I'm doing some experiments on using cooking oil as engine oil, partly for green living brainstorming and "backup plan" experiments. I'm using a number of well worn (read "donated and thrift store finds") lawn mowers, and while I have found relatively few issues, though I still wouldn't use it in my truck unless I was in a world of hurt. They seem to overwinter fine with the veggie fat in it, which supprised me a little, but still had a bad engine turn rancid after 2 years, much longer than expected. I would really like to track down an oil testing kit, haven't seen any in awhile. Anyone else have any thoughts?