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Oil additives for high mileage xj

8

805cherokee

NAXJA Forum User
Location
California
Hey guys I am new on here and I just changed the oil and oil pan gasket. I want to know if anyone has or suggests adding bestline oil additive to an xj with 205054 miles?
 
Stay away from Lucas. It is just an oil thickener, there are multiple analysis that have been done on it. The last thing you want is something thickening your oil and making it take longer to get to the bearings on a chilly morning.

Use a good high mileage oil like Valvoline MaxLife 10w30 or Pennzoil High Mileage 10w30. If you'd like a heavier duty oil, go for Rotella T 10w30. All will work well. If your oil pressure is on the lower side, use a 10w40 or Rotella 15w40.
 
Lucas is just a super thick, detergentless oil. So in addition to make it flow less on a cold start, it dilutes the additives in the oil.

I have used Pennzoil High mileage in the past and will be doing the Valvoline MaxLife this time around. I'm too lazy to change a few leaking gaskets and it seems to help!
 
The Jeep 4.0 L is 1970's technology, there is no need for any special oil additives. Some people do use diesel engine oil for the extra ZDDP that is in the diesel oil. If the ZDDP is necessary for the Jeep 4.0L has not been proven.
 
The only time ZDDP may have been needed in an XJ was 14+ years ago when the camshaft was new. Now that the camlobes have been work hardened, there's no need.
 
Only thing I've ever really used was Lucas.... Yes it is a thickener/thicker oil.... But it also sticks to the moving parts much better so there's less friction on cold start ups.
Some of these other oil additives I've tried (to stop that pesky 4.0 mystery leak) don't work. Last one I tried was blue devil and it poured in like water. And it didn't do anything new as far as I can tell.
 
I always run 1-quart of MMO, in place of a quart of oil, when I do my oil changes.
 
Agreed. (Good) modern engine oils have a lot of chemical engineering know-how put into them and shouldn't require the use of any special additives. In fact, adding additives to them can actually mess up the formulation of the oil, rather than help it. That being said, changing a high-mileage 4.0 that has seen nothing but cheap conventional it's whole life to a synthetic oil can cause oil leaks since the additional detergents in the synthetic oil can knock loose crud around the seals that was keeping them from leaking in the first place. For what it's worth, I run Mobil 1 High Mileage 10W-30 synthetic in mine with a K&N oil filter. I will also say that I don't buy into the 7,500 mile "normal use" oil change interval in the owner's manual. Thus, I usually split the difference between that and the 3,000 mile "severe use" interval and change my oil every 5,000 to 5,500 miles.
 
JeepNoob said:
Agreed. (Good) modern engine oils have a lot of chemical engineering know-how put into them and shouldn't require the use of any special additives. In fact, adding additives to them can actually mess up the formulation of the oil, rather than help it. That being said, changing a high-mileage 4.0 that has seen nothing but cheap conventional it's whole life to a synthetic oil can cause oil leaks since the additional detergents in the synthetic oil can knock loose crud around the seals that was keeping them from leaking in the first place. For what it's worth, I run Mobil 1 High Mileage 10W-30 synthetic in mine with a K&N oil filter. I will also say that I don't buy into the 7,500 mile "normal use" oil change interval in the owner's manual. Thus, I usually split the difference between that and the 3,000 mile "severe use" interval and change my oil every 5,000 to 5,500 miles.
Click to expand...

Don't run K&N - avoid them like the plague. They let too much fine dirt get through. The DSPO ran a K&N and my first oil analysis was scary with the level of silica. I switched to an AEM Dry Flow (same as we run on the desert racer) and haven't had a bad analysis since. I run Mobil 1 High Mileage 10-40 with a Motorcraft FL-1A filter. Also with the analysis, I have found that 7500 miles is just fine, and the lab is saying that I could probably extend to 10K miles based on the test results. I also don't buy into the "if you switch to synthetic it will leak" hype. It had 180K miles when I bought it, and now has 216K and I had nothing start leaking when I switched to synthetic.
 
K&N oil filter. They have a 1" nut on the end of the filter which makes putting it on and taking it off a bit easier and IIRC, they're supposed to filter down to 10 microns. (15 seems to be the standard for most oil filters) but filtration ratings on oil filters is a whole 'nother can of worms...
 
I ran a K&N oil filter once. That was all it took. I had metal shavings show up on my dip stick. I don't know if I just got one bad one or what, but never again. For the price, the Ford is hard to beat. It has all the good stuff inside, plus it is bigger than the stock filter.
 
First thing is open the oil cap and look around the valve train with a flashlight. What does it look like? If its lot of black sludge you probably need to clean that out with a quart of MMO in frequent oil changes until it washes out.

If the valves look okay (brown is okay) then get a couple of compression checks, maybe a leakdown check, if you have decent compression leave it alone. If you have bad numbers you may want to use a thickener, but start with something like 20w50 before going all the way up to Lucas

Wix or NAPA Gold filters are the best, will take the crap out of the engine the best
 
I've used a K&N once or twice and never had any problems. I used the Ford FL1a for years but as the cost has risen closer to he Wix/NAPA Gold filters I have switched to them for the equivalent size.
 
DieselSJ said:
Don't run K&N - avoid them like the plague. They let too much fine dirt get through. The DSPO ran a K&N and my first oil analysis was scary with the level of silica. I switched to an AEM Dry Flow (same as we run on the desert racer) and haven't had a bad analysis since. I run Mobil 1 High Mileage 10-40 with a Motorcraft FL-1A filter. Also with the analysis, I have found that 7500 miles is just fine, and the lab is saying that I could probably extend to 10K miles based on the test results. I also don't buy into the "if you switch to synthetic it will leak" hype. It had 180K miles when I bought it, and now has 216K and I had nothing start leaking when I switched to synthetic.
Click to expand...

Everything you said is true in my case and especially on the 7,500 miles oil change. As a matter of fact with a good synthetic and 80% highway miles I do oil changes at 10,000 miles. My 280,000+ miles XJ which I bought at 125,000 miles maintains 35 psi oil pressure and 60 psi hot. No, synthetic oils do not cause oil leak.
 
Synthetics can cause leaks. When I bought my 93 W250 I switched it to synthetic. It had been leak free and then the rear main opened up within a few days.... You can argue that the seal was holding because of build up from running conventional which is fine with me. I use synthetics in my vehicles ever since one of my VW diesels required it about 15 years ago. In later vehicles we found that synthetics virtually eliminated timing chain wear. The timing chains would "stretch" to their wear limit within about 150,000 miles with conventional...
 
I've been very happy with synthetic blend 5w30. I may try full synthetic on my next oil change. My xj has 217k on its odometer.
 
I use Brad Penn 10w30. It is a semi synthetic, has the proper ZDDP that our engines were designed around and can be bought on Amazon Prime ;)
 
I got my 1999 2.5L with 130K on it. When I crossed over the 225K mark I started using 20W-50 non-synthetic. Now has 310K and still has 50psi oil pressure. Have never used any additives.

At around 260K I had the timing chain tensoner come apart and a piece of it got under #1 piston braking the skirt off it. When I replaced that piston I was shocked at how little lip was in the piston cylinder and how good of shape the rod bearings were in after 250K.
 
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