20 weight or 30 weight?

[semaj281]

1. What kind of vehicle you have
2008 Ford Mustang GT
2. What your owner's manual says -- not just viscosity, but certifications (look for acronyms like API SM, ILSAC GF-4, etc.) and change intervals as well
Can't remember offhand but I believe it calls for API SM with the Ford WSS specification.
3. Where you live
Georgia. Temps range between 10 degrees F and 100F.
4. How you drive (easy? hard? fast? slow?)
Worst case scenario is 10 consecutive runs at the 1/4 mile strip on a 90 degree day. This is done maybe 3x a year. Any other time I shift at 2500rpm. Highway cruise rpm is 2000. About 80% is highway mileage.
5. What your daily drive is like (short trips? long trips? city? highway?)
I commute 30 miles one way. If there's local driving involved, the engine is warm by the time it's shut down. It never idles for more than 2 minutes.
6. Whether your car has any known problems
None, besides some oil consumption of 1 quart every 5k. But I believe the engine's still breaking in. It's got 7800 miles now.

Thanks a bunch everyone. Aside from warranty reasons, would I benefit from the 20 weight?

 

[tomcat27]

I presume you have the 4.6 with the WSSxxxx930 spec and not the 5.4 with the WSSxxxx931 spec. If so, the book calls for 5W-20; but me (not being a Ford engineer) would be tempted to run 5w30; at least in your locale. up here I would run the 20.

supposedly ford has run that engine a gazillion miles on 20 - but I dont believe that the factory bearings specs changed when they changed their recommendation from 30 to 20.

 

[HTSS_TR]

Since your car is still under warranty, I would use the recommended oil weight as stated in the owner manual. After warranty then I would stay with xW30 because of the 1/4 mile runs.

 

[semaj281]

Originally Posted By: tomcat27
I presume you have the 4.6 with the WSSxxxx930 spec and not the 5.4 with the WSSxxxx931 spec. If so, the book calls for 5W-20; but me (not being a Ford engineer) would be tempted to run 5w30; at least in your locale. up here I would run the 20.

supposedly ford has run that engine a gazillion miles on 20 - but I dont believe that the factory bearings specs changed when they changed their recommendation from 30 to 20.

Yessir. It's the 4.6L 3v with variable cam timing.
And you're also right about the 5w-20 recommendation but currently running 5w30 regardless. I'm just wondering if that was a good decision.

 

[panthermike]

5w30 certainly won't hurt anything. I've been toying with the idea of running 2qts 5w20/2qts 5w30 in my Ranger in the summers here(calls for 5w20). Only issue is warranty, but not a problem because I bought some cases of 5w20. If I had a warranty issue, it's on paper...... doesn't mean it's in the truck though

 

[tomcat27]

in the rare event that your motor pukes, drain out the 30 and put in the 20. some shops run oil analysis when motors puke. A friend of mine who runs a motor rebuilding shop does that on warranty claims. I know on one occassion he warrantied a buick 3.8 with only 35-40k on the rebuild - although he shouldn't have. he drained out 7 quarts of oil that was very heavily diluted with gas. still rebuilt the motor - and only gave the customer a mild scolding. good guy - Lanny - he's rebuilt 2 engines for me.

 

[Audi Junkie]

10w-30

 

[semaj281]

Originally Posted By: tomcat27
he drained out 7 quarts of oil that was very heavily diluted with gas.

Is this an undoubted sign of abuse?

But as for the OP, I think I answered my own question. Because I remembered reading about the CAFE reasoning.

 

[jorton]

"None, besides some oil consumption of 1 quart every 5k. But I believe the engine's still breaking in. It's got 7800 miles now."

Agreed

"Aside from warranty reasons, would I benefit from the 20 weight?"

I think so. There is one clearance that's closer in modern engines. Piston-cylinder wall clearance. The engine in your GT is a passenger car engine. Racing engines need thicker oil.

 

[Hitzy]

Redline 5w20 if you are going to run a 5w20.

 

[PT1]

If you want a thin 5w30 try Castrol Edge. It is almost a 5w20.

 

[Alex38]

Originally Posted By: PT1
If you want a thin 5w30 try Castrol Edge. It is almost a 5w20.


+1 If I were to run a 5w20, it'd definitely be a synthetic. Personally, I'd go 5w30 though, especially with where you live and with the 1/4 mile runs. I've been putting 5w30 (Mostly GTX) in my Mom's 2002 GT since new. Still runs like a top, and no consumption.