My 2004. 5, 6spd, 4x4 has about 9000 miles on it. Based on the posts I have read , it appears I'm getting about average hand calculated mpg at 14-15 mpg city and 15-16 mpg 75mph highway. It seems the reaction to TSB 18-037-04 varies quite a bit, so I have yet to take it in for service. I have been wondering if any of the companies that make the performance "boxes" have focused on increasing the MPG for the 600's. It seems to me that if they can optimize the motor for power they could also have a setting that optimizes for fuel economy. This would be a great selling point because it is very easy to justify the expense if you can get a payback from an improvement in mileage. This may be a a naive question because I have not looked into how these different "boxes" work.
Last edited: