Bonneville America Forums Forums Technical Forums General Tech Octane: High Grade or the lower?

When it comes to fuel, gas, petrol - whatever you want to call it...
Do you go for the highest octane, always?
I have always used the highest available...
(except when on vacation, and filling up a rented HD)
Comments?

The dealer told me to use premium only...the RAT site had a bunch of posts saying that 89 octane (mid-grade) is best. Anybody with gas problems out there...the bike kind?

Yeah, well that enchilada.....Oh, sorry......the bike kind!

Roland's right, as far as I know. 89 is fine, though I'm a still a little brained-washed. My dad always told me the higher the octane, the better, so I still only use the "ethyl"(Man, how old am I? That's 91) But from all that I've read and heard recently, 89 is more than good enough for almost any engine and that you're throwing your money away by going for the Premium Grade.

Dwight

Although I'm sure it's not relative, I used 91 until I got a batch of bad gas from a major company. From then on, I stay away from there and just use 89 like I believe the manual states, the bike runs great. jeff

In cars i've had.........milage was always better with high test........sometimes 3-4 mpg.......i use 93 octane in my bike.......she's my baby and she dont drink much...

Mikey, 89 is fine. This isn't a high compression engine, so really no reason to go with premium. And with gas prices now shooting up well above $2.ridiculous a gallon, it's about all I can afford any more. My Passat engine is much more high performance (turbo'd), and even though the manual says only premium, it works just fine on 89, and still get 31mpg on the highway, same as with 92.

If I buy from a station with separate hoses for each grade, I'll buy the 89. If all grades are dispensed from the same hose and I don't know that the previous purchaser bought 89 or 91, I'll go for the 91. Up to 1/3 of a gallon of the previous purchase can remain in the system.

It's personal choice, but.... in my car ('99 Firebird), I get approx. 2 mpg better on Premium (92 octane). Thusly, about 30 extra miles per tank.
My old Airhead Beemers (pre-unleaded)would NOT RUN on anything less tha 92 octane, so I've just continued to burn the highest I can get.

I always go for the 89 octane. However, if I am stuck on the road needing gas, and the only available station has one hose for all 3 grades, I buy premium. Probably, the last person using that pump bought regular grade. With a 4.4 gallon tank, 1 quart of regular will make a difference. Day to day, I avoid the "single hose" pumps.
Dennis
p.s. I do notice a little better mileage with the premium grade fuel. When I siphon fuel from my daughter's VW Beetle diesel, my bike smokes a lot.

This has been discussed quite a bit in the past, but my personal impression is the bike seems to run better on higher octane gas. I try to use Sunoco exclusively, and always go with the next to highest grade. ( forget the number). It will run fine on 89, but pulls the best with hi-test...

The owners manual says 89 octane, but I usually use regular unleaded. My bike runs great on regular unleaded.

You have to remember that our ignition system is electronically controlled, and becasue of this the bike will adjust the timing depending on the type of fuel that you use.

The higher octane gas doesn't mean it is better just that it has a higher octane rating. I have know several people that have operated gas stations. Based on what they have told me, the only gas that you are guaranteed to get at its advertised rating is regular. Plus and Primium gases can be anything between regular octane up to the advertised octane rating. It all depends on how much profit they want to make, or how much gas and what type the delivery truck is carrying.

Tom

I used to use nothing but premium. I didn't get a batch of bad gas, but I got some additive-ladden gas in late spring, early-summer that made my bike detonate like a mofo. My dealer said that the additives used to reduce emissions in winter can really lean out the bike in warmer weather, and since premium doesn't sell as fast as regular, there is still plenty of the additives in the premium, sometimes well into the summer. Then he said run it on regular for a little while - it won't hurt the bike.

Despite all of the accompanying literature, my dealer told me 87. So after I stared in disbelief for what seemed an eternity, I folded. I've been running 87 octane BP, get 50+ mpg, bike runs like a champ and I've had ZERO problems. She probably runs better on British Petroleum!

mikey,
The manual does call for 89 octane but you have to remember this is just a suggestion, same as speed limit signs are.
One problem you will run into usimg higher octane than is really needed is carbon buildup. I use 89 all the time before the big bore and had minimal carbon buildup. Some others I saw ran high test exclusively and had massive carbon build up. I read somewhere, do a google search for carbob buildup, that using high octane gas will not burn completely due to the extra additives sinse the gas is not in the motor long enough in a bike and the motors are relatively low compression rates compared to race machines that require high octane.. Kind of made sence to me, maybe I oversimplified it though. I will now run just the Sunoco 91 octane and will switch to the 93 if I get any pinging. Pinging is the key. If it pings, go up in octane, no ping you can go down until you get pinging than back up. Also depsnds on the brand, I always used Sunoco with the dedicated hoses and als use mobil on ocassion.

