mrfajita

Rotella T 10-30 and a WIX filter.

djb383

If most engine wear occurs at cold start up (any temp below operating temp), due to the oil being thick and flow is reduced, why would u want an even thicker oil at cold start? The lower the 1st number, the better the flow at less than operating temp. 0W40, 5W40, 10W40, 15W40 and straight 40 are ALL THE SAME VIS (40) at operating temp.

1991Jeep_Man

With you mentioning this, I was curious about something. When warmer weather does start around here (like spring/summer), I thought about going back to 10w40 instead of my current 5w40. My reasoning behind the switch is because I think where my 4.0 is older with higher miles, the 5w (being thinner) sneaks past the cold valve stem seals and what not since they aren't up to OT and filling in those looser clearances. However, since it's obviously colder in winter, I figured the cold oil wouldn't sneak past as much. Since warmer weather is upon us, I figured the 10w40 would assist in keeping oil from going past those seals. What do you think? Is this plausible, or I am totally wrong?

Btw OP, sorry about the little thread hijack here. But I would never be able to forgive myself for starting ANOTHER oil thread lol.

Passt

She starts every morning. I live in MD, and we did have a fairly mild winter, but even on the few freezing days we did have, I didn't have any issues.

413maxwedge

Because they think they know better than the one's that test these and other engine's for proper lube , and wear characteristics

fister1989

im running castrol 5w 30 synblend with a performance filter from advance in it seems to be really good

Luigivalenti

I have a 2001 cherokee sport with 147,577 miles, I was using valvoline high mileage 10w-30 and switched back to regular 10w-30. I would like to know with which one I should stay as well what oil filter I should use.

1991Jeep_Man

Go to engine oil aisle, close eyes, point, open eyes, buy oil youre pointing at (as long as it is something between 5w-15w and 30-40. Go to oil filters. Anything over $4 and fits, get it (except Fram). Have beer. Repeat in 5k miles depending on oil and driving habits.

Btw, nice necropost!

djb383

The valves are not part of the pressurized lubrication system....they r lubed/cooled by oil splash/throw. 0WXX oil is way to thick to make it's way past valve stem seals unless the seals r shot.......and a little oil by the stems at start-up is a great momentary upper cylinder lube. Switching to a heavier 1st number oil improves nothing.