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what's the thickest oil weight to run?

muddeprived

NAXJA Forum User
Location
PA
I got a rear main seal leak. It gets kinda bad when i'm cruising on the freeway at 65 mph and whenever the jeep is warmed up. I have a trail ride coming up this weekend and don't have time to fix the seal so I'm thinking of running thicker oil just until I can fix it next week or so. What's the thickest engine oil I can run in the jeep to maybe reduce the leak? Is there any quality additives I can toss in there to reduce it?

I run 5w-30 year round.
 
Put in about a cup of lacquer thinner in the oil. It will soften and swell the seals. There are off the shelf additives available as well, but they use the same stuff/concept.
 
The first # is the cold viscosity (thickness at startup)
The second # is the hot viscosity (running temp thickness)

15w40 is not much thicker than 5w30 when warmed up
 
When I worked parts I saw a couple guys try to fix a leak in their ford van with 80-140 gear oil. They dumped 6 quarts in and actually made it to the end of the parking lot before the truck quit for good.


15-40 diesel like Rotella is a good choice, and about as thick as I would go. At one point you will start to tax your pump's abilities to push it through the passageways, and the oils ability to lubricate the bearings in the crank journals.
 
When I worked parts I saw a couple guys try to fix a leak in their ford van with 80-140 gear oil. They dumped 6 quarts in and actually made it to the end of the parking lot before the truck quit for good.


15-40 diesel like Rotella is a good choice, and about as thick as I would go. At one point you will start to tax your pump's abilities to push it through the passageways, and the oils ability to lubricate the bearings in the crank journals.

The thick oil won't be in there long enough to do any harm. It'll be out next week or so when I do the rear main.

Do you think Lucas oil stabilizer will help? I've been recommended this by a couple of people here and at the shop. They said it works well in reducing leaks.
 
Thanks guys. What about 20w-50? I saw this available with all the other oil weights. That should be thicker.

I used it in my old rig with 220k on the clock. Still ran great without any more excess leaks or smoke at 240k.

During the winter id use 10w-30 though, but if you live in an always warm climate I wouldnt worry about it.
 
5w50 would be awesome ;)
 
I like the lucas oil stabilizer. Some people blast it, and try to cite some testing sites, but from what i have seen most of the sites blasting it are running biased or false tests, and are funded by a major competitor.
 
I currently run 20w-50, she purrs like a kitten.
 
When I worked parts I saw a couple guys try to fix a leak in their ford van with 80-140 gear oil. They dumped 6 quarts in and actually made it to the end of the parking lot before the truck quit for good.

It motor oil terms thats more like a 40W-60 motor oil. Hot would have probably been okay, but they probably pretzeled the oil pump shaft trying to pump that cold.
 
It motor oil terms thats more like a 40W-60 motor oil. Hot would have probably been okay, but they probably pretzeled the oil pump shaft trying to pump that cold.

yea, especially in a van that had already been run ragged, on a cold day. It did make it to the end of the parking lot.
 
In my 1990 I ran 20w50 in the summer and 15w40 in the winter. Seemed to work and kept it together pretty well for several years. Sold it a while ago and the guy is still happily driving it around.
In my newer 1998 I run 5w30 and it feels much smoother (surprise surprise), but the thicker oil was keeping the old engine alive.
 
Thanks for the responses. I ended up going with 10w-40 and a bottle of lucas. There were thicker oils but not enough in stock unless it was $4 a bottle. I didn't want to spend a fortune on oil that's only gonna be in there for a week or two. I'm gonna fill her up and hopefully all my seal leaks will cure themselves and my odometer starts ticking backwards. I am ready to be amazed. LOL
 
It motor oil terms thats more like a 40W-60 motor oil. Hot would have probably been okay, but they probably pretzeled the oil pump shaft trying to pump that cold.
it would be thicker hot than cold
 
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