TOOT

I've definatly kept a close eye on the dip stick[sm=nerd.gif]

oxfordgt

If you run heavier weight oil you can destroy your engine. The 4.6 has very tight tolerances and to thick of oil can not get where its supposed to.

TOOT

Yes i made that mistake by adding 1/2 quart of 10/30 RP.[][:@] The car sounded like it had a heavy cam for a min. until the oil heated up[&:]

cliffyk

Print out the service limits for a 4.6L SOHC and any other engine made since 1980 and show me where the "tighter tolerances" are--that's a line you've been fed to justify the thin oil, along withthe "return from the heads" stuff. [/align][/align]It simply isn't so, I don't care how many times it's repeated--5W-20 is too damned thin for optimal engine life, especially here in Florida when a good portion of your driving involves 250-400 miles sprints on the interstates. [/align][/align]I guarantee those guys doing the 500 mile sprints down the street from here don't run 5W-20 oil...[/align]

gjscott

Mobil 1 is synthetic.

4.698GT

Mobil's 7500 mile is a synthetic blend if you are still looking for it.

TOOT

The manager said that 5w-20 was too thin, offering a coating for the engine's internals but little else.

Chopper

Try looking at this website,it's got a ton of info about different lubes.
http://www.bobistheoilguy.com/

Tighter bearing clearances or not,our engines DO have sintered iron oil pump gears that don't need any more stress from heavier oil to cause them to break under high RPM operation.

BuzzCut

Just drive it. 1 quart isn't squat. It is highly unlikely you have a ring problem. I would lean towards valve stem seals before that. You can also check your PCV and see if it id sucking oil into it. MY 97 GMC would use oil like that and I did some research and found a new style PCV valve to use and my trouble went away.