Originally Posted by bpas328xi
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.
I don't know what highway speeds you are going at, but it turns RWD at 100mph, not highway speeds.
I think there will be an increase in gas mileage, however, it will not be noticeable. It will be very slight. You will see the increase because the clutch transferring power to the front will be open, i.e. no friction losses, but you still have the weight from the AWD system. It might be somewhere between an i and xi, leaning a little more towards the xi I would think.
Update on my status:
I am taking tons of data at the moment and trying to reverse engineer some things. I can see the light at the end of the tunnel. This is really getting fun