Had my 07 4.6 f150 at dealership about 4000 miles
ago. Told me #5 cylinder has lost compression.
Truck runs good no loss of power but idles just a
little rough. Has'nt gotten any worse.Would using a
heaver oil + engine restore help? Has just under
It can't hurt to try but nothing I know of will fix lost compression other than an engine rebuild. I would not use anything heavier than 10W- 40 as your engine is designed for 5W-20 oil.