start using synthetics?

Any thoughts or experience of using Auto-RX?

I've got a 200,000 mile 90 XJ Ltd 4.0 Auto, and I put 10W30 synth in it a couple of thousand miles ago when I bought it. This seems to be cleaning the engine out very slowly, but I'm curious if the Auto-RX treatment would help. Compressions are a little low at 110 to 130, mileage is about 12mpg, oil pressure is low at 40 cold, 20 hot, and power is probably a little low - I'm thinking of going to 20W50 to see if it sorts out the oil pressure, although I may have to replace the main and bottom end bearings if that doesn't work.

The Auto-RX site has lots of very positive feedback that suggests it is the solution to everything except world peace and airplane seats, but then again I wouldn't expect them to highlight the shortcomings of the product...

So - thoughts, suggestions, whatever - bring it on! ;-)
 
If you are worried about the gunking up of old non-syn oil then do a motor flush. I prefer the gumout engine flush. never run engine flush with more than a qt under full, then engine flush itself i3 4qts. So with a 4.0, drain all but 1 or 2 qts of oold oil then add 4 qts of motorflush. Start and let engine run for 10 mins, or start and shut it off to check oil level and make sure this is/isnt enough oil to your staisfaction, then start it up again. Oh yeah leave you old oil filer on while its flushing. After 10 min, drain oil and change filter and put new filter on and add new syn oil. Thats all it takes. I ran pennzoil 1030 with a pz34 oil filter till 75k, then i used pennzoil high milegae right after for 1 oil change. after i used if it started to make the filter stud and rear main seal leak, which the jeep hasnt lost a drop of oil perviously. The next oil change i flushed the motor and started running mobil1 1030 with a wix filter. Runs better than it ever has, no longer ticks for about a min at start up when its cold and hasnt leaked a drop of oil and after 5k miles every oil change the oil still looks clean. Now i live in texas where the climate can be 104 in the summer and 10 in the winter and i havent noticed any differences in how it performs in either ne.
 
Should be no problem with doing the change over. Change the oil and filter, clean off the dipstick. As you run check the dipstick and look at the hash marks on the stick. When you can't see them anymore change the filter and add a quart, keep doing this till you reach the oil change interval you have decided on. The synthetic will clean the internals and the oil will get dirty fast, very fast so I'd look the dipstick over every time I got gas.
I run Mobil-1 in all 4 of our vehicles, 98XJ w/289,000mi, 2 97TJ's w/140,000 & 155,000mi. Wifes Oldsmobile w/40,000 on a jasper engine, old engine water pump failed around 155,000mi and the engine overheated, warping the heads, hence the rebuilt engine. We just picked up a 94YJ/5speed last nite and will be doing that one too.
The TJ's both had over 100,000 when we got them and they took the mobil 1 with no issues or leaks.
Filters I use are Mobil-1, K&N and Mopar. I tried a Purolator and was not happy on cold mornings when it took a full 30 seconds for the oil idiot light to go out, never had that problem with the others. Now that I have gauges in the XJ [replaced the cluster] I have almost instant oil pressure no matter the outside temps.
 
Okay so your saying you can run the Mobil1 from the start? I had my motor rebuilt and had planned on starting out with the Mobil1 but the mechanic told me to wait till I got I believe he said 5000 miles on it. I have only got about 1300 miles on it so I can run it now?
 
87jeepster said:
Okay so your saying you can run the Mobil1 from the start? I had my motor rebuilt and had planned on starting out with the Mobil1 but the mechanic told me to wait till I got I believe he said 5000 miles on it. I have only got about 1300 miles on it so I can run it now?
Click to expand...

It all has to do with tolerances, most mechanics and most shops don't rebuild a motor to the tolerances that the computer and robotic machines can. That 5,000mi interval is pretty much to allow the rings to seat in the bores. If they don't seat right you end up with lousy compression and oil leakage.
One HD/Indian mechanic/engine builder I knew would take a newly rebuilt vtwin, minus heads, and immerse it in a large tub, over the tops of the jugs, he'd then attach a chain to the crankshaft and attach that to an electric motor, the tub was full of very fine machine oil, think 3in1, turn the electric on and run the engine at varying low speeds over a few days. Was it a good way to do it, guess so, he had a very long waiting list and word was his engines were the one to have in your scoot.
 
