'89 Jeep Wranger 6 cyl

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BigJohn

BigJohn

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I have a could of questions....

Recently, I purchased a Jeep Wrangler for my son. The engine had a bit of a knock, so we are changing the oil pump this weekend. When we dropped the pan, boy was it disappointing....sludge and gummy oil all over the pan....especially collected at the bottom. Anyway, I am sure the clean up and the new oil pump will help things out....but I have an oil question.

We have now reached the time of the year, where it is not uncommon for him to head out at about 6:30am in zero to 10 degree temps in the morning. We do not have a vehicle manual so I have no idea what Jeep recommended for that engine when new......but that is probably inconsequential. The engine has 160k miles on it. During the summer the engine seemed to like a mix of 10w40 and 20w50. It ran really smoothly and the knock just about went away. So I need a new soup to pour in her so that my boy can start up the rig on the cold mornings.

Is it out of the question to run a 5w30? I am sure the engine will consume some of this thin stuff, but if it runs good and starts easily in the mornings....then I don't mind topping off once a month.

Thoughts and ideas??????
 
I would use a Synthetic 5w30.

Mobil 1, Pennzoil Platnium, ect. with a short 3000-4000 miles OCI untill you clear some of that gunk out.


you may want to check out Auto-rx.
 
In 89 Jeep recommended for the 4.2L six either 10W-30 or 10W-40.

If you had that much in the pan, I'm sure some is in the top end as well. Some of that noise you heard might have been sticky valve lifters. I would run a mild short term flush in there like what Amsoil sells, only for about 15-30 minutes. Then change the oil out with your favorite dino 10W-30 and change it at least every 3K for two or three oil changes. Those are tough old engines and once half way clean should give you good service.
 
For winter months you should use dino 5W30 with 3-4k miles OCI, don't forget to check oil level every month or so, then 10W30 in summer with the same OCI of 3-4k miles. After 2-3 oil changes with dino 5-10W30 you can use synthetic 5W40 all year with OCI extended to 7-8k miles. Mobil 1 Turbo Diesel Truck 5W40 is a good choice for this engine all year in Colorado.
 
Why the instance of a 10w30 instead of a 5w30? I thought the first number simply meant the oil's starting weight.

Also, I really like the idea of a flush, so to speak. Will a flush or simply a short run (1,000 miles) of a light weight oil clear out the supposed gunk in the top?
 
Originally Posted By: Johnny
In 89 Jeep recommended for the 4.2L six either 10W-30 or 10W-40.

If you had that much in the pan, I'm sure some is in the top end as well. Some of that noise you heard might have been sticky valve lifters. I would run a mild short term flush in there like what Amsoil sells, only for about 15-30 minutes. Then change the oil out with your favorite dino 10W-30 and change it at least every 3K for two or three oil changes. Those are tough old engines and once half way clean should give you good service.


+1

Just flush it, then put in 10W-30...
 
Originally Posted By: BigJohn
Why the instance of a 10w30 instead of a 5w30? I thought the first number simply meant the oil's starting weight.

Also, I really like the idea of a flush, so to speak. Will a flush or simply a short run (1,000 miles) of a light weight oil clear out the supposed gunk in the top?



I would use nothing but a 5w weight oil. It allows for the best start up flow (short of 0w weights, but thats another topic).

A "flush" would clear some stuff out. It is said that some can dislodge a big piece of sludge and that in turn could clog something and break the engine.
Would a flush do that to your car???? 99% absolutly no.

However, I would not flush. I would just use Synthetic oil like pennzoil platnium. It is a synthetic with a lot of additives like Calcium to fight sludge. A few short runs of that stuff, then a basic 5000-6000 mile OCI with the Pennzoil would work out best in my opinion.
 
Well, fortunate for me that Pep Boys is selling PP (5 quarts) with a premium filter for $27. Guess I better jump on that while the price is right. So for a short run to get the [censored] out, should I go with a 5w20 or a 5w30 of PP?????
 
I have many Jeeps, ranging from stock to a 2000 TJ buggy. In winter, I run dino 5W30 in all of them. It will crank/start much easier. Also, many 5W30's are slightly thicker than 10W30's at 100*C.

