1972 motor and modern oil?

[Jimmy C]

I have a 1972 Steyr Puch Pinzgauer and am wondering if I should be using old fashion or modern oil in it. It has a 4 cylinder 2.5 liter air-cooled engine producing about 95 HP. It has aluminum pistons in cast iron cylinders, flat tappets, and gear driven cam. The crankcase is vented but not ventilated. I have an oil temperature gauge and the oil tends to stay around 200F. There are no valve seals

The lack of true ventilation in the crankcase results in some water condensation. This is noticeable as “white gunk” in the oil fill pipe but is never noticeable in the oil itself.

I recently had the engine apart and it looks clean with no oil related issues other than hardening of the 50 year old seals on the pushrod tubes.

The manufacturer in 1972 specified SAE10 in “winter” and SAE 30 in “summer”, both meeting MIL-L-2104B. Oil pan holds about 7 quarts. Specified oil change interval is 3,000 miles/100 hours.

Oil chat among owners has several themes. One is that changes to oil additive package to be catalytic converter friendly (reduction of ZDDP) makes newer oils inappropriate. Another is that synthetic oils cause more problems with oil fouling of plugs than mineral oils. A fair number of owners use an SAE 30 HDEO rated for compression but not spark engines.

.best regards,

Jimmy C

 

[Astro14]

People believe weird things, and when others believe those same things, it becomes self-reinforcing.

Most of your engine doesn’t care about ZDDP, it’s really just for the cam lobes, part of why my 1932 engine has roller cams - oil wasn’t very good back then.

In a 95 HP engine, that ran fine on milspec SAE 10 - you needn’t worry about ZDDP. This isn’t a high-lift cam, or high-performance in any way, it was built for torque and reliability and it was built when oil still wasn’t very good.

You could run any oil in that and be just fine. I would pick a modern multi grade, like a 5W30, that is locally available, inexpensive, and change it often because of the moisture.

Synthetic is fine, if that’s what you choose, it won’t be worse for your plugs, and most modern oil formulations are synthetic blend anyway.

 

[kschachn]

Run a modern oil. Anything in a -30 grade or higher with an appropriate winter rating for your expected starting conditions. Ignore all the rest of the random fears you posted.

My old Sienna has gear driven camshafts, I use a Euro 0W-40.

 

[930.engineering]

I recently had the engine apart and it looks clean with no oil related issues other than hardening of the 50 year old seals on the pushrod tubes.

Jimmy, did you replace all seals?

.

 

[Jimmy C]

I replaced the front and rear main and all the seals on the pushrod tubes. I believe that is all the seals. I did not put valve seals in. New gaskets everywhere they had them. It is kind of weird in that it does not have gaskets everywhere. It has as a split crankcase like a VW bug that uses a sealant rather than a gasket. Cylinders to crankcase is also sealant. Cylinder to head is lapped with no gasket. I had low compression on on cylinder 4, I think due to leakage between cylinder and head. Also wanted to fix pushrod seals as they drip oil on jugs which holds dirt and messes up cooling.

 

[Hohn]

The biggest factor in choosing an oil will be seal compatibility. Many older tech elastomers relied an fairly aggressive swelling from mineral oils to have effective sealing.

If this is my engine, I'm using red jug Maxlife in 10w-30. Has mineral oil for swell, has seal conditions, has a reasonably good additive pack and is very cost-effective.

 

[RooflessVW]

IIRC that's a twice or thrice obsoleted milspec for HDEO.

A good 10W-30 or 15W-40 should be suitable.

 

[Jimmy C]

Hmmm…. I have no idea if the new seals are old or new polymers. Will mineral oil have a bad effect if the new seals are a modern polymer?

 

[kschachn]

Hmmm…. I have no idea if the new seals are old or new polymers. Will mineral oil have a bad effect if the new seals are a modern polymer?

No. All modern API licensed oils have seal swell limits and compatibility tests.

 

[Nessism1]

This would be a reasonable option.

 

[JavierH19]

It's just an old outdated diesel grade that existed for extreme cold when quality multi grades weren't a thing. Any modern gas/diesel oil like hdeo or euro oil will work. They tend to have 1000ppm of zinc and phos.

 

[wings&wheels]

I'll second the M1 Classic 10w-30 or a quality 5/15-40 especially if you are in a warmer climate, but the M1 will be more than fine.

As far as "modern" syns in classic vehicles, no problem at least nothing I've experienced, but then most of everything I like leaked from new....

Pic of the Pinzgauer please.

 

[SC Maintenance]

If you have replaced all the seals and there still new then I would use whatever synthetic you like.

If the seals are already saturated in conventional oil, then I would stick with that. I don't like the process of expanding the seals with conventional then adding esters after. I have nothing scientific to offer other than this theory has served me well over the years, but I have seen lots of old seals leak directly after pouring synthetic in, to which of course everyone replies "well it was old, would have happened anyway".

There are still several offerings of conventional without going boutique.

 

[JeffKeryk]

Unless an engine has elevated valve spring pressure, a nice 10w30 oil would work well. Add in modern detergent additives, etc...
If you wish, one of the classic oils out today will work.

Just think how many pre-1987 small block Chevy engines are still in service out there.

 

[burbguy82]

Cool truck.

Of course you should be running Liqui Moly, as it is made by Zee Germans.....nah they lost, go American:

https://www.mobil.com/en/lubricants...cants/products/mobil-delvac-1300-super-10w-30

 

[SR5]

Castrol Edge 5W30 A3/B4, had higher ZDDP at ~1000ppm (hence it’s API SL), it’s rated for both petrol/gas engines (A3) and diesel engines (B4). Plus it’s a 30 grade oil, which is what you require.

It’s a Group-III synthetic, so no esters or stuff to worry about seal compatibility. Basically Group-III “synthetic” is effectively a highly refined Group-II “mineral”. The same basic chemistry, just at a higher purity level.

 

[Faawrenchbndr]

I would use Valvoline VR1

 

[kschachn]

Which conventional oils use esters?

It’s a Group-III synthetic, so no esters or stuff to worry about seal compatibility. Basically Group-III “synthetic” is effectively a highly refined Group-II “mineral”. The same basic chemistry, just at a higher purity level.

In order to meet the Group III performance requirements it has to be hydrocracked, which involves the breaking of molecular bonds and recombination. It is synthesis, not just refining and purification.

 

[930.engineering]

It’s a Group-III synthetic, so no esters or stuff to worry about seal compatibility.

Anything API and/or ACEA isn't worth to worry about "seal compatibility".

Every step with refining or hydrocracking (group I to II, II to III/III+) or even true synthesis (group IV, with the exception of group V) inevitably leds to raising aniline point, say, to make it simple: less soluble. However, any serious oil company will compensate for this issue by adding the proper amount of either group I/II (cheap) or group V (AN or ester > $$$$) with any API or ACEA product.

Pure group III or even pure IV simply doesn't exist, in particular at Walmart.

.

 

[addyguy]

10W-30 HDEO would be perfect here.
Pics??