20W50 harley oil in a sophisticated tractor motor.........really? If seals r bad, any oil will leak. We've been running synthetic for 4 1/2 years now......still dry as bone underneath.

 

Don't be starting that tractor motor ****......

 

SAE oil viscosities are ranges that overlap slightly. A "thick" heavy duty diesel 5w-30 oil can actually be a little thicker than a "thin" 0w-40 gas engine oil. I've used synthetic HDEO 5w-40 in my Jeep for years. Synthetic oils could cause additional leaks or worsen existing leaks or not. They will improve oil flow particularly in cold temperatures.

 

Update: I decided to go ahead and try the Mobil1 10w-30 full synthetic, So far so good. it has even made the engine a bit quieter. I'll probably be switching back to conventional after a few thousand miles. Is Mobil super the conventional oil from Mobil? I also saw a Mobil 5000??? Like I said I've always used plain yellow bottle Pennzoil so I don't know much about other brands.

 

......the store didn't have 0W30 or 5W30 M1?

 

No 0w-30 but I did see 5w-30. I like to stay with what the manual recommends which is why I went with the 10w-30.

 

Does anyone know if Mobil super or the Mobil 5000 is Mobil's conventional oils or are they some sort of blend? I'm pretty certain that the Mobil 5000 is their base conventional oil but just want to be sure.

 

Don't use Mobil 5000 unless you're on your way to the auction to get rid of your Jeep.

Mobil 1 10W-30 and a Wix filter FTW.

Owner's manual says 5W-30 is only used if maximum temps before the next oil change won't exceed 60 degrees F. So there.

 

.......and how old/out dated is that manual?

 

Doesn't matter. Our Jeeps are old/outdated anyway.

 

Doesn't matter. The oil on the shelves isn't as old as our Jeeps. Oil had changed a lot in the last 20 years.

Late model 4.0L manuals specify 5w30 as preferred for all temps.

 

I think 5000 is discontinued. Super is their cheapo dino juice.

 

.....by all means, stick with using old/outdated oil......but u might have trouble finding it. If the bottles of old oil r covered with dust and spiderwebs, should be good to go.

 

Garage sales and estate sales. Sometimes in the old round cans. And, the old dude probably left one or two of those spouts LOL.

 

Excellent, I forgot about looking at garage/estate sales.......maybe those dudes at Antique Archeology/American Pickers have a case or two of obsolete SF, SG, SH rated tractor motor oil.