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oil question

XJsport23

NAXJA Forum User
Location
georgia
My 98 just hit 150,000 miles, and I'm thinking about changing over to using a high-mileage synthetic instead of the standard oil I've been using. I dont think it's necessary because I know how tough these engines are, but considering the fact that I do need a couple more years out of it and that I've been adding more performance parts to the engine (intake, exaust, new injectors, ect...) it seems like a good idea. However, I've been told the XJ isn't going to like it if I switch over to a synthetic, doesn't make sense to me but I wanted to be sure. So if any of you have switched to high-mileage synthetics or know anything about this I would appreciate your help.
 
I use valvoline high mileage (or whatever its called) in the red bottle - its a synthetic blend. I swear by it.

EDIT: I've tried every high-mileage (not full syn) there is, and this stuff is the best IMHO. I just rolled 150k
 
Changing to synthertic in a high mileage engine sometimes leads to leaks because the synthetic is typically thinner and more slippery. You may want to replace some gaskets at the same time.
 
Yea I've heard about the leaking, but some quality synthetics are supposed to prevent leaking so there's no problem. I just want to make sure this will be an improvement on the amount of miles I can get out of the xj.
 
I use Amsoil oil, buy it from there website. I Changed my oil Nov. of 06, Joined the army in January of 07, it sat for six months never ran. I came home and fired it right up and the oil was still clean, I then proceeded to put 2800 Miles on it within 10 day's 2000 of those within three day's while driving from Maine to Louisiana. Just changed the oil last week, Engine run's great, barks second with BFG All Terrains. You want the best, go Amsoil.
 
the po of my '96 had been using pennzoil(ugh...), i found a bunch of oil change receipts in the glovebox for some quICKI-lube place. i changed over to royal purple @ 169k and the only issue afterward was the oil filter adapter leaking. i fixed that and it's been happy for the last several thousand miles. if something starts leaking after the switch, it was probably marginal to begin with....so if it leaks, just fix it.
 
Switching to synthetic is a great diagnostic tool. Wherever it leaks, is a potential problem spot.

But I can't forsee any problems by switching to an oil made for high mileage engines. But seriously, you may find some leaks. That's a good thing. It gives you a chance to fix it before you have a problem, like letting water in or something.
 
jesterbomb said:
Switching to synthetic is a great diagnostic tool. Wherever it leaks, is a potential problem spot.

But I can't forsee any problems by switching to an oil made for high mileage engines. But seriously, you may find some leaks. That's a good thing. It gives you a chance to fix it before you have a problem, like letting water in or something.

I could be wrong, im no mechanic by any means, but i definetly "anal" about fixing problems, and i love to DIY. I agree completly with jesterbomb. When i got my Jeep from a buddy i did what i always do and changed all fluids \ all maintenance parts etc.. I use Mobil 1 Truck and SUV on my Jeep and it seems to work very well. I have heard about AMSOIL, and i think i am going to try it on my next intervel. Anyhow, leaks did arrise. Mostly from the Oil adapter housing, but i also changed the oil pan gasket and the valve cover gasket since A.) Im anal and just plainly wanted to replace them and B.) when oil leaks from that adapter housing it seems like its coming from just about every where. Some even mistake that its coming from the main seal (Which i also replaced and i would recommend replacing if you change your oil pan gasket. Dont forget to get the gasket that goes between your oil pump and the block (which i forgot) since the oil pump has to be removed to get the oil pan all the way out.)

From what i understand (and i could definetely be wrong) Synthetic is not only thinner but it contains more detergents then conventional oil. With that being said if oil has collected around a seal, it more likely then not will be broken up by the detergent. Sometimes this old oil is the only thing keeping the seal from leaking. Hence when it is removed leaks occur. So going back to what i was commenting about in the first place, i think the switch is well worth it not only to make the engine run better, but to help you find those nasty seals / gaskets that need to be replaced.
 
The high mileage oils were developed to help eliminate minor leaks from rubber seals. It worked great in my old 77 F250 with 368K miles on the clock.
 
when i switched my 89xj with 135k to mobil1 everything started to leak. i redid everything minus the timing cover, even did the oilpan twice.

now all i deal with is a slight seep at the oilpan.

stick with synthetic, its better for everything in the long run
 
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