MC 5W-20 in Jeep 4.0

[HawkeyeScott]

I’ve been watching BITOG from the weeds for a few weeks now, studying and soaking up as much as possible. What a great resource. I appreciate the opportunity to join in.

I’ll post the question that brought me to the website in the first place:

Is MC’s 5W-20 in my wife’s Jeep Cherokee (97K miles) HURTING the engine? I’ve had the Ford dealership (where a friend works) do the last few oil changes, and naturally, they used 5W-20. It honestly took a few months for this to dawn on me, and a few days more to really start questioning it. I would have drained the oil immediately, but realizing it was a syn-blend, I kept it in there. Since then, I made them go back to the recommended 10w30.

We live in NC Piedmont, where the summers are actually pretty mild. She may have driven in 98 or 99 degree temperatures 4 or 5 times this past summer when the 5W-20 was still in there. Nothing hotter though.

I get the idea this wasn’t the best protection for this motor, but was it necessarily harmful?

Also, on a side note, the engine is still really strong, but is nearing 98K. It seems clean after 3500 mile OCIs and there is no oil consumption. Why, at all, should I think about using Auto RX?

I should mention that we bought this car for this engine, for the sole purpose of driving it until my feet hang through the floorboard.

Thanks guys.

 

[Zaedock]

Run a search on Gary Allen and his experiment running 5W20 in his XJ.

...and also

 

[Zaedock]

Quote:

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Run a search on Gary Allen and his experiment running 5W20 in his XJ.

...and also

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Argh, can't edit my last post. FWIW, in winter I run Castrol GTX 5W30 in my severly beaten 2.5L '92 Wrangler trail rig and Supertech 5W30 in my '89 XJ 4.0L. I'm sure they get sheared down into the 20wt range. I wouldn't be overly concerned.

 

[sw99]

MC 5w20 is a great oil and I have considered running it in my Jeep also.

I run strictly 5w30 although the manual states that 10w30 is preferred. 5w makes my 4.0L run quiter and I have zero lifter tapping that seems to be so common in these Jeep engines. Since the 30 weight is identical, I figure the 5w at start up is the best choice. Since most of the wear happens at startup, why not run the 5w?

Who knows, maybe i'll eventually try the 5w20. For some reason the 20 weight makes me nervous in these rugged I6's.

 

[sw99]

http://63.240.161.99/motoroil/

Here is some awesome info. This helped with my decision to run the 5w vs. 10w. The 101,102 & 103 ones are more aplicable to this particular question. Good luck!

 

[KW]

The 5W20 won't hurt it as long as it has good hot idle oil pressure. I prefer 10W40 in my 4.0.

 

[Greaser]

Then again I use the 0W oils

 

[HawkeyeScott]

Thanks guys, for the info. so far.

I was obviously most concerned about the 'thinness' of the oil protecting during the summer months. I breathed a bit easier when I read on here than MC's 5W-20 is around 60% synthetic.

From here on out, as long as the car is in service in NC, it won't likely see anything but 5w30 or 10w30. Perhaps something heavier later in life...

 

[427Z06]

I'd look for a 5w30 that meets Ford's WSS-M2C929-A spec. That's something you won't find in a dino/syn blend GF-4 10w30.

 

[Gary Allan]

Assuming you have decent oil pressure, I think your main problem will be timing chain wear ..which some speculate that is the source of Fe in used oil analysis. Viscosity alone doesn't prevent this high Fe. I used Rotella T Synthetic 5w40 (Rotella T synthetic) and still had butt loads of Fe.

So, do a used oil analysis and see what's up with your engine.

I'm sending in my 5w-20 used oil analysis in next week regardless of mileage. It's over 4k ..which I think will be close enough to 5k to make a determination of suitability. I won't change the oil until the used oil analysis is returned,if then. I think I'll use Terry on this one. I've hand no consumption to date.

 

[Ramblin Fever]

If it were mine, I'd run Rotella synthetic 5w-40 in a heartbeat, and I'd run it year round without question. This is a very robust oil with good detergents, and can easily go for 5-7k miles.

This oil does not shear as fast as a 5w30 oil, gives you the cold weather starting factor with the 5w and the thickness of the 40 when the engine is at temperature.

In my opinion, you couldn't go wrong in any season or any driving condition.