Oil for 4.0L OHV

[sgm42c]

My question is this: What oil (weight, type, brand, etc) do you use or recommend using in a 4.0L OHV engine with just over 157k miles on it. I've read (not on this forum) that dropping down in weight may increase fuel economy with almost no negative effects to the engine, but, I'm not sure I believe this. What has been run in it up to this point is a fully-synthetic 10W-30 (Mobil 1, I think. The truck was my cousin's). Should I just stay safe and run the same oil or is there any benefit/harm to changing to say a fully-synthetic 5W-30 or 0W-30?

Any information would be greatly appreciated. Thank you!

 

[Jon94]

5w-30 and 0w-30 are the SAME thickness as 10w-30 when the engine is at operating temps (they're all 30 weight oils). The only difference is the first number- 0, 5, 10. This refers to how much an oil thickens up in freezing temperatures. A 10w-30 will thicken up more than a 5w-30 or 0w-30 (which is not good). Using a 5w-30 or 0w-30 will not harm anything, but you will NOT gain any gas mileage.

 

[herebyproxy]

Any oil

You can't go wrong with any 5-30 full synthetic.......

 

[unclemeat]

You can't go wrong with any 5-30 full synthetic.......

That is what I run.