I keep a detailed log book and I have a drawer stuffed with reciepts, if I ever have to dig thru it for some I am sure I will find enough to satisfy them, since I buy so much clearance oil. Still I really do, do the maintence and probably overkill, I ussually use synthetic and it seldoms goes more than 3000 miles in 5 months, so it gets changed alot, I would be shocked if I ever have engine trouble and the oil changes get questioned. I have the Lifetime warranty with first car rental and 0 deducable, as long as they dont go out of bussiness. That said, My wifes car had a 40,000 mile service agreement with Lincoln when we bought it, I had the transmission serviced at 30,000 as scheduled by the dealer. It was still dark when I got it back, I called them and asked them about it, they assured me they changed it and it was documented and if a warranty issue arrised it would not be a problem, I had the service completed as specified. Well, when I changed the Transmission again at 60,000, the little yellow assembly plug fell out in the pan, proof they never did the service, just documented it. That dealership went under about a year ago, I am sure they are not the only ones.