what oil to use

Back ground. I have a 91 4.0 HO XJ. coming up on 189K on the clock.
I am considering switching to synthetic oil. Leaning towards royal purple because I work at a auto parts store and get a 25% discount.

Just wanted to know what everyone thought about switching to synthetic this late in the game. Or any advise you can give to get the most out of this motor. It runs great, just want to keep it that way.

homebrew said:

Just wanted to know what everyone thought about switching to synthetic this late in the game. Or any advise you can give to get the most out of this motor. It runs great, just want to keep it that way.

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If it ain't broke, don't fix it?

I've been pretty happy with Castrol GTX High Mileage formula for a few years now; does a great job of conditioning seals and doesn't cost much more than the regular stuff.

casm said:

If it ain't broke, don't fix it?

I've been pretty happy with Castrol GTX High Mileage formula for a few years now; does a great job of conditioning seals and doesn't cost much more than the regular stuff.

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I've been using valvoline maxlife with the same effects. My general plan is to run maxlife for a while, then try the switch to synth. It may be a stupid idea, but I'll try it.

i ran mobil1 in my 96 for about 30k after the 190k mark. i had a slight rear main leak before the switch and after a few thousand miles the leak dissapeared.(very strange when switching to synthetic). i threw a rod in the motor around 227k (nothing to do with the oil) and noticed that everything was very clean in the motor none of the usual sludge. maby the motor was just clean to start maby the mobil 1 had something to do with it.

I've run only one type of motor oil in any of my vehicles, Chevron Delo 400. Picked up the habit from my dad who ran it in his tractor-trailers. Great detergent oil. Change your oil regularly at 1500 miles and you'll never see sludge build up. I've torn down multiple engines that ran Delo and they looked emaculate inside.

homebrew said:

Back ground. I have a 91 4.0 HO XJ. coming up on 189K on the clock.
I am considering switching to synthetic oil. Leaning towards royal purple because I work at a auto parts store and get a 25% discount.

Just wanted to know what everyone thought about switching to synthetic this late in the game. Or any advise you can give to get the most out of this motor. It runs great, just want to keep it that way.

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Dont bother runing synthetic,Unless you have paycheck's burning a hole in your pocket.

My advice,run Mobil Drive Clean 5000 (depending on blow-by)10w40-summer,
5w30-winter $1.77-2.00qt at almost any wally-mart

Change every 2,500-3,000 depending on how it looks when coming out.

I don't know if I would switch at 189,000 miles, but I would switch at 100,000 and I did hehe. I run mobil 1 and even though it is expensive I feel better with it in there. Only reason I ever switched over was I saw a thread where a guy opened up a motor that had been put through its paces with mobil 1 synthetic and had a lot of miles but it looked brand new. No sludge whatsoever. You can open similar motors that use regular oil and they just aren't as clean compared to the mobil 1 engine I saw. I am a believer in mobil 1-----------Kyle

I use Mobil-1 10w30 in summer, 5w30 in winter with a Wix premium filter.

I'd say you can go wrong with Royal Purple, Redline, or Mobil-1. They are all top-grade synthetics, and if you get a discount at work, the RP might be your best choice.

switch to purple and stay with it. my overall engine temp cooled 3-4* and i get better cold crank starts and more power at the gas i think i can feel.

Never even heard of Royal Purple till about 3 or 4 years ago. I know they advertise on trucks and HP TV but are their products any good ? Is it actually their own stuff or repackaged syn from somebody else ? Couple of speed shops around here carry it but it's a bit pricey compared to Mobil-1, about $1-$2 a quart more...I usually snap up 6 of the 5 quart jugs at walmart when they put it on sale then get a six pack of Mobil-1 for the 6th quart...

I would recommend any of the "big 3" synthetics to anyone wanting to keep their engine healthy for a very long time. I work in an R&D lab with folks from all over the engine building, testing, racing, and design fields (ASC McLaren, Chapparal, John Deere, Cummins, Cat, Roush, etc.). It has been brought up several times and all agree that they have seen imperical data that shows the benefit of sythetics. Wear is reduced, power is improved, and you can go longer between oil changes with the synthetics if you keep your engine tuned up as needed.

