Gas Mileage

dodge guy wrote:

Lynnmor wrote:

azdryheat wrote:
Octane has nothing to do with mileage.

It sure does if the knock sensor detects knock and the ignition timing is adjusted to compensate.

Yes it does. I proved it on my V-10 Excursion. Used to run 87 and power and mileage were down horribly! Switched to 93 and it improved. The. I got a tune from 5 star for 89 octane and it was better. My truck was over maintained so it was running 100%. You may not see a lot more mileage but you should feel the performance.

OP. Only you can decide. Run 2 tanks while towing and see for yourself.

Actually you are all correct

If when new, your vehicle manufacturer states that regular gas is all that is required then you will not get any benefit from running premium gas. Your engine is already running as efficient as it can.

If your engine is very high mileage and has substantial carbon build up in the combustion chamber, it may slightly increase compression to the point of pinging under load. In that case you would get a benefit from premium fuel. The higher octane will only assure a more efficient fuel burn, preventing the pre ignition ping as some call it. When the knock sensor detects poor fuel burn/pinging the computer will adjust the timing in an effort to reduce the harmful detonation. This will reduce performance and mileage. So in this case yes it will help you get back to where it used to be before the carbon build up happened. But still no gain from when the engine had no carbon build up.

The only thing that will improve power is compression. Performance engines manufactured with higher compression pistons or crank strokes will require a higher octane fuel. Those cars will recommend to only use premium fuel.

So, too low of octane can cause detonation and reduce power and mileage, but once the balance of octane is achieved to eliminate preignition, it has reached it's ultimate goal. There's nothing left for it to do.