I was reading somewhere that if you run a higher octane that what is stated in your manual that it could actually cause more engine build up and end up hurting the car. Does anyone know if this is actually true?

 

It won't run optimally so you will be wasting money, but it shouldn't cause things to build up more...

 

So really running a higher octane does nothing other than waste your money?

 

Yes, unless the PCM has been programmed for running higher octane.

 

And/or engine modifications which require the higher octane.

 

I always use 93 in my 4.3 and got around 300 miles per tank, one week I was running low on cash and filled up on 87 i noticed i only got 200 miles on that tank and it ran like poop.

 

That is because of the massive amount of carbon build up in your cylinder heads...lol

For those that don't know, a higher octane number actually means a slower burning fuel. This is why high compression engines (read as performance) require higher octane petrol to prevent detonation, the fuel/air mixture "exploding" due to the increase of of pressure rather than being ignited by the spark plug. This can and will cause damage to an engine.

I've never heard of any ill effects of using a higher octane fuel in a vehicle that does not require it, though some state they get better mileage. I tend to trust the vehicle manufacturer as they have spent a few more dollars on R&D than I can ever hope to make in my life time.

 

If more people realized that they might have fewer issues.

 

I dont know how you get 300 miles to a tank im lucky if i hit 200 or more and that is babyn it to! I usually run 89 but once in a while i run 91 and it runs way better but i can only do that once in a while. if i run 91 twice it runs like ****. so i go back to 89 and it runs great till it starts getting slugish and i run 91 again.

 

I was getting 340 plus miles per tank on my Blazer, whiched avereaged out to be 17 mpg. While pulling my engine out to put into my S10 Baja I noticed my sparkplugs were fouled with carbon. I had been running a 180 t- stat so now i switched to a 195 with new plugs and o2 sensor and fuel filter. Not related to the ignition but I also flushed the tranny replaced the filter.

My first tank mostly freeway lasted 380 miles for 19 mpg, and i'm still working on the current tank of gas with 5 or so gallons remaining i'm guessing about 17 mpg right now. I've always ran 89 octane with some seafoam or marvel occasionally added to the fuel.