We have a 2004 4.7L Tundra 4X4 Limited Access Cab with 43,500 miles. Love the truck! In the past few months I have noticed a puff of blue smoke when starting after letting the truck sit for a day or two. We had a '92 Camry which did the same thing at 55,000 and it had to have its valve stem seals replaced. Am concerned that the same thing is happening to the Tundra. I have always used Mobil 1, 5W-30 in the truck (changed every 5000 miles) and was wondering if maybe the oil is too thin when cold and leaking past the seals. Has anyone else experienced this?