robs

Thinner oil = less friction = fraction more miles / gallon

Talked to one of the primary engineers that developed the 5w-20. They developed the oil before they developed the application (i.e. Ford spec'ed as afterthought).

I asked him if HE would use it... said... "Only in the winter".

mygt500

no worries and just switch back for the next one!

S281 E

I wouldn't worry about it. Not the first time someone made the mistake and won't be tthe last.

cummins cowboy

a 20w oil is way too thin, you probably hear the valve train being louder with it. good ole 10-40 IMO is the best all around oil imo

Riptide

I've never read or heard of a single engine failure due to using a 20 viscosity oil.

It's nothing to be concerned about.

sailing220

I've only ever used 5W-30 in my Stang. Your car will live.

Norm Peterson

A guy on another forum who was much closer to some development with modular engines than either of us will ever be won't run the 5W-20 in them. FWIW, he's into AIX racing and is an engineer at a slightly higher level of racing, so it's possible that his recommendation might be a little on the conservative side for mild to maybe moderate street driving.


OP - you should be fine. The cam phasers might behave a little differently with respect to rpm and response but I doubt that much else would change.


Norm

Riptide

Scott Whitehead. I've heard this discussed a million times over. There have been other Ford engineers who have said that it's fine and not to worry. Some guy on bobistheoilguy knew one of them.

20 isn't going to hurt anything for even moderately hard usage. Running a supercharged car on a road course and beating the crap out of it? Might not hurt to switch to a 30.

mcburns36

I run 10 w 30. No problem

cummins cowboy

why not 10-40, you have light oil when its cold and heavier if you need it when its hot, best of both worlds

in response to another comment never heard of an engine failure running 10-40