I run Mobil 1 in everything I own or will ever own. Valvetrain noise on my SHO (120k) nearly disappeared when even ignoring the valve shim adjustments due every 60K (not me, the previous owner) and went from using a 1/2 quart every 3.5K in my F-150 (125K) to 1/4 every 7k with the synthetic. My XJ is the first vehicle (other than a couple of Gixxers) that I have ever owned with less than 60K on the odometer when I purchased it, so I looked for what ever would keep the junk I was rolling going the longest.

use synthetic! i am in the process of helping a friend of mine swap the engine in her landrover. its a rarely driven 95 with 80,000 miles on it. the bottom end lost the bearing caps because of hack job engine work, but when we pulled the valve covers we couldn't see any of the valve train because it was covered in a 1/4 inch of caked on black deposits from running cheap oil. Thats why i run synthetic, it might hurt a little every 3000 miles, but i won't have the big hurt of a shot engine down the road.

RichP said:

Never even heard of Royal Purple till about 3 or 4 years ago. I know they advertise on trucks and HP TV but are their products any good ? Is it actually their own stuff or repackaged syn from somebody else ? Couple of speed shops around here carry it but it's a bit pricey compared to Mobil-1, about $1-$2 a quart more...I usually snap up 6 of the 5 quart jugs at walmart when they put it on sale then get a six pack of Mobil-1 for the 6th quart...

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its their own stuff. its the color purple. couldnt be other oils repackaged. supposed to run 12,000mi.
http://royalpurple.com/techa/whyrpa.html
wheter these facts are true, i duno. either they have one nice oil or they are lieing. i have been very pleased since running it in my xj.

homebrew said:

Back ground. I have a 91 4.0 HO XJ. coming up on 189K on the clock.
I am considering switching to synthetic oil. Leaning towards royal purple because I work at a auto parts store and get a 25% discount.

Just wanted to know what everyone thought about switching to synthetic this late in the game.

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Not a good idea to switch to synth with such a high mileage. Synth will wash away deposits from old seals and gaskets, causing them to leak. The rear main seal is the biggest PITA to have leak on you. Another problem is that the synth will break down any sludge deposits you may have inside the engine, and these could get caught in the oil pump pick up screen. Result? A drop in oil pressure.
Just stick to a good quality, brand name dino oil. The manufacturers recommend 10W-30 Castrol GTX.

Synthetic Oil flows more readily than Conventional Oil, as well, the molecue is engineered to be polar, meaning it clings to metal and crawls along the surface, like capillary action.

Its because of that, that Synthetic has a tendency to leak a little more than Conventional Oil.

I've switched to Synthetic from Conventional Oil in hi-mileage engines before and never had a problem. It was always benificial, a little higher oil pressure, qiueted valvtrain noise and ran a little cooler and smoother. If the motor had leaks, the leaks tended to be just a tad worse, but not really bad, NO drips, the motor just tended to be a little wetter with oil in the leak areas than before.

I've never ran into problems with sludge flaking off and creating problems. Sludge is bad, you want to get rid of it. If the motor is sludged up so bad that Synthetic Oil is going to make it come off in chunks and mess up the motor, you motor was shot anyways. If you run into a drop in oil pressure, change the filter, its getting the dirt sludge out of the motor. I've never had it happen.

Synthetic is superior in everyway, it especially keeps the motor clean. The only thing to watch out for is the leaks. The leaks are overblown, I've never had a problem with leaks and most people don't, usually the worse you'll see is that the existing leak is just a little wetter with a little extra oil.

The Cost of Synthetic is a valid aurgument, it is often overkill for most motors, with cheaper conventional oil doing more than an outstanding job of protecting the motor, but you pay 2-3 times as much for the oil, for protection that you really don't need in most cases.

I'd give it try, if your so inclined, see what happens, it can't hurt, you can always switch back. Synthetic is 100% compatible with conventional motor oil, so there is nothing special about switching between each other or mixing them.

I will agree with many synthetics are great oil for an engine but you have to remember "when" is the important question. Switching to synthetics should be done early and usually between 70k-90k miles, if done after that you might end up hurting the engine by freeing to much crud thats actually holding it all together if you know what i mean. Another problem at such high mileage might be leaks, since synthetics have smaller molecules than regular oils, they tend to slip by areas that normally would be ok.

At 189k especially i would just stick with whatever you have been using, it seems to be doing the trick anyways . Remember be consistant and use good oil with a good filter and i think you should be ok.

pete

get on the web and go to "bobistheoilguy".. that forum was started by a bunch of petroleum engineers out in Texas, and they will tell you any and every thing you ever wanted to know about lube oil and filters.....yours is a common question on that forum.

