I've actually been dealing with this problem since I bought the truck in 2014 at 125k. I should have known better when the car was 1 quart low during the test drive. Anyway, I was unsure of the history of the truck and consistently have been using 5w30 High Mileage Mobile 1 since I bought it. The truck has been burning a quart every 1000-1500 miles which is driving me crazy! Sometimes I forget to check it and it is close to 1.5 quarts low! Never had any oil lights and it always starts up (have been dealing with a loud timing chain rattle since purchase though). For the first time since purchase, I switched to 10w30 Mobile 1 High Mileage when I changed the oil today; I'm beginning to wonder if I should give up with the Mobil 1 synthetic and go with conventional. I've been trying to be patient, but there is obviously some issue going on with my truck; I feel like I have to check the oil every time I drive it! Any ideas? Thank you!