hello all....i have a si coupe.....how much of a difference in performance is there if i use plus fuel or premium?

 

no real performance gain... octane rating is just the fuels resistance to detonation.

 

+1
[align=left] [/align]

 

If the manual suggests running 91 or better ocatane than why not spend the extra 5 cents a gallon and treat the car right. Around me plus is 89, and premium is 93, go figure.

 

For real. It works out to be about $2 extra for the primo where I'm at in Cali, so I figure why not? My car requires 87, but I drop 91 all day in it. It's a blind investment. I can't really test the difference between the two, but for the extra say $5 a month I'm willing to take the chance on getting some benefits with no chance of negative impact.

 

Unless the car has a knock sensor, which can allow the ECU to tune itself for higher performance given higher octane, it's a pure waste of money putting in a higher octane than required by the manual.

 

He says that he has an Si, they require a minimum of 91 octane, some places don't have 91 octane on the pump, either 89 or 93 so I like to spend the extra 5 cents a gallon for the 93 octane, it can't hurt where as 89 may have negative effects on the engine.

 

5 cents a gallon!!!!!!!!!!!! i have to pay an extra 20 cents a gallon for premium. damn... where do you guys live at. i am in az

 

There's no big tank of plus ata gasstation, only regular and premium. When you use the "plus" hose, the pump is mixing the two to get an intermediate octane. For example if they have 87, 89, and 93, the 89 is a 2:1 mixture of 87 and 93. The interesting thing is the price of plus is almost always a ripofffor what it is. You can get exactly the same product and pay lessby filling your tank partway with premium and then the rest with regular.

 

^ wow.. never knew that.. I guess you learn something new every day

and I just tested your logic on the whole saving money thing. It doesn't make a difference:

For example, let's use "1" as the price for regular unleaded fuel. Using that price, a 14 gallon tank-full of regulargas would be$14. Now, since plus gas is $.10 more per gallon, the price of plus would be "1.1" Using that, the price of a 14 gallon tank-full of gas would be $15.40. Then, premium gas is a whopping $.20 more than regular. Thus, the price ofpremium would be "1.2". This means that a 14-gallon refill with premium is $16.80. Now let's test your theory; half a tank (7 gallons) of regular is, using our "price", $7. Now, let's add the 7 gallons of premium: $8.40. Now, add that together; it's $15.40, the same price as plus gas.

(I'm not trying to be an *** or anything; I just got bored and decided to test your logic. I figured I might as well show everyone the results, ya know?)