Motor Oil

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Motor Oil

Post by CT Trooper » Mon Apr 16, 2012 7:14 pm

I have a 1954 M38A1. The engine has gone through a complete rebuild. All the mechanics to include the shop that rebuilt the engine recommend that I use 30W ND motor oil. What is the consensus of the forum?


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Re: Motor Oil

Post by artificer » Mon Apr 16, 2012 7:24 pm

If it is a new engine use a "run in oil" usually a straight 30 weight, then @ first change use a modern detergent oil e.g 5W40 Shell Rotella or Rimula from Walmart unless you want to pay too much
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
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Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Motor Oil

Post by Joe Gopan » Tue Apr 17, 2012 4:21 am

Best to stick with a straight SAE #30 Detergent Oil. The Jeep engine is a long stroke industrial type with clearances greater than modern engines. The OE#30 used by the Army in this engine has been Detergent Type since 1941.
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Re: Motor Oil

Post by SB5477 » Tue Apr 17, 2012 12:24 pm

Ben, the recommended oil type is not the non detergent kind, because of the filtering style?

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Re: Motor Oil

Post by artificer » Tue Apr 17, 2012 1:12 pm

This topic has been done to death many times.
Here is a quote from one of the best [real] mechanics who used to contribute here.
I will add SHELL ROTELLA as it still has additives incl zinc other oil brands have removed that help prevent scuffing of the valve/cam followers
Pete Silfven said: I'll add my 2 cents worth here, based on 40-odd years in the automotive business, of which 35 were spent with Ford R & D.

As was mentioned, engines don't really wear out anymore. There are several reasons for this. First and foremost is modern oils. They are so superior that I can't see why ANYONE [including Joel is added] would want to ever go back in time to what was available in 1945. Second is improved crankcase ventilation and higher engine operating temperatures. This means that condensation (water vapor) is rapidly boiled off before it has a chance to combine with oil to form sludge. Third is electronic engine control and fuel injection. This drastically reduces cylinder washdown and oil dilution from excess fuel, and reduces engine wear. Fourth is unleaded fuel. Because of it, spark plugs now last much longer, and with modern platinum types, 100K miles is not unusual. Combustion chamber deposits are no longer a problem.

We can apply some of this to our MVs today and make them live longer.

Oil - Use the best, latest, multiviscosity oil available. I don't think that synthetic is really necessary for most of us, because the oil really needs to be changed at least once a year before winter. Viscosity is not as important as some think, anything from 10W-30 to 20W-50 is OK. Change the filter cartridge at each oil change.

Crankcase ventilation - We are in pretty good shape here. Make sure the PCV valve is clean and assembled correctly. Make sure the associated lines and hoses are clear of sludge and open. Engine temperature is very important. Use a 180 degree thermostat and a 7psi pressure cap. This will help to boil off the water and acids from the oil and prevent sludging.

Fuel system - This is a real problem. Carter W-0 carburetors are a pretty Neanderthal design. The best that can be done is to make sure that it is set up to specs, both float level and metering rod. Check fuel pressure and correct it if necessary. Avoid overuse of the choke.

The point here is that although the type of oil is important, there are other things that need to be done to help the oil do its job, and to prolong the life of the engine.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Motor Oil

Post by Joe Gopan » Tue Apr 17, 2012 1:37 pm

I am not going back to the "dark ages" The Standard Oil for normal use in the US Army was OE-30 for the 1/4 Ton Trucks and nearly all the Water Cooled engines in MB/GPW, M-38-M-38A1 Jeeps and other Combat 4X4 6X6 trucks of the WWII period thru the late 60's. There is documentation in service bulletins and the verey informative WWII "ARMY MOTORS" that the motor Oil used in the WWII vehicles id "detergent oil". I have been servicing new Civilian Jeeps and Military Jeeps since the 50's and have seen the results of multiple viscosity oil in hundreds of Jeeps when driven at highway speeds, the engines wear out much sooner than Jeeps using SAE #30. Multiple viscosity was OK during the Dec thru Feb subfreezing period.
remember, the Army was the largest fleet operator of the MB/GPW thru M-38A1, there is a wealth of good maintenance knowledge to be gained from what the Army and engine performance experience gained from professional Civilian Jeep dealer experience.
My present oil of choice for my M-38A1 is Rotella T 15-40, and CCKW is Shell Rotella SAE 30,my MB has only had AMOCO Permalube 200 SAE #30H.D. since the GPW engine was installed NOS from a crate 40 years ago, I bought several cases and have enough for another decade.
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Re: Motor Oil

