We purchased our 2008 GMC, see sig, in December with 102,000 miles and love the truck. Check the transmission cooler lines just under the front air dam. The lines are known to leak, mine were and I had the dealer replace them prior to purchase. Truck pulls great and look forward many years of service. We paid $29,000 for ours. Tank should be 38 gallons, ours had a 100 gallon transfer flow already installed. Averaging 15.6 MPG bobtail in mixed driving and 10.2 to 11 MPG pulling our 12600 lb fiver. You will love this truck. Good luck.