Why am i not getting good MPG?

[strokin'_tatsch]

Originally Posted by longshot270

The K&N setup isn't exactly hurting you but to eliminate the CAI drone Bill has to go to a stock cam advance curve which isn't as good for performance. I would expect that the tow program would have modified cam curves for more performance while also having a richer fuel map to help on towing. With a CAI you usually have to use the richer tow program to keep from running a lean engine. The stock cam settings may be what are lowering mpg.

I also remember that you are running big tires. They are effecting the spark timing by effecting the RPMs.
As Bill said earlier when the RPM is low the engine load goes up resulting in the spark timing getting dropped to lower the chance of detonation. By lowering the timing you also lower both performance and efficiency. If the truck isn't regeared then your timing is getting thrown off because the RPM's aren't high enough. Also since you are slinging around more rubber the load goes even higher, dropping the spark timing even more.

Well said Colby.. so to put it very basic, you want the drone of the CAI gone so Bill pulls it down to stock cam settings, thus lowering power and MPG. the timing drops at lower RPMs in order to prevent detonation during certain loads. now you have larger tires thus compounding the effect of those loads and helping to create your worse MPG.

Try playing around with different RPM levels and calculate your MPG on paper, not computer.

And colby, you don't have jack that is messing with your aerodynamics. your bumper might weight 100lbs and your antenna ain't jack. heck my antennas that i used were much more than yours is, yet no difference in any mileage or anything and my truck already has the aerodynamics of a brick... haha. then again, it is a diesel, not a 4.6. LoL