Knurled wrote: Well, let's see. My car would get 42mpg when running 92 octane, and about 36mpg on 87 octane. At 30,000 miles/year, that is about 714 gallons per year on 92, 833 gallons on 87. Premium would have to cost 16-17% more. The break even point if 87 is $2/gallon is premium at $2.33 - any more than that and it doesn't pay to use premium. Locally, there's a 15-cent jump between 87 and 89 and 89 and 92, so $2/gallon is about the break even part. When it's $3-3.15-3.30, it's cheaper to run premium. When it was 4.50-4.65-4.80, it really hurt to put $70 in fuel in the carbut I knew that 87 was DEFINITELY a false economy.
My car has gotten 46mpg on 87. 41-42 highway is easy. With my current car.. I'll invest the extra.
When I had a ranger, I put in 89 because I got 2.3 more MPG out of it and that was more than a 10% improvement.
Maybe I'm one of the crazy car people. I took a nice little economy car that ran just fine on 87 octane and modified it so that it now requires 93 octane.
Now I have 100% more power at the wheels but it still gets 33 mpg on the highway 
I have not put anything but 93 in my car in the 2 years I have had it.
On my old neon, it would run smoother on 93. I came across some numbers that the DOCH only hit 130HP with 87 compared to the advertised 150HP.
Either way I'm willing to pay an extra $8 a month. And if I get around to picking up the Mopar ECM, it will require premium.
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