Synthetic Fluids for High Mileage XJ

D

desertred

NAXJA Forum User
Location
Along the Wet Mountains, CO
I'm looking to replace the tranny, T-case, and differential fluids on my 88 XJ with 198K. My question is if anyone has switched to synthetics at such a high mileage and did you experience and leaking seals with the switch? Would I be better suited at this point to stick with dino fluids (except for the T-case, which I know takes ATF) and limit the chance of leaking seals?
 
On the engine side alot is going to have to do with how dirty it is internally. I think I would initially go with a 50/50 mix of mobil 10w30 and mobil-1 10W30, dont' waste your money on the 'blends', mix it yourself, that way you know it's a 50/50 mix, none of the blends say 50/50. Then see what happens, it won't blow up or anything but the syn will start cleaning any sludge out thats in there so watch the dipstick. When it gets too dirty to read thru change the filter, do your normal oil changes too.
 
I switched to royal purple at 187K and have had no problems with leaks. Has a little valve tick but cant say that that is attributed to the oil change.

did the trans diffs and Tcase at the same time no problem
 
My concern is with everything BUT the engine. I installed a reman a couple of years ago and started with Mobil 1 10W30 right off the bat (still got the rear seal to start leaking a lot sooner than I had hoped). Now I'm tackling the rest of the driveline.

From my understanding, there used to be an issue with using synthetics with older seals. Either the syn was incompatible with material used to manufacture seals several years ago, or the cleaning additives in the syn would "wash" away the sludge that had built up around existing seals. As a result, leaks were prone to develope upon switching to synthetic oils. I don't know how old the seals are in the driveline (other than the engine). They have not been replaced since I bought my XJ four years and 40K miles ago.
 
i replaced all fluids w/ AMSOIL at 169,000. the axles really quieted down and the tranny shifts better. didnt change filter in tranny, but will soon at 180,000. i have no leeks and im getting 18-23mpg on highway w/ roof rack w/spare and 32" tires
 
A bit off topic, but for the engine, you can do much better in terms of wear metal control than Mobil 1 10W30. I've seen several used oil analyses with this oil and they show just about the highest rates of iron and lead wear.
For around $2/quart Havoine 10W30 has done much better than Mobil1, and for a bot more, Castrol has shown good results.
I know someone will pipe up and say how they got 200K with Mobil1 10W30, so it must be fine.
These engines will last a long time on most any oil, but some peform better than others.
 
I have an 86 Comanche with about 270K on it and I ran (Lived in South Florida) straight Valvoline 40 weight after about 190. My family business always ran straight weight oil in the work trucks and it worked for me. No bad leaks and it never left me stranded. I would say for you run a higher final grade oil or go to the synth (it gets cold were you live)...IMO. That was highschool so I also beat the crap out of it..hahaha
 
you'll be fine, I don't know of any concerns when switching axles and t-case to synthetic. I have heard unconfirmed stories of transmission destruction by changing fluid for the first time at 100k, but no issues with switching to synth in a well maintained aw4.
 
ahm said:
i replaced all fluids w/ AMSOIL at 169,000. the axles really quieted down and the tranny shifts better. didnt change filter in tranny, but will soon at 180,000. i have no leeks and im getting 18-23mpg on highway w/ roof rack w/spare and 32" tires
Click to expand...

what gears, tail wind?, gutted her like a sinking pirate ship?!?! :piratefla

please elaborate :idea:

thanks
 
mikeny59 said:
what gears, tail wind?, gutted her like a sinking pirate ship?!?! :piratefla

please elaborate :idea:

thanks
Click to expand...

Long Island and NYC do not measure in miles per gallon, they measure in gallons per hour, generally at idle or a slow crawl. :D
 
Yeah, but our terrain is so flat,,,,,,,,,,,,,,,:laugh3:
 
gears- 3.55(want 4.10), wind ??, have only added stuff, but i dont drive w/ what i dont need.
work nights, not much crawlin. drivin slow makes a big difference in mileage(-)
 
I'd continue to use dino oil. With that many miles using a thinner synthetic oil will increase your chances of leaks. synthetics work better in tight engines. Before I change my oil I drail about a quart out of the pan then put a quart of ATF in the oil and run it for a few miles. The detergents in the ATF clean some of the crud out of your engine and will help it run better. It won't hurt anything because the ATF provides protection agains friction as well.
 
camarors8992 said:
I'd continue to use dino oil. With that many miles using a thinner synthetic oil will increase your chances of leaks. synthetics work better in tight engines. Before I change my oil I drail about a quart out of the pan then put a quart of ATF in the oil and run it for a few miles. The detergents in the ATF clean some of the crud out of your engine and will help it run better. It won't hurt anything because the ATF provides protection agains friction as well.
Click to expand...

The synthetic wont increase your chance of leaks. If the motor leaks after the change, it leaked before. Just that it had crud built up and wasn't showing. Me personally, I'd rather know I had the leaks so I could fix them rather than not.

Sarge
 
HE SAID HE WASNT WORRIED ABOUT HIS ENGINE!

I'm looking to replace the tranny, T-case, and differential fluids on my 88 XJ with 198K
Click to expand...

My concern is with everything BUT the engine. I installed a reman a couple of years ago and started with Mobil 1 10W30 right off the bat (still got the rear seal to start leaking a lot sooner than I had hoped). Now I'm tackling the rest of the driveline.
Click to expand...

Please read before posting.
 
mikeny59 said:
Yeah, but our terrain is so flat,,,,,,,,,,,,,,,:laugh3:
Click to expand...

...even thinking about going to 3.07's w/my 31's, the lower the idle, the better the mileage, I think someone said that in a Dukes of Hazzard episode. :farmer:

Anyone other than Rich ever hear of the LIE here on LI, NY?!?

Seriously, the only real experience I can impart is that last week I replaced the wheel bearings in my '98's 8.25 (pix and some very interesting tips to follow), had changed over from dino at 3k, now at 117k.

Mainly, well, did it soley as preventive maintenance, changed out the mobil one dif fluid three times prior, absolutely no leaks from the seals, and the ring teeth were so darn sharp, as edgy as the day I first saw 'em at 3k. And the pinion yoke seal is as dry as a bone, even after a I broke the rear u-joint (took pinion yoke w/it) and the *master mechanic* I was at the mercy of bashed the old pinion yoke off with a baby sledge and impacted back on to pluto and beyond the new yoke w/o any knowledge of crush sleeves or preload. Or even a tad of grease in the old seal...

:guitar: why a guitar, i dont know, i just don't :tears:
 
Myth #1: Synthetic motor oils damage seals.

Untrue. It would be foolhardy for lubricant manufacturers to build a product that is incompatible with seals. The composition of seals presents problems that both petroleum oils and synthetics must overcome. Made from elastomers, seals are inherently difficult to standardize.

Ultimately it is the additive mix in the oil that counts. Additives to control seal swell, shrinkage and hardening are required, whether it be a synthetic or petroleum product that is being produced.
Click to expand...

http://www.synthetic-oil-tech.com/d.cgi/1218983/articles/ten_myths_about_synthetic_lubrication.htm
 
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