With stock 3.55's I was happy.
With FRPP 4.10's I am even happier.

 

Go 5:56's cuz dats what I got an they reel gud.

 

Blue Star had 4:10s' and didn't like them on the interstate. It isn't for everyone. But since I race more from the red light then all out top speed they are perfert for me. But also remember they wind out faster and will give you a jump on the interstate as well.

 

I have an automatic with 3.73 gears. I notice you are an auto as well. I dont think there was ever an option for 3.55 gears in an automatic. My mileage improved slightly around town. i get 19.2 MPG with all city driving. If I reset average fuel economy and drive on the interstate,I can get around 25 to 26 MPG (babying car of course). You will turning 2000 rpm at 60 mph with 3.73. I you go with 4.10 you will be turning around 2300 rpm at 60 and around 2700 rpm at 70. (tire diameter will also affect rpm). I have the 18 inch wheels and tires from factory. If you have 17 inch tires from factory your rpm may vary a little from mine. You will notice an increase in the seat of your pants feel with 3.73. It is a good all around gear. If you are wanting the most seat of the pants feel, 4.10 would probably give you more. If you want a good all around gear 3.73 may be the gear for you. If you ever plan to supercharge go 3.73. With the mods in my sig, I can stomp the car from a dead stop and spin half way through first gear and grab second very hard and chirp third. I hope this was helpful in your decision. Overall I am happy with 3.73 gears.

 

I thought he was M5 based on the Hurst Shifter?
In my opinion..... 3.55 to 3.73 isnt enough to bother with.
Going from 3.31 to 3.73 is pretty good difference.

Personal opinion on a M5 at 75 mph:
3.31 = 29 mpg
3.55 = 28 mpg
3.73 = 27 mpg
3.90 = 26 mpg
4.10 = 25 mpg
4.30 = 24 mpg

The 3.31, 3.55, and 4.10 mpg are based on actual cars. The others are educated guesses.

 

Yep, its a manual...5spd...I'm thinking of going the 3.90 route...of course now it has stock 3.55s...I think the 3.90s with a CAI, tune, the alxe bakcs and shifter it should be quite fast off the line... I'm not a racer I just like to tinker and only need to go fast from time to time in a straight line....yea know....Also doing the 3d carbon grill with tri pony and GT500 spolier this weekend....That will be harder than the gears because I have to stripe that damn spoiler to match my car...(performance white with ford blue 10" stripes....) Its looking pretty good though so far...I had no idea this would be such a money pit whenI bought it...stinking internet is evil because it has put all these ideas in my head...

 

If we were playing Liar's Poker , and you called out those numbers, I'd challenge you. You're saying 75 mph which with 4.10's is about 2900 rpm's......and you get how many miles to the gallon.

 

22-25 on the highway is pretty close with 4.10's