Originally Posted by aakrusen
I think it will improve your MPG because the only the rear wheels are putting resistance on the system. Look at it like a 4wd truck. Put the truck in 4wd and your mileage goes down. Put it back in 2wd and the mileage gets better. Now the increase in mileage might not be spectacular, it should be an improvement.
Fueleconomy dot gov says that the 335xi gets 17 city and 25 highway. For the 335i it says 18 city and 26 highway.
Yeah, but you are comparing an i to an xi. The xi has a front diff that stays engaged. All you're doing here with the fuse is disabling the front output. Unless you have disengaging hubs, which the xi does not have, you're still going to be spinning the front drive components and you will still have the same amount of drag. If you read through the thread, people have said that the front output of the transfer case disengages at highway speeds anyway.
So, I predict no improvements in mpg. Change out the intake, that'll give you better mpg.