I have an auto B6 S4 and it does fine with gas mileage, just as mentioned above. Although I do get into the mid-20's on the highway which is nice. And as previously stated, if you want the V8 engine and the power, you will have to sacrifice a bit on the gas mileage.

Mine is up for sale. Here are some details:

2004 Audi S4 which is Audi Certified Pre-Owned until April 2010 or 100,000 miles. Dolphin Gray exterior with Light Silver Recaro racing seats. This car is equipped with:

- 4.2L V8 engine cranking out 340 horsepower
- Tiptronic transmission
- Quattro AWD drivetrain
- Premium Package (which includes folding outside mirrors, homelink, sunroof, light sensor package, driver memory seat and auto-dimming rear view mirror)
- Front Heated Seats
- XM Sateliite Radio
- 4 spoke comfort multi-function steering wheel
- New Toyo Proxies 4 tires with only 1,000 miles on them

The car has 45,000 miles currently. This car has been well maintained, always hand-washed, never had any issues with the car and it runs great. Only reason I am selling it is because we have a baby now and I need to get something larger.

Please feel free to contact me at andres4567@verizon.net with for more information. Thanks.

 

With the B6s the mods are quite limited versus the B5s as previously stated. Really the only things worth doing are a chip reprogram and an exhaust job - at best they'll net you ~40 HP at the crank and cost $1000-1500. You can do downpipes, etc., but you'll get diminishing returns on your investment. Of course, there always the $20,000 MGM supercharger option, if your stinking rich.

 

By the way, you can get 2 car-seats in the back and still have room for someone to squeeze in the middle. :-)

Just sayin'...