I've tried 87, 89, and 93 with multiple fill-ups of each. I found that they all "feel" the same, I didn't notice any performance differences between them. What I did find was that with 87, I got some knocking when initially starting the car, but not after that. I didn't particularly care for that so I won't be using 87 at all anymore. What is interesting, though, is the mileage differences. I consistently get in the 17's using 93, 18's using 87...and 19's for 89. I have no idea why, but it seems 89 is the mpg sweet spot, at least for mine (it's an A4).