gasoline

[Nooner]

Does the octane rating on the gasoline make a big diffence?
I have a '81GS550T, great ride yeaterday.
A friend who is into performance bikes opined that hi test might be a better option due to the age of the bike. Any logic to this? Also any problems with the newer methanol blends?

[GQROD]

Most riders will tell you that it does not make a difference unless you are running high compression pistons, save the money and buy regular and throw some seafoam in the tank to keep things clean.

Ethanol seperates from gasoline, i have heard that running Marine Stabil prevents this, have not tried it yet only the regular stabil and have not had problems.

[supergrafx]

I'm interested in knowing this too. I have heard from a lot of members here that getting the best, 93 octane is a waste of money. I have also heard that U.S. gasoline is processed very crudely when compared to Europe/Australian/Asian standards. I've used 93 octane because of this, but maybe it is a waste. Someone will likely post a better answer.

[chuckycheese]

Search

Do a search for 'octane' here on the forum. You'll find enough reading material to last you all day.......

[uudfourty]

My GS runs on hopes and dreams.

[doctorgonzo]

The wacky logic of octane. "high" octane is MORE difficult to combust, so in a high compression engine you don't get pre-ignition. That means his logic is inverted. You are better off with lower octane gas on an older engine. I run 87, and avoid ethanol when possible.

[Nooner]

Thanks ChuckE, I searched octane and have enough to read all afternoon.

[jadesystem]

I use the cheapest regular unleaded gas......period !! I don't worry about octane rating as I've never had any issues with pre-ignition or sluggish performance related to gas.

Gas here is $2.19/gal. Gas supplies are plentiful and we are using less
of it. This recent price increase has no business logic other than political.

[first timer]

Like said, get 87 octane, these motors are low compression and anything more then that is a waste of money. Some modern bikes require higher octane due to engine design. But our gs's don't need it.

[Steve]

The wacky logic of octane. "high" octane is MORE difficult to combust, so in a high compression engine you don't get pre-ignition. That means his logic is inverted. You are better off with lower octane gas on an older engine. I run 87, and avoid ethanol when possible.

The overall, common logic is that "high-performance cars use high octane fuels, so it must make more power". BULL

High octane gasoline has fewer BTUs per gallon than 'regular' gasoline, so how can it have more power?

High-octane fuels came about as a Band-Aid. Engineers were finding that higher compression was making more power. However, higher compression raised the temperature of the compressed mix rather high and tended to ignite it before the spark plug. Adding octane in the form of tetra-ethyl lead reduced this tendancy, allowing the high-compression engine to make its power properly. Then they found that the higher-octane fuel burned slower, so they advanced the spark to get it to burn completely in time to maximize pressure on the piston to push it down. So, ... if you look at the whole picture, high-octane gas is a Band-Aid for the high compressio and advanced spark is a Band-Aid for the high-octane gas.

When you look at the total package of cylinder size, compression ratio and speed of the flame front, the engines in our GS bikes do not need any Band-Aids applied unless they have been re-worked to the point where they require them. Because high-octane fuel burns slower, there is a good chance that it will not burn completely in the time alloted and it may leave deposits on the head, valves and pistons. Eventually, these deposits will build up enough to cause problems of their own, but that's another chapter.

.

[supergrafx]

Because high-octane fuel burns slower, there is a good chance that it will not burn completely in the time alloted and it may leave deposits on the head, valves and pistons. Eventually, these deposits will build up enough to cause problems of their own, but that's another chapter.

.

My hypothesis was incorrect. Thanks Steve. I'll change to 87 octane instead of 93. I guess with this knowledge, it would seem that the carbs would gum up a lot faster using the high-octane fuels. But hearing that the engine's internals will more likely gum up as well, I will switch right away. The 93 is going in the lawn mower! Rather gum that up than my bike.

[chuckycheese]

Search engine

Thanks ChuckE, I searched octane and have enough to read all afternoon.

Cool! This subject hasn't been covered as extensively as some but it's definitely a favorite.

[SqDancerLynn1]

If you check the specs a lot of the current sportbikes are running 12 to one compression and are able to due to combustion designs and camshaft designes They need 92 octaine We only need 87

[duaneage]

My GS runs and idles better on 93 octane. I get some pinging on 87 that does not happen with 93. At 80 cents a tank it doesn't seem like a real waste of money to me. Since it's my bike I make that choice. As usual YMMV.

Alcohol is the real enemy. Try to find gas that is not E-10 or E-20 if you can.

[chuckycheese]

My GS runs and idles better on 93 octane. I get some pinging on 87 that does not happen with 93. At 80 cents a tank it doesn't seem like a real waste of money to me. Since it's my bike I make that choice. As usual YMMV.

Alcohol is the real enemy. Try to find gas that is not E-10 or E-20 if you can.

How would you know that? Can you tell by looking at something on the pump? Thanks!