what gas is better for insight?

[Cobb]

I can make mines do that. Just after the cold engine light goes out, try giving light acceleration at 25 mph with windows open. You can hear it and if you got a scanguage2 you can see it retard the timing to like -20 degrees or some low number like that. With mid grade I have seen as much at 36 degrees+ of timing.

[R-510]

People often think that higher octane fuel means more power. This is understandable because the cars that require high octane fuel usually have high horsepower and/or high compression motors.

But in fact, just the opposite is true. Gasoline is a mixture of many hydrocarbon molecules, and in general, the longer-chain molecules burn slower, releasing their energy slower. Think diesel vs natural gas, which one burns faster and hotter? The main reason high-compression engines require high-octane fuel is so that it does not self-ignite, causing knocking and pinging. They would use the lower octane fuel if it did not self-ignite.

Most of the gasoline molecules have between 4 and 7 carbon molecules. Octane has 8 carbons, and hence burns slower, releasing its energy slower.

The higher octane fuels are designed for larger engines to slow down the burn of the relatively large amount of gas being burned all at once, and to prevent pre-ignition or self-ignition.

Putting high octane fuel in a car not designed for it will result in less power output.

Something the oil companies don't brag about, since they make much more profit off of the higher octane fuels.

R-510

[dieselnine]

Thanks for the super explanation of the makeup of gasoline. I had kind of been wondering if I should try the mid-grade gas, but won't after reading your post.

[circa1986]

Originally Posted by R-510

People often think that higher octane fuel means more power. This is understandable because the cars that require high octane fuel usually have high horsepower and/or high compression motors.

But in fact, just the opposite is true. Gasoline is a mixture of many hydrocarbon molecules, and in general, the longer-chain molecules burn slower, releasing their energy slower. Think diesel vs natural gas, which one burns faster and hotter? The main reason high-compression engines require high-octane fuel is so that it does not self-ignite, causing knocking and pinging. They would use the lower octane fuel if it did not self-ignite.

Most of the gasoline molecules have between 4 and 7 carbon molecules. Octane has 8 carbons, and hence burns slower, releasing its energy slower.

The higher octane fuels are designed for larger engines to slow down the burn of the relatively large amount of gas being burned all at once, and to prevent pre-ignition or self-ignition.

Putting high octane fuel in a car not designed for it will result in less power output.

Something the oil companies don't brag about, since they make much more profit off of the higher octane fuels.

R-510

While this may be technically true, in reality, if you put premium in a car that is not designed for it, you will get exactly the same power output as you would if you put regular gasoline in it.

Ironically, my Insight knocks on regular gas occasionally. At least it did when I first got it!

[livfreely]

pure-gas.org to find out where the best gas is near you. Hopefully a station will be near by. Ethanol-free gas stations in the U.S. and Canada

[webskipper]

Excellant topic.

Owners manual states 87 octane.

Service manual states 91 octane.

I have used 89 octane for the life of the car except When driving through Canada then its 91-92 or whatever is above 87.

I did use something mostly containing ethanol or was actually E85 when traveling through Texas. Was not a more than 7 gallons and then refilled with 91 octane every personal pit stop so I could sleep soundly that night.

Killed my mpg.