I, too, take the position that a decent 5W-30 or 10W-30 oil (presuming either or both would be considered an appropriate choice for the prevailing seasonal temperatures in your area in past years) would not harm your new Ford engine. However, the 5W-20 oils are showing good wear numbers and resistance to shear on the oil analysis reports trickling in, so they're apparently not a bad choice, either. Ford's been making engines longer than Carter's been making little pooper pills and I would venture that their engines are statistically as trouble free, overall, as anyone's. But, the occasional defective one does show up. So, the real problem, if I might use a baseball analogy, is being called "out" on a controversial warranty "pitch" in the event of engine mechanical trouble if the dealer or Ford pulls an oil sample and has it analyzed. You need to understand that the "opposing team", Ford and the dealer, are also the "umpire staff". I readily concede the point that it's YOUR car, and Ford's decision to require 5W-20 oil is probably arbitrary and based solely on milking a few tenths of a percent more in the CAFE numbers. But, until your powertrain warranty expires, it might be prudent to evaluate carefully the potential personal financial impact of using a non-specified engine oil.
[ March 09, 2003, 09:55 PM: Message edited by: Ray H ]