2005 4.0L Oil

[JeepSD]

I just purchased a 2005 Wrangler X and it has 68K miles and has been running on 10W 30 non synthetic. If I want to switch it over to Mobil 1 synthetic oil will that effect the engine?

 

[frhrwa]

I'd dump the synthetic and go with a good oil like Rotella.. 5W30 or 5W40.. depending on how cold it is where you are.. the 5 is nice in colder weather, and the money you spend on that synthetic is just wasted to say the least..

 

[JohnnyO]

I tried Rotella T-5 10w-30 Syn Blend in the Jeep and got a used oil analysis that was very good. Of course I only ran it 3000 miles so ANY oil would look good but for whatever reason consumption was up with that oil and I added another 4 quarts over 3000 miles (another reason why the UOA looked good). Using 10w-30 Max Life I add 1 quart and 2 at most over 3000 miles.

Oil companies have been forced by the govt to use less zinc in motor oil because it will foul catalytic converters in cars that burn oil. It's no problem for newer engines that have roller lifters but in older engines with flat tappet lifters (like Jeeps) you need the extra zinc. High mileage oils have a little more zinc in them and diesel-spec oils like Rotella have a fair bit more because they don't have cats. In older I-4 and I-6 Jeeps I would use a high mileage oil even if it doesn't have high mileage. There is a high mileage version of Mobil 1.

 

[JPNinPA]

If you stay with dyno be sure it has or you add ZDDP. It will make a big difference in engine lifetime.

 

[JohnnyO]

If you stay with dyno be sure it has or you add ZDDP. It will make a big difference in engine lifetime.

Really either dino oil or synthetic. All SM and SN rated oils have less ZDDP (zinc). High mileage oils have more ZDDP. One tip is to look at the SAE rating circle on the back of the bottle and if the words "Energy Conserving" are NOT at the bottom of the circle then the oil probably has a higher amount of ZDDP. Or use a diesel-rated oil like Rotella 10w-30 or 5w-40.