Jump to content
Sign in to follow this  

Is 100 octane fuel ok?

Recommended Posts

I am picking up my new '04 X on Thursday.

I am used to running 100 octane fuel in my RM250. Can I do the same with my X?

It's sold at a local Unocal station, and it's about $4.00/gal. I don't mind the extra expense...

It smells so much better than 91. And I imagine the bike will be running cooler?

Share this post


Link to post
Share on other sites

Hey, If you are going to spend $4.00 a gal. anyway, I suggest you go to your local bike shop that sells race fuel like VP-110 octane and get your moneys worth. My X is almost 8 months old, has never had a drop of anything but VP-110 in it, Honda oil in engine and gearbox, frequent oil changes, TwinAir filter w/backfire screen removed from day one, no abnormal oil consumption. I did not cut out the airbox and I have the JD jet kit. Valves are still perfect. Just rode 37 miles today. Broke it in like I stole it. Either I am just lucky(not) or I have benefitted from the clean air and keeping the revs lower as I DID NOT do the pink wire mod. Compression ratio will affect engine temps when running high octane race fuel. The CRF-250s are high enough CR to benefit from race gas, but everyone seems to do fine on pump gas. Clint

Share this post


Link to post
Share on other sites

you guys really are wasting your moeny and not doing your bikes any good.....too much octane in a four stroke can be bad for it....i run premium at my local gas station (93 but it can vary)..if you run anything other than that your wasting your money or being cheap if you get anything under that

edit: But if your doing some racing then i would suggest getting VP Ultimate Four...it has a higher oxygen level and can give you a few extra ponies but its expensive

Share this post


Link to post
Share on other sites

The premium unleaded here costs around $2.50/gal on average, and it's only 91 octane.

It seems like cheap insurance to me to buy better fuel to keep the bike from detonating, and to have it run cooler. If the bike gets 30+mpg, I don't care about the extra $$$...

After all, I've been using premium in my Land Cruiser for 4 years at 12 mpg.

By the way, how could too high octane hurt a 4-stroke? After all, isn't the octane rating referring to the fuel's resistance to detonate?

Share this post


Link to post
Share on other sites

Unless you've done some sort of modifications to your bike, like higher compression piston, then you're wasting your money. Not to mention some pony power. The higher octane fuel will burn cooler and that will cause the loss in horse power. These bikes are made to run their best on high octane pump gas, anything else you're cheating yourself.

Share this post


Link to post
Share on other sites

You don't say what altitude you ride at, but I would use the 100 octane, good gas is good insurance against detonation. It is certainly not going to hurt your engine. On the other hand, using "Pump" gas of unknown quality, might. Given the unidentified causes of valve issues on the X, if I had to choose between "Pump" gas and Union 100 octane, I would er in favor of the 100.

Share this post


Link to post
Share on other sites

The manual states that pump gas is "recommended". I've never run anything but 93 and it's running perfectly. I actually think higher octane fuels, while they may burn faster and leave a bit less residue, cause unneeded strain on your engine.

Share this post


Link to post
Share on other sites

There has been alot of talk on the drz forum that leaded fuel is a good way to avoid valve recession... that 100 octane stuff is not leaded. get some 110 leaded stuff and mix 50:50 with pump gas.

Share this post


Link to post
Share on other sites

There has been alot of talk on the drz forum that leaded fuel is a good way to avoid valve recession... that 100 octane stuff is not leaded. get some 110 leaded stuff and mix 50:50 with pump gas.

That's what I heard too. I am running Sunoco Leaded 110 50:50 with 92 Premium pump gas. IMHO it is worth the extra $$$ if it helps prevent valve recession.

-Fiddler :cry:

Share this post


Link to post
Share on other sites

"Unless you've done some sort of modifications to your bike, like higher compression piston, then you're wasting your money." Hmm,...well I guess I am just an idiot. Now I know that the stock 12.9:1 CR is really a low compression piston. I should have known that race fuel only benefits engines that have upwards of 14-15:1CR. How stupid of me. Thanks for setting us all straight on this. We can all stop wasting our money now.

