Manufacterer recommended oil weight

[SMD747]

I have a 1999 Ford e-150 van with the 4.6l v-8. Ford only recommends 5w-30 oil. I see on this site 10w-30 is more widely recommeded. Should I use 10w-30 in the warm months and 5w-30 in the winter? Does it really matter if I use 10w-30 all year long? Or should I stick with what Ford says?
What is the benifit of 5w-30 over 10w-30.

 

[GROUCHO MARX]

In the non-winter weather, I would use the 10w-30. If you're using a synthetic such as M1, I would use the 10w-30 all year.
JMO

 

[G-MAN]

Well, Ford actually recommends 5w20 for your engine now--they have retroactively recommended this grade for all 4.6 V8s all the way back to 1992.

If you don't want to switch to 5w20, I think 5w30 year-round should be fine, and I'd certainly use 5w30 in the winter months.

 

[dustyjoe1]

The 5w30 year round should work fine. You might want to give the Motorcraft 5w20 oil a shot though. In my opinion you are getting a better oil (synthetic blend) for pennies more.

 

[JohnBrowning]

You can use 5W30 if synthetic like M1 year round. I prefer M1 10W30 and you probably will too.

 

[jorton]

I think there is a conventional 10w30 you can use year round in your climate. It can be changed every 4000 - 5000 miles.

If you use 5w30 year round it should be changed every 3000 - 3500 miles.

I noticed Phillips 66 TropArctic 10w30 is really thin so I would use that year round.

Joe

 

[Ray H]

Ford's viscosity recommnedations (like Honda's, and recently, DaimlerChrysler's) are driven by the need to deliver the lowest possible CAFE fuel consumption averages to keep the Feds at bay. The 5W-20 oils, regardless of brand, have ALL shown remarkable performance in the UOA section, notably with less shear-back than conventional 5W-30s (mostly Group II, while most if not all 10W-30s are thought to be blends of Group I & Group IIs). That Motorcraft 5W-20, a synthetic blend (Groups II & III), is around $1.80/qt at discount is additional frosting on the cake. There continues to be a reluctance on the part of some to give these 5W-20s their due, but the UOA results just don't support the hearsay negativity.