The premium does have the good stuff but some cars can't use it due to Direct ignition. Some people that do need it for turbo, or any kind of forced induction just advance the timing at the dealer(Direct Ignition) or if they have a distributor they advance their timing.
Some cars with the right timing and premium gain some hp. I've even heard of altimas getting 6 more hp with premium and advanced timing.
I get my best mileage with 87. Also using premium for a car that was designed for 87 will get a carbon build up. My stock compression should be 178 in all 4 cylenders. I'm at 190 in all 4. This is what happens when you use premium when you're suppose to use regular.
It is possible to gain some HP from premium fuel in a car that only requires 87, because premium fuel does contain more power in the same amount of fuel as 87. It takes longer for the fuel to burn, this is why you need to advance the timing to get a possitive effect, otherwise its a total waste. This is why you get better mileage with 87, you've effectively advancing the timing (as compared to running 91). So unless you've changed the ignition timing, run the recommend fuel rating, otherwise you're tossing money away.
Also, using premium fuel should have NO effect on your compression readings.
my gas purchase is based on credit card rewards. my favorite is shell, so that is what i use most. prices are no issue in my area. they all are very competitive except for sam's and race track, and i won't buy either of those!
incidently, i tested most of the gas in my area, and have concluded that shell gives the best value(mpg yield). sadly, chevron, i thought was better, but both stations near me closed.
I am with dax on this one. I just go where ever. I the price at one place is really high i will go to another gas station.
same here, convinience to get into the station (like an easy right turn to get in and a right turn to get out) is a major key. price somewhat is. in my hometown area certian stations are routenely higher than others while some are the cheapest. i try to go to the cheapest one but not a big deal if im not heading that way