octane comparisons

The common misconception is that the higher octane means more power, it doesn't. It is only a measurment of the fuel resistance to knocking. Think of it in terms of how quick it lights off. The bikes engine is "optimized" if you will to run on regular pump gas, to fill it with Super is a waste as it has no benefits. There might be a slight benefit to not using Super as it might be completing its burn too quick. But that is stretching it.

People are constantly saying that a higher octane gives you more power or mileage -- neither is true on a stock engine. Now on a tweaked engine, you may be able to measure a difference on higher octane or race gas.

Look at Ethanol, octane rating of about 105 usually, but you get about 2/3s of the mileage out of it as you do regular gas. Something they don't put on those "flex-fuel" vehicles they sell.

 

I'm constantly telling my customers and friends that its a waste of money to buy premium for their bikes. Usually I'll get the same response every time, "Well, I can tell a difference". Drives me crazy. I have also worked on older XRs that will not run good at all on anything but 87.

 

That's alright reg we love beating dead horses. I've been doing some reading about this online. Let's see if I have it right.

Octane rating refers to the gasolines resistance to pre-ignition. Higher octane; higher resistance. Lower octane; lower resistance.

Pre-ignition can happen in high compression engines. Lower octane fuel is more likely to pre-ignite in a high compression engine.

My best guess is this; each persons motorcycle has slight variance in the comp ratio due to wear cond of the engine. Not every engine is exactly the same.

Could be slight variances in engine timing.

Another factor would be climate. We do not all live in the same part of the country. This would affect the air mixture *(ie. altitude, humidity).

All of these factors in turn would affect combustion.

This might explain a certain bikes (like or dislike) of a particular grade fuel. Does this sound right? Or am I just rambling?

My bike seems to run better on 92 than 87.

 

I've seen this same argument on other forums and they all come to the same conclusion: It is a waste of money to use anything other than 87.

That being said and I know this is against all the logical arguments here but on both my bikes I noticed slightly better idling when using higher octane and that may be explained by many other factors that I am not aware of.

One thing I would like to mention...and it seems that no one takes this path as an argument for or against higher octane...is Engine Longevity.

I'm not an expert by any means, however, I believe the true benefit of higher octane gas is not the performance enhancement but how clean it burns. Someone mentioned that it burns faster...and I'm inclined to agree. It also burns more, thus leaving less deposits behind to buildup on the valves and etc.

Maybe someone with more knowledge can explore the differences in longevity between octanes?

 

Ok...did some research on Octane Ratings and engine longevity and found that there is not any scientific proof that proves or disproves that Higher Octane improves performance or engine longevity.

This point is made abundantly clear when the Federal Trade Commision sued Unocal for false advertisment and won (well settled out of court). Apparently Unocal made claims to better performace and/or engine longevity without scientific proof. Below is a snipt of the artical i read about Unocal...the story as a whole can be found at:

http://www.ftc.gov/opa/predawn/F93/unocal-leo.htm

The proposed consent agreement to settle these charges,
announced today for public comment, would require all three
respondents to have competent and reliable scientific evidence to
support any future representations about:
-- the superiority of Unocal 92 or 89 in providing engine
power or acceleration for any car;
-- the superiority of Unocal 92 or 89 in prolonging engine
longevity; or
-- the attributes or performance of any gasoline with respect
to engine power, acceleration, longevity or any other
performance characteristic.

 

There you go reg.... Just put gas in it and RIDE!:tongue:

 

Here you go Reg...all the information you need to know about Octane:

http://auto.howstuffworks.com/question90.htm

 

should be no issues with longevity of the engine, all of the major gas companies use the same detergent package across their entire line -- something missing from their advertising.

Doesn't directly apply, but I took a '94 Toyota Camry to 238,000 miles. It always used regular.

All of the major car and motorcycle magazines all say if your vehicle doesn't specifically require it, use the lowest grade availible. Unless you notice pinging, which shouldn't happen on a modern car engine anyway.

One of the motorcycle mags, maybe sport rider, did a test a couple years ago -- on a dyno. Couple different street bikes, and a way tricked out bike. Ran them all of them on regular, super, and VP (?) race gas (the stuff some dealers sell in the blue can). The street bikes ran the same on the pump gas, I want to say slightly worse on the high octane race gas. The one with the modified engine did run slightly better on the race gas. Worth it on the track, not on the street. If your engine is unmolested, use regular pump gas from a busy station (to ensure their tank see constant re-freshining and turbulance).

Spike

 

One comment on the octane issue. Some new engines have variable ignition advance programmed into their computers. My Toyota Seinna being one. With higher octane fuel the timing gets advanced, more advance more power. On the Sienna I believe that its about 5-10% difference and is quite noticable. I do not know whether or not this applies to the VFR but I don't believe so. I have tried both on my viffer (gen 6) and have not noticed any difference. Can't really comment on the cleaner burning properties of higher octane although the bike shop recommends the ocassional tank of high octane for that reason.

 

4Runner & MDX too

I can notice a *slight* difference in low end torque between 91/93 and 89 octane gas in my '03 4Runner. But I can feel a distinct performance change between super and 'hi-test' in my wife's Acura MDX. The owner's manual of each vehicle recommends 93 octane for them, but having read that most vehicles made after '02 are flex fuel vehicles, I've been putting 'special' in my truck and saving a few cents per gallon, especially since my 'Toy' handles almost exactly the same.

 

I believe the power increase you are referring to is more a function of the advanced timing and less of a function of the octane grade. For example: I put a 5 degree ignition advancer on my Katana (which is carburated ...not fuel injected...so there is not a fancy varible timing set up) which resulted in better performance without a change in octane grades. The increase in performance comes from the fact that the combution chamber holds the burn longer (before the exhaust valves open). I eventually took off the advancer mostly because of the increased heat generated. Because it holds the burn longer the engine experiences a 10%-15% increase in heat....and here in Texas in 100 + degree weather it brings the engine dangerously close to overheating and etc. I did not want to risk damaging the engine.

The advanced timing also moves the power band down on the RPMs. This results in a increase in low end tourq. Again, this is more a function of the advanced timing...and less likely as a result of using higher octane.

 

gotta be careful how you word it, "flex fuel" implies something entirely different, usually meaning a vehicle that can run on multiple different fuels, the most common by far of late being cars & trucks that can run on E85 Ethanol or gasoline. GM makes quite a few, Ford has made quite a few over the years. I know of no bike manufacturers that offer that capability. Not that it really matters, in most of the coutry E85 is pretty rare and hard to find. Very few owners of such cars and trucks ever use E85 in them.

 

The reason you can advance the timing is that higher octane fuel is more resistant to pre-ignition. This is also the main reason high compression engines require high octane fuels. Like all of these issues there are a large number variables. In general it is best to use fuel with the octane rating the manufacturer recommends and generally no advantage in using higher.