if the manual of your car says to run premium, run premium. how many threads on the topic and misleading consumer reports-type articles do we need to the contrary? i cringed when a chicago news station ran an article about how premium gas is a giant conspiracy and the field reporters went station to station selling people on this bulls***.
turbo vehicles need higher octane gas. high compression engines need higher octane gas. engines running advanced timing need higher octane gas. if you don't use it and are supposed to use it, you're likely opening your self up to the following;
1 - poor combustion and detonation, resulting in engine damage
2 - engine knock, resulting in engine damage
3 - ECU seeing lean condition, misfire or knock and cutting back horsepower drastically
let's say you save 20 cents a gallon at the tank by using chummy 87 octane piss in the tank. so for a 12 gallon fillup you saved a whopping $2.40. if you fill up twice a month you just bought yourself a #1 at the golden arches. so by not using premium gas, for whatever reason, you've saved $57.60 a year or the equivalent of a dozen big mac meals per year. congratulations.
i hate to seem bitter about this but the whole premium VS regular thing from any standpoint is pretty ludicrous. the research is pretty easily obtainable as to why certain cars need premium gas. if saving an xbox game's worth of chump change per year is worth losing horsepower or damaging your car then thats pretty flawed logic if you ask me. the mp3 ecu is a nice compliment to pretty much every n/a mod out there and worth it i think. and if you are running an msp ECU (i thought pak's car was turboed as well, could be wrong) and pouring anything less than 91 in the tank you're not saving money, you're giving your engine a good reason to explode.