Wow should try some gear oil in it. she'll run like vette then.

 

there is no such thing as an inline v6.

 

I'm sure it will. But hard to argue with the fact that all those 4.0s out there with hundreds of thousands of miles did just fine using those oils.

 

They were not exactly designed with super-tight tolerances, low tension rings and a host of other "modern" features, lol.

 

Thanks Radi. My thoughts exactly. No hydraulic lash adjusters, roller lifters, aluminum heads and blocks, and squeezing large amounts of horsepower out of small displacement.

While all this oil 101 stuff may be applicable to today's modern engines, and that knowledge critical to their longevity, our trust old 4.0s do fine with what was recommended for them.

The biggest killer to 4.0s was and is the use of poor quality oil filters with faulty anti-drainback valves. Due to the odd upside-down and sideways mounting of oil filters on our 4.0s, a good quality oil filter has been critical.

 

We have an old owners manual that will never be re-written but a safe bet would be that IF it were re-written today, the recommended oil weight(s) would change. I'd be willing to bet, if Jeep/Chrysler could get away with it today, they would say "must use 0W30 oil". What engine manufacturer wouldn't insist upon using a 0WXX oil (if they could get away with it). All 0WXX oils are synthetic. In '89, 0WXX weight oil wasn't even referenced in the manual because it hadn't been commercially refined yet.

If one is going to "stick by the book", then one may need to park a '89 XJ because the '89 manual calls for API "SF" rated oil. "SF" oil hasn't even been available on the shelf for 20+ years, neither has "SG" or "SH" rated oils which are both successors to "SF" rated oil.

From the 101 stuff......"It is time to introduce the concept of lubrication. Most believe that pressure = lubrication. This is false. Flow = lubrication. If pressure was the thing that somehow lubricated your engine then we would all be using 90 weight oil. Lubrication is used to separate moving parts, to keep them from touching. There is a one to one relationship between flow and separation. If you double the flow you will double the separation pressure in a bearing. The pressure at the bearing entrance is irrelevant." by Dr. A E Haas

I don't think anybody is saying that 20W50 will kill a motor quickly (works in Harley's ).....but the fact is, thick oil flows slower thus less/slower flow = less lubrication. Dr. Haas is trying to explain away the thick oil myths/misconceptions/old school thinking with fact, reasoning and scientific proof.

We're all friends here and we all need to realize that things/times have changed/progressed over the years......including motor oil. As time has advanced, automotive manufacturers have requested that lighter motor oils be refined for use in there engines. Increased fuel economy is just one of the many reasons. All else being equal, if thinner oil (not thicker oil) slightly increases fuel economy (which it does), that must mean more of X amount of power is being transmitted to the wheel and less to the oil pump, which equates to better/increased performance. Warranties and engine life have increased over the years, not decreased. Lighter weight motor oils is not the sole factor for this but lighter weight oils certainly aren't causing increased engine failures.

Owner neglect kills XJs, not modern/lighter motor oils........KEEP RAISING THOSE HOODS.

 

Interesting:

http://www.volvoclub.org.uk/oil_school.shtml

 

EXCELLENT!!! Pressure serves no function other then to let you know you have a mechanical issue. If you are getting flow to the top of the cylinder head that is a good indication that all the oil galleries are full...oil will then flow even at 0 psi by gravity to the mains and crankshaft cross passages to the rod bearings. A worn engine will rattle for a few seconds when first started in the morning because the oil has drained off of the journals. Once oil has FLOWED to the journals the rattle subsides. There is oil pressure in a bearing but it is created by the elliptical movement of the rod to create a wedge of oil on the leading edge of rotation. This pressure can reach thousands of psi.

 

I believe Castrol "dumbed down" the original meaning/definition of "synthetic oil" with their concoction of synthetic oil.

From the Amsoil site.......
In the past, it was always believed that purchasing a synthetic oil meant just that, you were buying an oil that was man made rather than a petroleum that was pumped out of the ground. Towards the end of the 1990s this all changed with the reformulation of Castrol Syntec. They had changed their formula from a PAO base stock, which was one of the most commonly used base stocks at the time, to a petroleum base that had gone through a process called Hydrocracking. This process refines the oil very well, to a point that Castrol called it a Synthetic. While doing some testing Mobil discovered the formula change and took Castrol to court claiming that they were false advertising the oil as a Synthetic, since it's base stock was made from a petroleum. Mobil's stand basically said that a "synthetic" oil is something man made in a lab to certain specification that cannot be found in nature that way, which was the common thought even consumers had at the time. Castrol's stand was that this process the oil went through was so refined that it no longer resembled anything in nature, therefore it was a "synthetic." Because the API couldn't come up with a good definition of a synthetic themselves, they accepted Castrol's definition.

 

I started reading Motor Oil 101 and made it through to 108 before I went back to huffing PB Blaster. Very interesting stuff, especially how multigrade is achieved in mineral oils! Hilarious. I'm surprised that manuals don't have multiple service schedules that include very short commutes. If my engine was brand new it'd make sense to run 5W20 as often times the engine's only been up to temp for a minute or two by the time I get to work. But then I'd have to swap it out for something heavier every time I went on a trip... Makes me wonder about using the block heater more frequently.

 

Some manuals do have 2 maintenance schedules........normal and severe service. Short trips, motor not fully warming up fall under severe service schedule.

 

Indeed, mine has two, however the oil weight has nothing to do with it. It lumps desert climate, towing, and short city trips together, just specifying a lesser oil change interval and more grease pumped into the chassis lol. Long haul desert driving and towing are the opposite of a 5 minute commute in terms of oil warming up

 

Glad that's been cleared up........there may have been some confusion between night and day.

 

I don't doubt it. My horizontally-opposed inline V8 picked up at least 25hp with SAE60.

 

Lmao.

Heh, indeed