Synthetic, Blend, or Conventional Oil?

rasband

LJR Junkie
Supporting Member
Sep 11, 2018
342
256
Denver, CO
#1
What oil is best for our TJs? Is there a recommended filter? Are there differences for the 4L vs the 4 banger? Do we go for high mileage, if so, when?

I’ve not seen any definitive threads on the topic and thought it could be helpful to have a single spot to discuss/recommend.
 
Dec 6, 2018
46
15
Michigan
#2
What oil is best for our TJs? Is there a recommended filter? Are there differences for the 4L vs the 4 banger? Do we go for high mileage, if so, when?

I’ve not seen any definitive threads on the topic and thought it could be helpful to have a single spot to discuss/recommend.
The PO used Mobile 1 High Mileage Full Synthetic in mine. 10W-30. I will stick with synthetic, not sure on full or blended though.
 

zip04

TJ Enthusiast
Apr 14, 2016
261
240
#5
And to add to this. I am typically very picky with my oil. I have run amsoil in my Harley’s and previous vehicles for years. It is simply unnecessary in a TJ.
 
Likes: StG58
Jun 1, 2018
37
30
Atlanta, GA
#8
Both our 4.0s had a slight rear main seal leak. I've been using Mobil 1 European Formula 0W40 and the leak is down to minor sweating. Also no more lifter tap during start-up.
 

superduty

TJ Enthusiast
Apr 7, 2016
136
82
So Cal
#9
I don't think you will find a definitive thread on this subject. There is no definitive answer that everybody will agree upon.

That said, I can't say I've ever seen an engine that has failed directly as a result of using regular oil, blend or synthetic oil.

Changing your oil and filter on a regular basis is really the most important.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

pcoplin

TJ Enthusiast
Supporting Member
Dec 1, 2018
111
119
Santiam, OR
#10
Valvoline or Napa oil for the Jeep and Mopar V8s is all I ran.

In my higher performance engines I use full synthetic.

Sent from my Pixel 3 XL using Tapatalk
 

Mr. Bills

TJ Enthusiast
Nov 24, 2017
793
1,009
Area Code 530
#11
The Factory Service Manual calls for 10w30 motor oil in most climates. It does not differentiate between conventional, synthetic blend or full synthetic which means that any of the three can be used.

The Factory Service Manual also calls for an oil and filter change every 3,000 miles for "Schedule B" usage, which includes stop and go driving, offroading, driving in dusty conditions, trailer towing, etc. Many of us extend the service interval to 5,000 miles and even longer for full synthetic oil. Use any name brand filter of the correct size - even the orange one will be okay if you consistently change your oil at the shorter 3,000 mile interval.

I use Valvoline Maxlife synthetic blend 10w30 with a Fram P/N TG16 Tough Guard filter and change the oil every 5,000 miles.
 
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Likes: rasband

Mr. Bills

TJ Enthusiast
Nov 24, 2017
793
1,009
Area Code 530
#14
Fram Tough Guard TG16

Edit:

I'm going to add to this post to give some context to the tangential discussion below regarding whether there is any advantage to running a filter longer than the filter specified by the manufacturer.

Back in the dinosaur age when CJ-7's with the 258 c.i. I-6 and smog exempt diesel pickups freely roamed the earth it was not uncommon for we cavemen to use a filter with similar specs as the OEM filter but a few inches longer. Typically the cost was the same or very nearly the same. The justification for deviating from stock was that the additional oil capacity and larger filtration area was a potential benefit that came at no additional cost. Whether the benefit was real or imagined was largely immaterial; we were simply getting the best bang for the buck.

The only reason I don't use the longer TG8A filter is that the manufacturer specified TG16 is quicker and easier to maneuver into place and I place a higher value on convenience than when I was younger.

And now back to our regular programming.
 
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jwrangler187

Member
Supporting Member
Dec 30, 2018
61
39
hilton ny
#20
Never EVER run full synthetic for the first time on a high milage engine. It will clean everything up and u will find leaks in seals that were once gunked up and not leaking before.

Had to replace my oil pan gasket because of that. The synthetic is also thinner so it will leak faster