I'm going to be the contrarian here. It's been my experience that with both cars and bikes that you get the best mileage and performance out of the lowest octane that will not pre-detonate. For me, that works out to 87 in winter and 89 in summer.

There's a ton of research out there that backs this up. Just Google on octane.

the Speedchannel just had a test concerning fuel octane......they ran a Porsche on a dyno.......with 94 octane then 89 octane......the car lost 5 hp and 10 ftlbs of torque with the cheap stuff........thats reason enough for me...

A more appropriate test would be to run a vehicle 'not' requiring 91- say a mid size, low compresson sedan on 91 and seeing if there was improvement. The Porshe is designed for a high octane, therefore a negative effect of lower octane could be expected.

tcv,
"You have to remember that our ignition system is electronically controlled, and becasue of this the bike will adjust the timing depending on the type of fuel that you use"

Without feedback from an oxygen sensor in the exhaust, how can the bike know how to adjust timing. It has no idea about burn rates, lean- or richness of exhaust, pinging (from a knock sensor which we also don't have), mass air flow sensor or vacuum sensor for intake pressure, etc... I may be wrong, but believe our ignition system is relatively "dumb".

gaspipe, I think you hit the nail on the head, the Bike MUST be run on BP to run properly. Anything else is just sacriledge. Of course, then there is the question of why Triumph only uses Mobil 1 oil that is only formulated in FRANCE!!! You Brits aren't going soft on us are you?
)

I have been in the gasoline delivery business for the past 15 years. What your gas station owner guy said is completely untrue. The octane ratings are government controlled. There are big fines for selling gas that does not meet the octane rating it is sold at. This is one reason it pays to buy only major brands as they will not put regular (87 octane) into premium (93 octane). Small "no name stations" will do this to make an extra buck. But if they are caught there are huge fines.The octane rating is and indication of the fuels anti-knock abilities. If your motor does not knock under a load using 87 octane than go ahead and use it. Mine does.

Quote:

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Point 4 - (This is just my own theory) There has been some small amount of concern about carbon build-up. If High-test fuel retards combustion, and if it isn't a requirement, I wonder if using higher octane may in fact reduce firing efficiency in lower compression engines and therefore contribute to the carbon fouling that some have experienced. Again, that's just a thought with little to base it on - But its my idea and I'm stickin' to it.

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Actually your theory is right on with the facts. What we call octane is really "octane rating". Octane is a chemical component of gasoline, heptane being another. The process, known as cracking, of raisng the amount of octane in gasoline became prohibitivly expensive many years ago, so chemicals were added to simulate the characteristics of octane, ie resistance to combustion. For years the main chemical was tetraethyl lead, hence the term "ethyl" for higher octane rated fuels. Tetraethyl lead is no longer used, that is why it's called unleaded, which is becoming an archaic term since all commercial gasoline has been unleaded for about 30 years.

Since octane rating is resistance to combustion, running higher octane fuel in an engine designed for lower octane will result in incomplete combustion. The key to getting the best performance from your fuel is to burn it as completely as you can without igniting it too soon (preignition) which results in ping.

Flux capacitor...........Fluxing....

Unless you've increased the compression or altered the ignition timing, stick with the mid-grade called for in the book. At best, there is no advantage to using more octane than needed. Since higher octane lights off slower, it could cost you a slight bit of power and increase carbon buildup.

BUT, if you have to choose between the expensive stuff or low octane camel pee at a 2 pump station, go with the good stuff, as too high octane rating won't cause the problems that too low will.
Don't try mixing high and low in hope of getting mid grade. Unless you are a petro-chemical engineer, there is no way to know what proportion is correct because the chemical aditives may not be the same.

This of course all coming from a guy who miss-spells:
"carbureted" - take it with a grain of salt! <g>

I experimented with different gas grades. I got consistently better milage with the higher octane fuel then I did with regular unleaded and they are right, she doesn't drink much so I use the super unleaded gas. Nothing but the best....

I personally noticed that my bike seemed to lose a little
performance running on 93. I was running it because here in
SW PA we get oxygenated fuel for emisions from June 15 till
Sept 15. Some of the power equiptment I have worked with
advices using the next higher octane of oxygenated fuel so I
figured I would do this with the bike also. When I was out
last year I went back to the 89 and noticed the bike ran
better. I then thought back to my racing days and remembered
that we decreased octane until we had a problem and then
went back up. We ran cars on pump gas through 130 octane
AVgas. You can see 1/4 mile times change when you need more
octane but once you had enough octane more wasn't going
to make you any faster. More octane won't give you better
performance unless the engine needs it.

