I use 5/20 motorcraft synthetic blend with the 820s filter in my 02 Lightning and my 01 Expy. I change the oil in both of them at 3000. The L has roughly 4400 miles on it with no problems. No knocks or slap. The expy has around 21500 on it and has just developed the knocking noise when you first start it up. After it warms up the knock is greatly reduced. Is it the oil? I don't think so. I just think Ford has a serous problem with these engines. BTW, the Expy has the 4.6.

With all the horror stories I hear on this forum about the Ford rebuilt engines I am hesitant to have it fixed. On the other hand I paid a lot of money for that truck and I think Ford should have to fix it or buy it back. What would you do if in my place?

Oh, as a side note my 91 F150 has around 122000 and runs like a clock and has never had anything done other than routine maintenance and brake job.

 

If you feel that anything is wrong when the vehicle is under warranty take it in--it doesnt hurt you at all and you should even be able to get a loaner vehicle if you are old enough.

One other thing, the 4.6 aren't the engine people are having rebuilt and having problems with it is the 5.4 with the piston slap and such.