I’ve come to the conclusion that Mobil 1 Extended Performance oil, or possible the newer formula (last 10 years or such) has been changed so that it breaks down fairly quickly and the result is high oil consumption. I assume it becomes thinner as it gets old.
I changed someone’s oil with STP 5W20 full synthetic and after about 250 to 300 hours the dipstick was down to middle. Then I used mostly Mobil 1 EP 5W20 and after about 340 hours when I changed it again it was down half way below the bottom mark on the dipstick.
I read on another forum that someone with a Toyota truck changes his oil after about 8000 miles with Mobil 1 EP, since at that point he notices a reduction in fuel economy. If you’re waiting for a noticeable change in fuel economy to change your oil that can’t be good. (Edit: this was previously in the paragraph above by mistake): The oil is probably getting too thin and messing up the variable valve timing.
Their claim of 15,000 or 20,000 miles of protection for Mobil 1 Extended Performance must be based on the oil burning off fairly rapidly after the first 5000 miles and then you have to add a quart every 2000 miles or so after that. So you would have to add another 5 quarts to get to 15,000 miles and it would still be a quart low at that point due to the normal consumption during the first 5000 miles. So you are using about the same amount of oil as if you had just changed it at 7,500.
Has anyone else noticed this about Mobil 1 Extended Performance oil that was purchased in the last 5 years?