Share this post


Link to post
Share on other sites

The purpose of the higher octane fuel is to prevent detentation. With a bike as quiet as the Honda, particularly the X, the sound of detentation should be quite evident. If you're using the recommended 91 octane or higher fuel and don't hear detention then no further attention should be required. As "Tuner" mentioned in an earlier post, higher octane fuel burns slower with less explosive force. It will not deliver increased power.

Share this post


Link to post
Share on other sites

"Unless you've done some sort of modifications to your bike, like higher compression piston, then you're wasting your money." Hmm,...well I guess I am just an idiot. Now I know that the stock 12.9:1 CR is really a low compression piston. I should have known that race fuel only benefits engines that have upwards of 14-15:1CR. How stupid of me. Thanks for setting us all straight on this. We can all stop wasting our money now.

Okay Tweedle-Dumb, if you took the time to read then you would know what I'm talking about. Yes, a 12.9:1 compression is high... by normal standards, but not for a CRF. As you should know, that's normal. The engines are designed to take that compression. If you drop in a high compression piston, like 14-15:1 then you will need to run the higher octane fuel to prevent detonation. If you're not getting detonation, and you shouldn't be, off of the 91-93 octane pump gas, then why waste your money? If you have it to waste and it's burning a hole in your pocket, then have at it. The more power to you there Skippy. :cry:

Share this post


Link to post
Share on other sites

Nobody has mentioned the benefits of race gas that convinced me to run it in my four stroke. Most race gas has a small amount of lead in it that I've heard (no personal proof) is good for lubricating valves and valve seats. Also, I can vouch for this from experience, race gas burns so much cleaner than pump gas. On my two strokes especially, I notice much less carbon buildup on the head, exhaust port, and exhaust pipe. It is so significant that on pump gas carbon can build up on the compression side of the ring and wear the bridge between the exhaust ports, necessitating a cylinder replate.

Share this post


Link to post
Share on other sites

I'm not looking for more power, just longevity. I don't have a huge amount of experience with bikes, but I've been racing nitro R/C cars for years. I know what happens when they run too lean- it leads to detonation, and kills the piston.

I imagine the same thing will happen in a gas motor. And from what I've heard, the CA models are jetted way lean. I don't mind spending a coupe extra $$$ in order to skip a premature repair.

Pump gas around here is terrible. My Acura GS-R ran far better when fueling outside of CA (Nevada and Oregon).The car was slightly massaged, but not much. I didn't think gas would make a huge difference, but it did.

So I figured if there's no harm in running much better fuel, I'll do it.

Share this post


Link to post
Share on other sites

stop right there....dont use that fuel....This is straight out of the May 2004 issue of Motocross action mag. On page 48 there an article called Four-Stroke tricks and traps. It says quote "Four strokes don't need high-octane fuel like hugh-strung two strokes. In fact, thumpers run worse on high-octane fuel instead of better. Every manufacturer tunes its ignition, jetting and combustion chambers to accept 91-octane gas. Any higher than that is a waste---untill you start raising the compression." So there you have it....so if you still INSIST on using higer octane fuel be ready for less performance and more cash out of your pocket...

Share this post


Link to post
Share on other sites

Well gee, looks like I'm not as full of crap as some people on this forum seemed to think. Who would have known? :cry:

Share this post


Link to post
Share on other sites

This has been an interesting thread. Lots of myths, and some truths. Here are some facts. Higher octane fuels actually burn slower than low octane fuels, so if all other factors are kept the same, the bike with the lower octane fuel will make slightly more power. The advantage that higher octane fuels give us is; 1) if there is a detonation problem (ie the fuel air mixture exploding instead of burning hence the highest combustion chamber pressure occuring on the up stroke of the piston) it will make the mixture burn instead of exploding. 2) because of the controlled burning nature of the high octane fuel, the savy tuner will be able to lean out the mixture more to get that last little bit of power, and he will be able to advance his timing more to get more power yet. With these mods and low octane fuel the tuner would not be able to rely on the highest pressure point in the powerstroke happening when the piston is moving down. It could happen when the piston is still moving up, this would be detonation.

So in summary, if you are using racing fuel in a bike not tuned for it, you are wasting your money, and making slightly less power. If you are willing to always use the same quality of racing fuel and tune your bike to this fuel, you will see increased power. On a stock bike use the fuel the manufacurer recomends.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×