Just thinking

[dirtynails]

So I live here in CO and my carb is jetted for that. I have family in Indiana and Kentucky. When I visit the truck doesn't run as well at the lower altitude. As far as I know, the only way to correct for that would be a rejetting which would not be practical for just one trip. So I was just now thinking about octane. Why wouldn't going to a higher octane act like richening up the mixture. Any ideas?

 

[Hogback Fabrication]

Because octane has nothing to do with your fuel mixture.

Octane numbers give you a reference to how well a given fuel will resist combustion (i.e. the higher the octane number, the harder it is to burn). Higher octane fuel doesn't have any more energy stored in it than lower octane fuel.

Engines make more power and get better mileage at higher compression ratios because thermodynamics states that the higher the compression ratio, the higher the efficiency.

You need higher octane to make sure that your motor doesn't spark knock (i.e. the fuel burns before TDC and without the help of a spark). Lower altitudes have more air pressure, which means more cylinder pressure, which means that they need higher octane fuel.