I was just looking at the lube specs in my owners manual, and there's a note that says 4.0's use 10w30 motor oil ONLY... Is that true? I've always put 5w30 for the winter

 

i think that 5w is better for cold weather and 10w is better for summer, but mine is 5w mainly......oh ya mine is a 3.0..

look in the ownerz manual for that

 

i use 5w30 all year long... thats the only type listed in my manual so its what i use, i dont swtich to a thicker oil in the summer....

 

It will not hurt a thing to run 5w30 all year, these engines have pretty close tolerances so you really dont need a thicker oil, as for most newer fords. All of the newer V8s and it seems every other ford engine(new) is using the 5w20. That stuff comes out like water!!!

 

10w30 and 5w30 are the same thickness oil at operating temperature

they just have different winter pump ratings

 

so it won't hurt anything to run 10w30 in the winter as well then?

 

10w is thicker than 5w when its cold. I run mobil 1 5w30 all the time in my truck. Its a 2000 4.0L 4X4 auto

 

Just use 5w30 fully synthetic and call it a day.

 

I use Mobil 1 5w-30 all year

 

I'm scared to switch to synthetic cause I don't want to have to be ripping apart the oil pan to put a new gasket and whatever in when it leaks

 

Theres nothing wrong with running one type of oil all year round. If you think about it its most likley the best way to go. I use 5w-30 all year round.

 

Well reguardless of what kind of oil you have in, if it leaks you're gonna have to replace the gasket. BTW it's not hard at all to replace but synthetic is no more likely to cause a leak than normal oil. Wean it on a synthetic blend for one or two oil changes then switch to fully synthetic.

Synthetic keeps it's viscosity no matter what the operating temperature(I think).

Maybe it's all in my head but my 4.0 seems to run a lil smoother w/synthetic.