cruiser54

You and a gagillion others!!

Why is it that those of you who HAVEN'T done something are telling us that HAVE done something, that it doesn't work the way we have experienced by actually HAVING done it?

sycoglitch

Wait, so you have real life experience with jeeps. :mind blown:

cruiser54

Only from reading books and interweb forums.....

mschi772

The hardest thing to believe is that someone as knowledgeable and helpful as Cruiser was once a dealership service dept employee. I can't wrap my head around the concept of a dealership having someone so useful working for them.

bigbadon

^^^^BINGO^^^^^ The 4.0 is a 50 year old engine with the same bearing clearances it started out with.. Newer overhead cam and tighter tolerances engines are built around the government mandate for higher efficiency oil weights. Oil has also been modified over the years for the same reasons. You will not find any commercial truck fleet that runs 5-30. Jeep's recommendation on newer 4.0s for 5-30 is coming from the Feds. The wifes tale about not getting oil flow on a cold day is somewhat true for an overhead cam engine but as dmill said "the 4.0 isn't exactly picky when it comes to oil".

Fred/N0AZZ

Most of the reason behind the 0w ad 5w weights were to meet the Federal Emission ****'s.

sycoglitch

Yup.

salad

Let's clear up a few things here...

1. The number before the W is a viscosity determined by a few tests. It has two uses: cold cranking thickness, as in 20w anything is too god damn thick at -20, and initial startup wear. Engine lubrication is provided by a FLOW of oil from the pump. Too thick and there's no flow. This is bad for lubrication. I'm a fan of 40-weight diesel oils in the 4.0L for a number of reasons. The largest argument AGAINST doing that is so many people run 15w40 when they really shouldn't and don't drive their vehicle any differently than if it had 5w30 in it. The difference is that bearings in the engine are starved of oil during startup. This is shown by an increase in bearing material in used oil analyses. This is not an opinion, but a favt derived from scientific tests. The oil industry gave us decent multigrades many years ago. Enjoy the modern convenience. After all, you're using a computer right now, probably have indoor plumbing, too!

2. The 4.0L is very similar to industrial engines found out in the wild (fun fact: Ford still sells their 300ci inline 6 in the marine and industrial markets) but it is NOT a diesel. It's not even a Toro-Flo like another well-educated poster put lol. There are a lot of differences in design including no turbo, no oil cooler, sump capacity is vastly less, all of the clearances are looser, forces from the piston are less, oil is polluted differently, etc.

3. The larger difference is that a 4.0L is not driven like a diesel engine. Most users are not accustomed to a MANDATORY warmup period. This alone gets you to running an oil like 15w40. Smaller diesels like the Cruze and TDI only take 0w40 these days so you can't look there. Heavy trucks also have massive oil sumps so there is a major economic factor between replacing 10 gallons of conventional vs 10 gallons of synthetic every few hundred hours. (depends on engine and driving of course). Anyway, most of these engines (until recently) are fired up and left running. Most 4.0L owners I know drive their Jeeps like cars and let them shut off. In the winter it's not uncommon to have to heat the sump of a big diesel to get it to crank... Block heater if you're lucky, charcoal or propane if you're not. You used to have to do this with card, too, before batteries and starters were better and most of the world ran monogrades SAE30 and SAE40. Most 4.0L owners I know are very happy to get out and just turn the key when it gets cold.

So my point is, there is a big difference between running a 15w when you should be running a 5w or 0w. Only some of it pertains to the engine. A fair bit is on the driver.

If you want more there's a thread in my signature that discusses engine oil.

sycoglitch

Stop giving real world facts. Aint no body got time for dat. Lol

Klutch

Thank you. I didn't think you were making it up. I just wondered if you were sourcing an actual Jeep owner's manual or something else. No need to accuse me of "Just throwing crap out there". What I wrote is based on more modern recommendations for oil. What you wrote is based on older recommendations for oil.


Are the changes all due to emissions and fuel economy? I don't know. Perhaps it's a combination of emissions, fuel economy and changes in engine oil.

bigbadon

check out page 2

http://www.apicj-4.org/EngineOilGuide2006.pdf

cruiser54

Now that's funny!!

You mean someone in management that actually works on vehicles and is an enthusiast?

If only others would realize that. That was a great part of our success.

cruiser54

Yep. Economy. Always self-serving stuff from vehicle manufacturers.

Followed up with a good dose of BS.

Metmknice

Basically like Wikipedia?

mschi772

Not just management. My favorite to this day is the mechanic that hung-up on me when I told him that I would not accept him slapping a new steering stabilizer on my XJ as satisfactory for dealing with a wobble issue. He made the diagnosis over the phone without ever even seeing it when I was scheduling an appointment to have it investigated (I just didn't have the time to deal with it then) and refused to believe that it could be anything else--told me outright that he KNEW he was right and wouldn't even poke around. As I'm sure you know, the stabilizer is basically never the sole cause, and in the end, my particular case happened to be a tire wear/balance issue.