The point is that there is absolutely no data to substantiate any testimonial. The only solid facts are:
1: the 4.0 is a "dirty" overbuilt engine with similar characteristics of a diesel or industrial engine.
2: High zinc/phosphorous oil with a strong detergent package (diesel/fleet oil) has a SLIGHT edge over non-diesel oil.
3. The AMC sixes have had a solid history of 200k and beyond with every API certified oil on the market.

 

does anyone have the actual build specs of a 4.0? bearing clearances ring tolerances ? you guys treat this engine like it's a crude built pos. I highly doubt those numbers are any different than say most any other engine from the late 90s.

 

Post #196 and 197:
You're both retarded...
It's not we think this is a pos engine, we know this is a damn fine engine, plenty of low torque, good horsepower and longitivtiy, but just because it has those doesn't mean we take it for granted and beat the **** out of it, no we treat it right so that is does last for ever. It's like the Dana 30, you know it's a tough little axle, can stand quite a bit of abuse, but why not add some gussets, stronger shafts just to be sure it doesn't fail sooner.

 

At 230,000 miles I use rotella 15w-40 Wix oil filter change it every 3000 but it has has low pressure only at idol I think it's case it's so d*** good that it's restricting flow. but pulls my 32s just fine so don't say it's a POS motor cause honest I run the s*** out of mine and it's still runnin excellent

 

Which filter are you running? OE style or oversized?

I spun on a 51459 and have been amazed with how it behaves with 5w40 at -17C.

 

I'm pretty sure that it is the oversized one and it has made a difference. I think so anyway. Naw when I changed my oil last I also changed the trans, diffs oil and put a k&n air filter, oh also fuel filter and all of it just made it come to life. It seemed sluggish before but now it has more power than i could of hoped for

 

I try to use valvoline products. I use just about any filter other than Fram. Right now I have a Diesel engine till it gets warmed up. Some of that could be that the oil needs to be changed. I may go with another round of Rotella. I use a Motorcraft FL 1A ford filter. It's extended longer than a stocker, and has good filtering properties.

 

Be careful with "anything other than Fram".

Motorcraft is okay, but there are a ton of other POS oil filters out there. Can't go wrong with Wix or Napa Gold.

 

Their are plenty of fram filters with other names on them. Frams parent co is http://www.rankgroup.co.nz/. I use mobile 1 or royal purple with a mobile 1 rp wix or other good filter in everything I own. The 4.0 is a great engine and will be dependable with any regular changed oil. But a good synthetic in the proper viscosity will give better starts, less wear, better fuel economy and lower running temps. Why would anyone ignore these benefits?

 

That's good oil & so is the Delo 400 15w40

 

I changed my oil and tranny fluid just yesterday. This time, I thought that I'd try the Rotella T (15w-40). I have been using the Mopar filter but this time I thought I'd go with a Wix. My local Napa was closed, so I went by O'riley's to pick one up and they were out of stock in the 51515, so I got a 51515R (racing - supposed to be for racing and off-road use). I had never seen one of these so I'll let everyone know as time goes on how it seems to work.

 

My XJ oil pressure gauge will drop to 0 occasionally when playing offroad. This is with a Wix/Napa Gold filter and Mobil 1 5w30. I think it's the sender, engine runs damn fine and smooth still when it happens

 

YES! and so is walmart ST 15-40 diesel/fleet/industrial oil. My 4.0 had only 4psi when I bought her so I used ST to save $$. Now 30k miles later the sludge under the valve cover is completely gone. Still only 4psi but runs like new and I am on a quest to see how long this thing will last.

 

Just had a thought.

Sam's Club carries Rotella.

Wonder if there's a deal between Shell and Walmart using Rotella as their "store brand"?

The results you describe fit Rotella to a "T". Pun intended.

 

VERY bad idea! WIX's racing filters don't actually filter. They are extremely low efficiency and let massive chunks through. This is from WIX technical support. The 51515R has a nominal rating of 60 microns. The Jeep 4.0L requires at an absolute minimum nominal 25.

The ****head at O'Reilly should NOT have sold that to you. If I were you I'd go back and try to get a proper filter for free. Using that filter can and will cause damage to your engine. Have the store manager phone WIX and ask if you should be running it if he doesn't believe you. http://www.wixfilters.com/ContactUS.aspx