Bought mine with 121,000 on the odometer. Unknown oil change or type history beforehand, but it had a slight main seal leak. Put Mobil 1 10W-30 in a few days after the purchase and (oddly or coincidently) the main seal leak stopped within 2,000 miles. Seems to have more power and run smoother now and hasn’t leaked since. I haven't experienced any problems with sludge, clogged filter, or anything else and I have no plans on changing the oil more frequently than 6,000 mile intervals.

The previous owner of my XJ used Mobil 1, so I'm doing the same. Yeah, the cost sucks. The best prices I've seen are at Walmart. You get the 5 qt jug and a 1qt bottle for something like $26. Not too bad.

I've switched to Synthetic in motors with more than 175k Miles and never had a problem. In fact, the motor ran smoother with less noise, like lifter tick.

Synthetic oil properties, like polar molecues, etc, does tend to flow more oil thru a leak. So, if the motor has lots of leaks, synthetic may make it worse. Give it a try, if it leaks to bad, then switch back to conventional oil, if your not willing to fix the leaks.

I'm not much for these schools of thought about crud holding an engine together. Think about what this is saying. The motor is being held together by dirt and garbage, touch it the wrong way and it will all fall apart. Oookaay, but you drive all over the place with the same motor?

This is like the school of thought about transmission problems, where you get someone that warns you not to change the fluid and filter in a tranny thats not working right, because it might do something to the shifting that will only make it worse.

OK, sure its possible that changing fluid or switching to a different type of fluid could cause dirt to break free or changes that pushes your motor/trans over the edge and it fails or malfunctions. BUT, the fluid is not the cause, its the motor/trans being in such bad shape its was on its last legs and was going to fail any minute is the true cause of such a thing. Its extremely rare, but if its happens, it was only brought on a few miles earlier than it would have happened if you done nothing at all.

So guys, if you think dirt might become unlodged and destroy your motor from switching oil types, then rebuild your motor because it needs it. If switching to synthetic is going dislodge enough crud to damage the motor, than there must be enough in the motor already that it could break free on its own at anytime and do the same damage. Fresh oil will clean better than old oil, so by this logic, if I have a dirty motor, NEVER CHANGE THE OIL AND IT WILL LAST LONGER because you never want to take a risk of breaking some of that dirt free and having it float around the motor.

All oils have cleaning properties and they also have the potential to create sludge and crud as a byproduct of their use. Using the proper oil and appropraite quality in the right conditions with a correctly working motor, the cleaning properties of the oil should outpace the byproduct production of sludge and crud.

If sludge and crud is building up in the motor, its because the byproduct production is outpacing the cleaning properties of the oil. It could be because of the poor quality of the oil, something is wrong with the motor (malfuntioning CCV system) or the conditions you use the motor in, or how often you change the oil.

Synthetic oil does NOT have some miraculous cleaning property or high detergeant additive package to clean up motors. Synthetic oil, since it so well engineered to do its job, contains very little of the byproducts that make sludge and crud, it resists breakdown much better to help fight it turning into sludge and crud, as well. This why motors running synthetic for a long time are so clean, they don't leave behind any deposits/sludge/crud like other oils. They may clean as well or a little better, but they aren't some sort of SUPER CLEANER, they just don't leave behind deposits like regular oil does.

If your motor is extremely dirty, switching to synthetic should clean it up, over time. If your motor is so dirty that switching to synthetic breaks free chunks of dirt that damages the motor or lets seals leak, then you motor was toast to begin with, the new oil only brought on the failure a few miles earlier than it would have happened on its own. Like I said before, fresh regular oil will clean better than old, as well, so wouldn't fresh oil have the potential to break off dirt chunks as well?

I've seen lots of speculation about what can go wrong when switching to synthetic oil in high mileage motors, but I see very little actual cases of people complaining of actually suffering any of that speculation. Instead you see a lot of endorsements with people saying that switching to synthetic was an improvement.

Weigh the pros and cons and decide on that, I just don't believe you should believe you should make decisions living in fear that your motor is being held together by dirt/sludge/crud and anything you do to improve it may make it fall apart. Its not going to happen, if it does (your that 1 in a million) then it was going to happen anyway, because the motor was ruined to begin with, you just didn't know it yet.