I'm towing a 32 foot 5th wheel. Weighs about 10,500 fully loaded and ready to go. I'm towing with a 2004.5 LLY and am getting from 10 to 12 MPG under load. Not too bad but am looking to put a Bully Dog GT on it. I already have an S&B air intake and a Banks Monster exhaust. I'm new to this web site and have found it very informative and interesting.geo70brem