsepower engine simply from using 87 octane???

beee wrote:

You know I am kinda amazed at the responses.  This is the same forum where everyone seems to change their oil every thousand miles or less with full synthetic and then changes the filter every oil change right? Even though the repair manual calls for 3k oil non synthetic and 6k on the filter.  Shouldn't we then be suggesting race fuel for these bikes?  Especially since the damage done to an engine can be instant and catastrophic when running to low of an octane.

I am under the impression that over the counter octane boosters does in fact work, I don't have a brand to recommend though.  On the plus side one little bottle will last a long time with these teeny tanks.

The manufacturers work off the idea that you may buy old gas from a podunk station and then lug the motor while you ignore the knocking like a doofus. Still people wait until someone brave says "I ran 89 for 1000 miles and it was ok!". Then you think... hmm... It obviously wont instantly implode... ill try it too. You listen for pings and knocks at lugging speeds and when you never get any you relax. Mission accomplished and money saved. Ive probably done 5,000+ miles on mid grade without a single knock. The knock I think I heard on low grade happened going up at hill at 40mph in 6th, so if I had to I wouldn't think twice about running 87 and just being mindful of my rpms vs load. Also, I know head design and valve overlap influences things, but I think they over rated ours a bit. My ZX6R has 13.3:1 compression and recommends 90 octane vs the 91 octane recommended for our 11.8:1.
Also I only change my oil every 3-4000 thousand :P though I do change the filter every time out of habit and not being able to remember if I did last time or not.

What is the knock from, and how does low octane fuel cause it>?

Knock is when your fuel air mix goes off early and fights the rotation of the motor. It literally sounds like a hammer just hit the top of your piston with a knock or ping, because it pretty much just did. Often sounds like a rock hit the motor. Cars have sensors that detect knocks and retard the timing as well as maybe riches up the fuel mix to stop it from happening. Bikes don't.
Octane rating is volatility. The lower the rating the less stable the fuel is. Boyle's law, when you compress a gas it gets hotter so the fuel air mixture gets hotter and risks spontaneous combustion as you rapidly compress it. Then if there are any hot spots in the chamber it gets even worse.To run higher compression ratios and more advanced timing you need a less volatile fuel to keep it from going off before it's supposed to. That's pretty much it. Modern motors get away with a lot more compression and advance because they design the heads and piston tops in a computer to let them get away with more. In the old days you needed premium at like 9:1 compression lol, now days with a good computer designed head you can get up over 13:1.

So the flip side to the OP, the few places closest to me don't have 91, but do have 93. Is there any issue to running this even though 91 is suggested?

It won't hurt anything but your pocketbook. Might make some tiny tiny bit lower power due to the slower burn but a dyno probably couldn't even notice.
On cars it will sometimes make more power though, they will sometimes advance the timing but not always. Cars made to run on premium will definitely make more power on it.

Good to know, and with our huge gas tanks I think the difference is about 12 cents, Ilike to live large, I can swing it, lol.

I have used these with some success. I ran regular gas in my WRR this weekend in hot weather at high elevation. I think it ran hotter and it actually spit at me one time at 70mph (knock?). I will carry these in the future since many gas stations in remote areas of eastern Oregon only have regular.

I've always ran regular and not a ping or knock. Plenty of power too. I'll have to treat it to some premium and see how much power is gained.