After reading this string of posts, I decided to run some regular (87 octane) through Vera. First two tanks I actually got 12 & 15 miles more out of each fillup, compared to mid grade fuel. Now, into my third tank, I am noticing that parallel twin "ping" that is as distinctive as an AK47 in comparison (if you heard it, you won't forget). Don't want to disagree with anyone, but I am going back to 89+ octane.
Dennis

Aafter I spent $2.59 a gallon for hi test I say it runs better. When funds are low it runs really good on the cheap stuff.

I found the following on the www.



Do you really need Premium Gas!

Don't be gulled by slick oil company marketing ploys about the benefits of premium fuel; few new cars or motorcycles really need it and those that don't won't run any better for using it.

There's no mystery to it. Just look at your owners manual; it will tell you the manufacturer's fuel recommendations. There may also be a sticker on the gas cap or even on the instrument cluster under the gas gauge. Whatever it says, abide by it. You're only wasting your money by burning premium fuel in a vehicle that doesn't require it. Higher octane (91 and up) gas burns more slowly and will actually give poorer performance when fed to engines that were designed to burn regular 87 octane fuel.

So what happens, on the other hand, if you use regular or even mid-grade gas in a vehicle that needs premium? If the vehicle in question is a late-model one, nothing that will cause any permanent problems. The computer will adjust the ignition timing and other engine parameters to compensate for the lower-octane juice. You may notice a slight fall-off in acceleration, but no engine damage or driveability problems should arise.

But with some older, pre-computer cars (model year 1981 and before) you could have a problem. For example, a '60s "muscle car" with high-compression pistons must have premium fuel to avoid deadly engine knock (pre-ignition), which occurs when the gas and air inside the engine's cylinders ignites before the piston reaches its firing position at "top dead center." When that happens, the explosion tries to force the piston down when it's coming up, putting enormous strain on engine bearings, connecting rods and the relatively fragile aluminum pistons themselves.

Unless you want to ruin your high-compression engine, premium fuel is an absolute must in such cases. You may even have to add a can of octane boost to each tank in some cases to bring the fuel up to spec.

Premium fuel prevents engine knock because it is less volatile and hence burns more slowly than lower grade gas, so it is not as susceptible to pre-ignition.

However, even today's "ultra" premiums come nowhere near the octane level of the what was available 30 years ago. In those days, octane ratings of 100 were common; today 94 is the best you can get--and the octane level is raised not by lead but by the addition of "aromatics" that may cause problems in older engines.

Fortunately, very few cars on the road today have high-compression engines that need such fuel. The handful that remain have usually had their engines rebuilt with lower-compression pistons to run on today's lower-grade gas--and the others can avail themselves of octane boosters readily available at auto parts stores.

You should not buy octane boosters, however, for use in an emissions-controlled car with a catalytic converter. Octane boosters may foul the converter and eventually plug it up. Besides, no factory-built model produced since the early 1970s needs the stuff anyway. You're just wasting money and buying the advertising hype.

There is one thing, though, that could cause your late-model, regular-fuel car to need a higher grade gas: age. As an engine gets older, carbon buildup on the tops of the pistons effectively increases the compression ratio, which in turn means you may find that the car knocks when you use anything but mid- or even premium-grade gas.

What are people using who own 60's - 70's Triumphs? If I remember correctly the 70's Bonnevilles recomended premium leaded gas. Premium leaded went away at the pump many years ago. Are there aftermarket additives available?

i alternate.

prices go up fast but take a long time to come down.

cat

Gibson, not to disagree with the Speedchannel, but I've got 4 years experience that says the low grade doesn't make much if any difference in a high compression engine. Admittedly, my engine isn't quite the thoroughbred that a 911 engine is (although it is only about $2500 away from being able to put out the same HP as a stock 911 Carerra), but has almost the same compression (mine is 9.5:1, a Turbo S is 9.4:1) I've got a turbo 1.8T VW engine, that requires 91 minimum, and decided to try 89 some time back. I've never seen a reduction in performance, or mileage. When I take long trips, I used to normally run 91 or higher, and got 31.5mpg cruising steady on the highway, and 24.5 around town. Later after switching to 89, the mileage stayed the same, 31-32mpg. Acceleration (admittedly seat-of-the-pants) does not feel any different.

"prices go up fast but take a long time to come down"

Cat, that is because of the philanthropic nature of the oil companies (and big business in general). By slowing the fall of oil prices at the pump, the oil companies are shielding us from the unpleasant "sticker shock" that comes with rapidly changing prices. They know that we are already accustomed to high prices, so if prices jump up higher fast, it's no big deal, everyone is used to and expects it. But drop the prices 30cents a gallon, and imagine the psychological effects it might have on the general population! Thank goodness they are there to protect us from such a calamity...