87jeepster said:
Thats what he said, but I remeber paying extra money for them to run the motor for awhile to get it good and oiled.
Click to expand...

Normally when you rebuld a motor, new cam, lifters, etc it HAS to be run in according to the cam manufacturers profile. Some require like 20 min at 2500rpm and then down to 1500rpm for x minutes and then back up. Then each engine builder has their own 'mojo' they like to do that can range from sprinkling some holy water on the top of the air filter to running the snot out of it for a half hour or so. I would follow the builders/mechanics suggestions to the letter, that way if there is a problem it's not your problem :D it's his...
The one exception to this is, I'd change the oil filter a few times between that recommended 5000miles, I'd pop a new one on every 300 and add a quart of his recommended oil. The only thing dirtier than a rebuilt engine is a new one. I've seen and had brand new engines that still had black casting sand in the passages, my 76 dodge vans 440 intake manifold comes to mind which is why the thermally controlled choke would not work right, the cross over on the intake was packed solid with casting sand. I'm just glad it was a thermal passage.
If you ever buy a new car or truck cut open the first filter but do it while sitting down because it will shock the heck out of you...
 
Last edited:
Jazclrint,

Whose synthetics are you using in the tranny, diffs and xfer case???

I just picked up a 2000 XJ and will be changing over to Mobil1 in the engine. I'm a big proponent and use the stuff in all of my good equipment.

Thanks,
Jay in MA
2000 XJ

jazclrint said:
............. My whole Jeep is full synthetic now. Manual tranny, transfer case, differentials, and motor.
Click to expand...
 
Switched to Mobil 1 synthetic at 67K on my 99 (bought at 62K) and with in say 500 miles my oil pan gasket started leakin. But then it stopped. Then the rear main started leakin about 1500 miles after than (now at 2000 miles on the first run with synthetic). And now, I've got about 2500 on the first run, and they're both leaking! Nothin too drastic yet, but the oil pan is slowly getting worse. It was just leaking at the front of the engine, but now it's leaking all around the pan, down the oil filter, onto the starter (yeah, great place for oil huh?).

Call me crazy, but i'm gonna keep runnin Mobil 1 in it. I want to keep this thing a long time (gotta get me through the last year of H.S. and through 4+ years of college). The way I see it is, these seals were probably about ready to let go anyways, and I just sped up the process a tad. To my understanding, the rear main and oil pan seals are very prone to leaking after a while on the 4.0. Fortuneately (or unfortuneately) I have to replace one to replace the other, so I can knock them both out in one day.

I've already done the valve cover gasket, that started leakin with in 1000 miles of my purchasing it.

Upon switching I did notice the "cold knocking" the 4.0 is known for quieted down significantly compared to regular 10W30 oil, as well as the idle has smoothed out a bit, and it does seem like it ran alot better in the mid and upper range.
 
Been debating this myself and really totally unsure what to do at this point.

'90 Pioneer 4.0 Auto. 200,000+km Valve cover upgraded and rear main just replaced so I shouldn't have a problem with it leaking there. Oil Filter assembly o-rings I do need to do though. Have them, but just don't know how to put them in as of yet.
Anyways, right now I'm running 20w50 and was going to go to 10w40 for the winter [at the next oil change] but should I really go synthentic? I'm not sure if it's a good idea or not at this point with the mileage on the engine. Last oil change I started using GM's EOS with the oil, and they as well have something you put into the oil just before you do an oil change and run it which is supposed to help get a lot of the gunk out.
Just not sure which is the best choice.
 
sidriptide said:
i dont think so... but my personal experience with changing to synthetics on a well used engine have givven me mixed feelings on doing it again... i changed a ford 2.5L with over 100K on it over to mobil 1 and it ran AWESOME.. increase in mileage, ran smoother and quieter.. sounds like a commercial but it was that noticable.. but conversely i had a new 99 TJ with a 2.5L and at 7500 miles i went with Castrol synthetic and the rear main started pissing within only a few days. back to petroleum and it stopped.. went to Mobil1 and it started again...
i like synthetics and run them in everything but tranys and engines right now... my next new engine will be broken in with royal purple....
Click to expand...