If it were my Jeep, I would run 5W30 GTX, QS, or YB with a bottle of AutoRx and a Motorcraft FL300 or FL1A filter and call it good. If you reach 3000 miles by next spring, step up to a dino 10W40 or Delo SAE30 for the warmer months. That's all this engine will ever need.

Regarding the knock, run a tank of 93 and see how it sounds. A buddy of mine stored his '87 at my place for a year and a half and it developed a lower end knock one day. He was bummed. After trying to diagnose, we needed to put some gas in it. All I had was a can of 93 I use in my quads. After putting it in, the knock went away.
 
id go with the 5w20 for a short run. Thin oil will help clean some.

Then use the 5w30. PP.

Wranglers are A LOT of FUN!!!
I miss mine. Theres nothing like crusing around with no roof or doors!!!
 
For the winter months, a 5w30 oil would be fine. If you still want the "thick" but want the cold start properties, run a 5w40. I ran 5w40 Shell Rotella T syn in my '88 Cherokee with the related (but not the same) inline six cylinder.

My '88 Cherokee was originally a Colorado Jeep and ran on a 5w30 winter month / 10w30 summer month oil change routine. Since figuring out the engine ran just fine on any dino 10w30 or 5w30, thats all I run (but the Jeep is in Minnesota now..)
 
Originally Posted By: rg200amp
id go with the 5w20 for a short run. Thin oil will help clean some.



5W20 is not going to clean any better than XW30. If anything, it may add deposits due to burn off.
 
Originally Posted By: Zaedock
If it were my Jeep, I would run 5W30 GTX, QS, or YB with a bottle of AutoRx ......




Where can I purchase Auto-RX? Can I purchase locally in the Colorado Springs area? Will be finishing the oil pump job tomorrow and can't wait for a web order.
 
Last edited:
If you've already cleaned out the pan ..then under the valve cover, if carefully done, should do most of the job. The timing cover would be the biggest cached area of formations left untouched. With that much mass, I'd have a hard time with a solvent flush. While the odds are low in any unfavorable outcome, the dwell time is totally insufficient to do more than to reduce it a little. It might free up a few stuck lifters. That's why I would use Auto-Rx. Even that might take a couple of tries to get stuff removed.

The engine itself could care less what oil is used in it ..at least on the heavier end. For all apparent measures ..on the lighter end too. Most of the problems with 4.0/4.2 are typically valve noise ..and maybe a timing chain wearing out. I don't think I've seen more than a handful that have had bearing issues. Even those pushing big tires under extreme conditions (keep in mind that BIG and EXTREME are relative terms).
 
Originally Posted By: Zaedock
Originally Posted By: rg200amp
id go with the 5w20 for a short run. Thin oil will help clean some.



5W20 is not going to clean any better than XW30. If anything, it may add deposits due to burn off.


No oil is going to "clean the motor"

Thin oils are going to provide a but more "cleaning abiltity". it will help clear some sludge out.


It has been talked about before how the thinner the oil the better it would help clear some build up out.
 
Originally Posted By: Gary Allan
....Most of the problems with 4.0/4.2 are typically valve noise ..



Need some more advice on this noise..... The engine sounds like a diesel engine when the RPM's are at idle to about 2500, and then it disappears as the engine is reved. Also, the oil pressure gauge reads a high level until the engine heats up and then the oil pressure dips.

A local Jeep mechanic told my son that the first fix would be a new oil pump....hence our 'shade treeing' this weekend.

What do you think?
 
Last edited:
Originally Posted By: BigJohn
Originally Posted By: Gary Allan
....Most of the problems with 4.0/4.2 are typically valve noise ..



Need some more advice on this noise..... The engine sounds like a diesel engine when the RPM's are at idle to about 2500, and then it disappears. Also, the oil pressure gauge reads a high level until the engine heats up and then the oil pressure dips.

What do you think?


Perhaps its a exhaust leak? I had a crack in my manifold on my truck, it did the same thing your saying about the sound.

About the oil pressure-
As long as your oil pressure is normal at operating temp, I would not worry to much.
 
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