My 79 F100 2wd has a 78 Lincoln 460 in it (70K miles). When I did the swap (7 years ago) My father insisted on running 20w50 in this truck (said it was for longevity).. So did the new owner. I bought it back a few weeks ago. I'm going to do an oil change this weekend.
On the highway on an 80 degree day, oil pressure is around the "A" of normal (sorry, no numbered gauge, just the factory gauge). I can't say if the truck uses any oil, but it doesn't have any blue smoke and the bottom of the engine appears fairly clean with a slight film here and there, no massive leaks.
This is a 3 season truck, daily driving/tow once or twice a year/dragstrip once or twice a year.
What oil should I run? If I change to 15w/40 Rotella will I hurt anything? Should I run something thinner?
15W-40 would be my first choice, because it still has enough ZDDP for the older, flat-tappet cam engines. 10W-30 was probably the original spec, but they have taken out too much ZDDP, unless you can find 10W-30 Rotella, Delo, or Delvac locally, I cant.
My two local Wal-marts carry Shell Rotella-T 10w30 in quart containers, 4 and 5 gallon jugs, even bulk tubs, but I am not sure what those capacities are.
Unless you have a loose or sloppy engine, minor or major blow-by, I'd use this weight and grade of oil.
It will give your engine the protection it needs, plus it will allow the bottom end of your 460, the crank, rods, bearings ect. to run MUCh more efficiently, with less internal friction. Very important for towing.
You will actually make more power, as the engine does not have that thicker oil to overcome.
Cold startup and through the warm-up cycle, will be much better as well.
I say even 5w40 oil (synthetic diesel) will be a step in the right direction for you.
Last edited by Ed : 07-14-2007 at 01:05 AM.
Reason: misspelled word
The 15w40 is still awfully thick, for an engine that is still tight I take it? Overkill, but it's your $ that is being wasted needlessly.
Plus your oil pump is working much harder, needlessly, to pump that thick oil, when cold. I'll bet the oil is not even moving for a few seconds after your start-up.
This is why Ford never used 20w50, 15w40 as a factory fill, when that 460 was new.
