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Switching Oils

Alan Haley and others have started this discussion on the CJ-3B Bulletin Board from time to time: "I need to change the oil again in my 3B and would like to use a 10-40 or so in place of the straight 30 weight that I have in there now. Some people have told me that an engine that grew up on straight weight oils ought to stay that way, others say there is no problem in switching oils. Anybody have a strong opinion on the subject?"

Jorge Hedges: "I don't see why you couldn't switch. What I did when I first bought my Jeep was pour in a can of engine flush, run it for about 15 minutes, and change the oil with 20W-50, substituting 1 quart with Slick 50. I have had no problems whatsoever, and, having a bit more viscosity, it helps if you have any slight leak (no hemorrhages)."

Oil panCurt: "This is a question which comes up often in old tractor circles. I think the prevailing thought right now is that today's oils are so much better than those of yesteryear that anything is an improvement. For my part my 1952 Farmall Super M is running mostly 10-30 detergent oil now. This came about because my wife used some of the 30W non-detergent that was supposed to go into the tractor in the lawnmower. During the next oil change I'll be dropping the oil pan to scrape out the sludge that has probably built up due to non-detergent oil being used in the engine.

"As for wanting to use 10-40, I used to drive an '88 GMC S-15 with the little 2.8 V6. That engine called for 5-30 but in the summertime I used 10-40 exclusively. This was because with 5-30 the engine leaked a quart every thousand miles; with 10-40 it leaked a quart every oil change. In the fall as the weather got colder the engine would tell me through a subtle change in startup sound when it was time to go back to the 5-30.

"So for some summer running I'd say sure go with your 10-40, but remember come winter 10-30 is probably a better choice and when it's very cold you're better off staying inside with a nice cup of hot chocolate -- but if you must go out and must drive your Jeep 5-30 is the way to go."

Cor Streutjens: "I own a Nekaf powered by the Hurricane engine. Since 1956 it has been lubricated by single grade W30 oil and I wondered why the stuff was used in the engine to this day. Before I bought the Jeep I knew virtually nothing about cars so I investigated. My humble opinion based on discussions with professionals and veteran owners: stick to the oil used in the time the engine was designed unless the thing is taken apart and revised to modern tolerances. Then you can safely use multigrade oil. Otherwise the engine can develop oil leaks, and (this was crucial to me) modern oils (or rather, the dopes in) tend to clean the insides too much and as a result sludge, residue from the single grade oil, can block oil passages inside meant to have the oil cool inner parts. If that happens you will wish you had never changed to modern oil. So I still use the good old single grade W30 -- no problem in winter over here, winters are not so cold (knock on wood). An extra oil change never hurts (the Jeep that is). When the time comes that I have to pull the engine and have the chance to clean it thoroughly inside and out I will switch but now I'd rather not."

Rus Curtis: "I was told many years ago to use straight 30wt. on a rebuilt engine until broken-in, 1K-2K miles. Then only after break-in switch over to multiviscosity."

Chuck DeHut: "My engine rebuilder also suggested 30 wt. for break-in up to 500 miles. Then 10W-40 for summer and 10W-30 winter. I live in the desert where temps hit 110F regularly -- I think I got the summer/winter thing right but others can input."

Ron Partch: "Chuck is right on the money, as for the break in 30wt for 500 miles. One thing: with air temp over 100F you might want to run a 20W-50. It depends on your weather -- I live in Colorado in the mountains, where an average temp during winter is 5F so I try to run a 5W-20."

Rus Curtis: "The answer to your question is, it depends. Where do you live? Does it get cold?

1963 Owners ManualRus pointed out that the Owner's Manual includes oil recommendations for different temperatures, which changed between the early and late editions.

1957 Manual
Above 90F (32C) SAE 30
Above 32F (0C) SAE 20 or 20W
Above 10F (-12C) SAE 20W
Above -10F (-23C) SAE 10W
Below -10F SAE 5W or SAE 10 plus 10% kerosene
1963 Manual
Above 32F (0C) SAE 30 or 10W-30
Above 10F (-12C) SAE 20, 20W, 10W-30 or 10W-20
Above -10F (-23C) SAE 10W, 10W-30 or 10W-20
Below -10F (-23C) SAE 5W or 5W-20

"My thoughts are 30 wt. would be okay for most circumstances. The multigrade 10W-30 should give you better starting performance in cold weather."

Synthetic Oil

Dave wondered: "Is there any problem using synthetic oil in a '54 CJ-3B?"

Chuck: "My experience with the syntec in our '54 resulted in pools of oil all over the yard. I replaced the oil seals front and rear but it didn't stop leaking completely (minus dribs and drabs) till I reverted to 10-40. Funny thing was that the M38A1 loved the stuff although it too started dripping more regularly. Our '56 has always used SAE30 0r 40 and sometimes 5 or 10W-30 or 40 with no loss of fluids to date."

