I have a 1998 T100, 3.4L V6, 4WD, automatic, stock, with 265/70-16 Dunlop tires. I used it on a business trip last week and get reimbursed for mileage, so I kept an accurate record. I filled it up and drove a round trip of 297 highway miles on I-70 in Kansas. I went 75 mph with the cruise control and air conditioner on. I filled up as soon as I returned home, and got 18.7 mpg. My gas tank holds 24 gallons.