Post by Joe Gopan » Fri Dec 15, 2017 10:14 am

Have had a change of mind on the choice of Motor Oil for my MV's. I still have enough of the Permalube 200 SAE #30 HD for a while, but will replace it with LUBRIPLATE SUPER HD-5 SAE #30 HD. There have been many comments about the anti wear value of Motor Oils having "Zink" content. I have been reading the labels of oils that some claim to have zink. The only one I have found so far is the above named Lubriplate, "contains Fluid Zinc" is listed in the contents label.
Where does it say contains zinc on the Rotella T?
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Re: Motor Oil

Post by Cabin Fever » Fri Dec 15, 2017 11:07 am

I am by no means a mechanic, but I have been using Shell Rotella and ZDDPlus additive to my crankcase for the past five years. The ZDDPlus contains both zinc and phosphate which is no longer added to modern motor oils.

https://zddplus.com/zddp-information/
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Re: Motor Oil

Post by dpcd67 » Sat Dec 16, 2017 2:30 pm

I use only multi-viscosity oil, whatever brand is on sale, BUT, I add Lucas zinc additive to it. In all my MVs. And my 67 WM300, which is about as close to an MV as you can get.
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Re: Motor Oil

Post by W. Winget » Mon Dec 18, 2017 6:17 am

I would use Shell Rotella, Multi-vis. (I was a Penzoil user for years) Shell seems better and cheaper, especially the diesel turbo oil (If it can do diesel turbo fleet semi-tractors...for hundreds of thousands of miles.....it can do a 4 -8 cyl gas automotive engine...)

If you want me to DIG through the DTIC site for the Army testing of Multi-VIS VS Single oil, I can, but the bottom line to that study was using multi-vis was fine in military applications. (Here's the Synthetic multi-vis test): http://www.dtic.mil/dtic/tr/fulltext/u2/a081444.pdf
Only reason I would use NON-DETERGENT would be a non-filter equipped engine like my Clarkair CA-1 where it's a splash lube system and no filter to clean the oil. You simply change it more often to get the crud out.
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Re: Motor Oil

Post by Bill P » Fri Dec 22, 2017 4:13 pm

I use Valvoline VR1 Racing Oil SAE 30. It contains zinc and states on the container that it is appropriate for older flat tappit engines. I have a ‘54 M38a1 also.

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Re: Motor Oil

Post by Joe Gopan » Sat Dec 23, 2017 4:44 am

There is a bit more consumer confidence when the necessary ingredients are listed on the container. There was a time when Shell Rotella T 15W-40 was not compatible with certain make engines.
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Re: Motor Oil

Post by Cabin Fever » Wed Dec 27, 2017 12:03 pm

Bill P wrote:
Fri Dec 22, 2017 4:13 pm
I use Valvoline VR1 Racing Oil SAE 30. It contains zinc and states on the container that it is appropriate for older flat tappit engines. I have a ‘54 M38a1 also.
It's interesting to read that Valvoline adds ZDDP to the VR1 racing oil. As posted earlier, I add ZDDP myself at each oil change. Now, I'll have to figure which way is cheaper....buy oil with the ZDDP already added or do it myself. LOL!
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Re: Motor Oil

Post by 85jeepcj » Wed Dec 27, 2017 1:59 pm

Racing oil often lacks detergents, not a good oil for the willy engine, especially with the marginal oil filtration system.
Valvoline does explain this in its spec sheets

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Re: Motor Oil

Post by Joe Gopan » Mon Jan 01, 2018 12:47 pm

SHELL OIL CO. Engineer's quote regarding Shell Rotella T SAE 15W-40.
"The chemistry of the oil may not be compatible with the metallurgy of the engine components".
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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