5W20 will reach the heads/cams faster on cold start-ups. Also, the clearances in the engine are designed for the recommended oil.
They recommend 5W20 for a reason.

My 88 5.0 Mustang ha 163K on it and still holds 22psi oil pressure hot @ idle and about 45lbs @ 2000rpm. These are hard miles with lots of NOS used back in the day!!! It still runs like a scalded dog and I have always used the oil recommended for it. 10w40.

 

guess my truck is screwed then, i have used 10w30 mobil 1 since about 10K miles...

i live in south texas where it is warm in the winter and hotter than hell in the summer. i have always been told the 10-30 holds up better in hot conditions...

 

South Texas for me, too. South East Texas to be exact, on the Gulf Coast.

5W30 is available to me through my job. They give me an oil change a month for my work truck, and I don't use one every month. I change the oil every 5,000 miles on my work truck, and I drive about 3,500-4,000 miles a month. That makes one available for our Ram every four months or so.

I agree the $24 for the 5W20 from WalMart is no big deal (unless my wife needed some "retail therapy" this week!), but if it really makes no difference other than the last 0.2mpg required to make 18mpg on the EPA test, then I won't bother getting the 5W20, and use the 5W30 instead.

 

idk dude i found 5w20 no problems just went to autozone and got the mobil 1 full synthetic 5w20 and threw it in there. no problems whatsoever. why chance it tho just run what they say.

 

Any updates with new information?

 

Nope, obviously with Fay deciding to camp out over my head for the better part of three days, golf was cancelled last night. Hell, with 20+ inches, it may be cancelled next week. I've got the GM's email address, not the Service mgrs., but maybe I'll drop the GM an email and see...

 

dreman,
Sorry it took so long to get an answer on this one. Golf was canceled two weeks ago due to fay and last week because parts of the course were still very wet.
Played with the guys yesterday and according to the service mgr. 5w-30 is fine. He says he's not been "officially" told this, but believes the 5w-20 specs is mostly because the MDS Hemi's require it, and by recommending the same it saves cost on buying the 5w-20 in more bulk for both Chrysler and the dealers. He said if both were available he'd personally use the 5w-20 because it's both recommended and being thinner, yields better fuel economy (however very slight). Although, being in Fla, he'd actually recommend the 5w-30 would be a good idea for hot climates. In norther climates though, he likes the idea of the 5w-20 in the winter, especially in vehicles with cooler than stock thermostats...

 

So for us in Southeast Texas, 5w30 should be fine. Thanks!

 

Ford has used 5W20 in their OHC engines since 2000. It gets oil to the top of the engine where the cams and all are faster at start-up. Plus the clearances are tighter these days.
Why vary from what the engineers recommend??

 

Hell, I'm actually varying from specs, but the other way. Book says 5w30 for my '04, and everyone knows that they want 5w20 in the MDS Hemi, but the '05's (identical to the '04s) manual calls for 5w20 as well. Based on that and more importantly, the fact that I'm running a 180* thermostat, so the engine temp stays cooler, I run 5w20 Royal Purple in my Hemi.
I stay right on spec with my Jeep GC though, book calls for 10w30 and it gets 10w30 RP, so I'd get no bulk discount either way you look at it...