I feel like I wrote the above quote. I love the synthetic stuff and have transfused many >100,000 mile vehicles with no leaks BUT.....

I just transfused the 2000 Xj that I recently bought. 116,000 miles and no leaks until I changed over to Mobil1 10-30. I bought it from the original owner and the engine has had regular 3K changes and is very clean inside. It is wizzing out of the rear main seal now. I'll run it for a bit and see if it stops. If not, I'll do the next oil change with 3 quarts of Mobil1 and 3 quarts of a dini oil and watch for leaks.

I was sceptical of the talk of oil leaks but it looks like there are vehicles that just don't like the stuff....damn.

Jay in MA
 
Jay
Mine did this as well. I switched over to synthetic at 106k i think. Jeep was good for a while, then started dripping very lightly. I switched to a blend, and its been drop free ever since. kinda bummed though, I would like to run full synthetic.
 
Just did my rear main actually as it finally went, and debating whether to stick with the dino that it's always had, or is it better to go to a blend? Just not sure if it's worth it or not.
 
Onthe subject, have a Q?
We got our first XJ on 10/91, an 86 wag. 2.8.V6, Still in the familiy. Like it so much brother got one, and then it came my time. I drive a '89 4.0 210K on the engine when bougt. no oil leaks of any kind, going on 3 years and 35k added, still no leaks. change the oil every 3000 miles on the dial. use castrol 20w50 drive hard. and fram extra tough filters. add about 1/2 quart to keep the level until' the next rutine oil change, oil comes out so, so. I think it can go another 500 miles, I travel about 300-350 miles a week, live in Ensenada Baja, Work in Tijuana Baja. about 90 minutes drive each way.(south of the border with San Diego CA)
I know I put to much info.
Q?
can some one give me their opinion on if it's worth the money and the risk to put synt. on this very high millage engine?
the avarege temp in so.ca. is like 70 F year round, so extreme temps are not an issue, nor the traficc jam, do a little off road, but nothing compare to what I' seen here, just take the family to the sand dunes and some time to the local mountains. nothing extremely O.R.
any and all coments are apreciated.
thank's
 
Much as I love the stuff I probably wouldn't use it in your vehicle.

I look at it like I look at vitamins....you feel like your doing something good for yourself but who really knows.

Until this past weekend I didn't think it would cause leaks....I wuz wrong.

I like not having to be under the cars every 4K miles but as a result I'm probably not checking other things as regularly as I should.

Jay in MA
 
Jay Welch said:
Much as I love the stuff I probably wouldn't use it in your vehicle.

I look at it like I look at vitamins....you feel like your doing something good for yourself but who really knows.

Until this past weekend I didn't think it would cause leaks....I wuz wrong.

I like not having to be under the cars every 4K miles but as a result I'm probably not checking other things as regularly as I should.

Jay in MA
Click to expand...

Good point!
 
XgeekstarX said:
i regret going to synthetics. my rear main is leaking like it's no tomorrow and it wasn't leaking before i changed over. i'm going back to regular castrol to see if it stops the leak.
Click to expand...

That may work, but honestly, you may be in for putting in a new rear main. From what I've been told, it cleans things out more than dino does, and that being said, if it has cleaned as such, then even going back to dino, may not have it sealed like it was before you switched.
That's the big problem/debate I see about going to synthentic from dino on higher mileage engines. The cleaning ability is good, but it can cause leaks to start you didn't have before.
 
cykaaro said:
That may work, but honestly, you may be in for putting in a new rear main. From what I've been told, it cleans things out more than dino does, and that being said, if it has cleaned as such, then even going back to dino, may not have it sealed like it was before you switched.
That's the big problem/debate I see about going to synthentic from dino on higher mileage engines. The cleaning ability is good, but it can cause leaks to start you didn't have before.
Click to expand...

it's worth a shot though. i'm thinking of getting the generic housebrand oil and a cheap filter just to see if the leak goes away. if not then i'm only out about 10 bucks.
 
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