gas, which one is bestw Options

[rodriguez046]

Whats the best fuel to use on our cars?

[Special_Edy]

In short octane is the fuels resistance to burning. Higher octane requires more energy to combust, so its less likely to predetonate. The higher the octane rating the less joules of energy the fuel contains. Diesel fuel for example is 30 something octane off the top of my head yet contains TWICE the energy per gallon as 87 unleaded. Thats why diesels are so efficient.

The flip side of this is that higher octane fuel allows you to increase the compression ratio and ignition timing advance; both of which increase the efficiency and power output of the engine. The compression is fixed so unless you plan on rebuilding your engine this aspect doesnt do you much good. The spark timing will automatically advance itself on EFI engines like ours to try to make use of the higher octane, but the benefits are negligible compared to the increased price per gallon and our low compression ratio.

Remember that sign that says "gas may contain up to 10% ethanol"? Well ethanol is something like 120 octane. So how do you think they make 93/91 octane gas? They add ethanol.
There are usually two unleaded tanks in the ground and maybe a third tank for diesel buried under the gas station. So mid grade gas, 89 octane, is simply a mix of the regular and premium gas from those two tanks underground.


As for chevron, I like chevron. Shell is the only fuel I put into my vehicles but I will use chevron if I have to and BP in a pinch. I dont use RaceTrack, QuickTrip or any other bargain gas because from personal experience it makes my carbureted vehicles run like crap. The EFI may not run any different on the cheap gas but its clear to me that there is something superior about Shell and Chevron