I have a 2003 Honda Accord v6 and I use the expensive grade gas because I heard that the high grade makes your engine run better and the cheap stuff gunks it up. Is this true?

 

No. Your engine was meant to run on 87 octane. Putting in anything higher than 87 can damage the engine, not help it.

 

x2. However, with this being said, do avoid shady gas stations whose prices are much lower than others. More times then not, their gas might be mixed with water like some stations in Miami have been reported.

 

High octane makes your car faster, because your wallet will be lighter.
Seriously, I don't think it'll do any real damage, but it certainly will not help. Probably get less MPG, but so little difference its hard to measure.

 

I agree, use 87 octane. The only time you need top use higher octane gas is if the engine is pinging (typically on some older models).

Higher octane gas actually burns slower than lower octane.

 

I just realized he has a 2003 V6. I seem to remember a study done on that engine where higher octane actually did increase horsepower on that engine because of the way it was designed.....

 

It does seem that when I use the higher octane gas it lasts longer. I am not that worried about a lot of horsepower, my wife drives the car to work. We don't take it to the track or anything.

 

If anything, higher octane gas would get WORSE MPG, not better.