Gale: "To my knowledge, the only advantage to synthetic oil is a longer useful life. Since we have to change the oil more often in our Jeeps due to a poor filtration system, its seems like a waste of money to pay three times as much for the stuff."

Ed Wilson: "I use synthetic gear oil (Amsoil 75-90) in all the gear boxes including the steering box. But I have yet to understand the advantage of synthetic motor oil. Dirty oil is dirty oil and if you change it on a regular basis, the synthetic is just more expensive. The oil in my '54 gets blacker than a Halloween cat in a few hundred miles and I probably change oil every 1000 miles or so. No modern motor oil is going to go bad soon with the temperatures and loads of a Jeep 4 cyl. If you want to use the synthetic, it won't hurt a thing except your pocket book. BTW, I use Kendall GT 30 HD."

Andy Stock: "My rule: If it wasn't around (or common) when the car was built and does not result in a significant gain (power or efficiency) for the money you pay, you probably don't need it. Synthetic oil, radial tires, fancy stereos, cell phones, etc. all fall into this category."

Bryan: "You need to change your oil for two main reasons: 1) dirt load and 2) the oil itself has broken down -- viscosity too low, high levels of oxidation, etc.

"Synthetic oil will extend oil life with regards to #2 only. If your oil gets dirty, synthetics don't help. If it stays clean, you can go longer between changes. 3B's have a poor filtration system, so dirt load will force oil changes before the oil just plain wears out. In that case, synthetics don't make much sense.

"Now, synthetic gear lubes are another thing, and would be a benefit to extend gear and bearing life in the drive train."

The Evolution of Engine Oil

Here are some excerpts from "The Evolution of Engine Oil: a few things you should know", by Dennis M. Vieira. Thanks to Patrick Watters for pointing out the potential significance of this subject to older Jeep engines:

For the past year and a half, I have noticed a sharp increase in worn rocker arms, lifters, and camshafts. I have replaced more rocker arm assemblies than ever before. It has become so prevalent, that I resolved to do some digging.

My research turned up some startling details: In 2004, the government mandated motor companies to warrantee catalytic converters for 120,000 miles. This forced engine oil manufacturers to remove most of the zinc and manganese from their engine oil. Coincidentally, those two substances happen to form the basis for the anti-scuff properties found in most engine oil.

Motor vehicle manufacturers counteracted this problem by changing the metal to metal contact of rocker arm feet and lifters to a newer style "roller rocker" and "roller lifter" arrangement. As you guessed, our antiques don't have "roller" technology and have only one way to deal with this change of oil formulation; dramatically increased wear at the rocker arms, lifters and camshafts; unless we change some of our maintenance habits.

In your antique car engine, you have lifters that ride directly on the lobes of the camshaft. Similarly, your rocker arms ride directly on the top of the valve stems. Good anti-scuff additives in oil are essential in preventing premature wear in classic car engines with older designs like this.

Rotella TSo What Can We Do? Oils designed for diesel trucks and racing gasoline engine applications have the highest amounts of zinc phosphate in them. Based on everything I have read, and tech articles from reliable sources like Comp Cams, I would strongly recommend the use of something like Shell Rotella "T" 15-40 engine oil in older vehicles.

As of November 28th 2005, Comp Cams has recommended the use of Shell Rotella "T" diesel engine oil during camshaft break-in and through the life of the engine. They also recommend the use of their camshaft break-in lube, part number 159, which has high concentrations of the aforementioned anti-scuff additives. Lately, they have been recommending the use of their camshaft break-in additive throughout the life of the engine!

Evidently, Oils formulated specifically for Diesel Engines and those called "Racing" Oils still contain the traditional concentrations of Zinc and Manganese that we need to maintain a healthy wear characteristics in our non- roller equipped engines.

Excerpt from the web site of Shell Oil:

"Shell Rotella-T Multigrade SAE 15W-40 is Shell's highest quality mixed-fleet heavy-duty engine oil. It meets the warranty and service requirements of virtually all diesel and gasoline engine manufacturers that recommend a multigrade oil. Rotella-T Multigrade exceeds the requirements of both cleaner-burning new engines and earlier models. Shell's unique chemistry helps ensure that the oil stays in grade in all seasons and under all types of loads."

Ironically, I spoke to a few restoration shops around the country that I am in regular contact with, who wondered why I am so intent on informing people about the latest engine oil changes. You see... these kinds of engine oil changes are good for their engine rebuilding business! They'd rather get paid to rebuild your engine, than tell you how to avoid needing their services!


Thanks to Dennis Vieira, to Dane R. Marley for the oil pan photo, and to all the other contributors. -- Derek Redmond

Also on CJ3B.info, see Oil Filters for the CJ-3B and Oil Pressure Tech Tips.

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Last updated 1 January 2007 by Derek Redmond redmond@cj3b.info
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