OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk What Oil and Fuel to Use in 1960s Engines?

I have an old Southern Cross KXD-2 4-stroke mower. My dad used whatever fuel and oil that was available, although he never touched the ethanol-blended stuff. I'm pretty sure he used whatever was regarded as "standard" fuel through the ages, and converted to S.A.E. 30 in more modern times.

However as that old ad use to go: "Oils ain't oils!"

My 1960s manual recommends S.A.E. 40. However I am sure the S.A.E. 40 labelled oils today are not the same thing.

Can anybody recommend the best fuels and oils to use in a 1960s mower?

Also, are any of the "additives" being marketed by some companies any good, or are they just expensive "snake oil" treatments?

Well you are on the right track avoiding that disgraceful E10 product. Many a Victa prism fuel cap has succumbed to that garbage in my experience, necessitating a time consuming tank clean out and fuel tap replacement.
I'm sure a good old 1960s motor isn't made up of exotic Ferrari grade metals and standard 91 octane unleaded will work fine (where you can find a pump!).
As for oils, I'm sure a current 40 weight oil as you mentioned hasn't changed sufficiently to do any harm. Others here will have more knowledge on this.

G'day vint_mow,
As far as fuels go, I much prefer no-ethanol 95 Premium. It has a much longer storage life than 91, and much less gumming tendency.

An SAE40 oil of today is very different from those of the 1960's, in terms of additives like detergents and anti-wear compounds. But a monograde SAE40 oil still meets the same viscosity standards as it did then!

You can get away with say a straight mineral 20W-50 multigrade, but it may burn a little bit, if the engine sees regular use. Synthetic and semi-synth blends are a complete waste of money here.

Penrite market some multigrade oils for classic car and motorcycle engines which are entirely suitable, e.g. their 'HPR40' which is 25W-70 viscosity, and readily obtainable.

Additives - <sigh>. Some of them can have advantages in specific applications, like gear drives in particular. Engines - not so much, as a rule. Their actual effects need to be monitored by an oil analysis program - which is worthwhile in heavy industry, when you're talking hundreds or thousands of litres for an oil change.

But the majority of them, are as you say, in the 'snake oil' class.

Thank you. I appreciate the very helpful replies.

Well just like oils, the plot has thickened!

Prolube Monotec 40 has just been recommended to me as a good oil to use. Prolube make it in 5 litre and 20 litre containers. Does anyone have any experience with it?

Interestingly, Penrite's technical department recommended I use S.A.E. 30 4-stroke Mineral oil. They also mentioned that they make an S.A.E. 40 Monograde that is mainly sold for use in older diesel trucks, but which would be entirely suitable for 4-stroke petrol engines. Problem is it only comes in 20 L drums!

This is what the original manual says about oil specifications.


This article provides a good "translation" of the old API service standards to the more modern standards:

OIL CONSIDERATION TO LENGTHEN ENGI...ion Agricultural, Utah State University.

More just to hand from Penrite's oil Techs.

Penrite SEFS 30 is not an oil for modern cars, of course, coming in at API SG.

API petrol ratings are now of the form S*, with SN being the latest/highest �SG came out in 1989.

The �MS� rating to which the manufacturer referred is now API SD, so the (higher) SG is suitable.

Penrite has an oil at SAE 25W-70, which covers for an SAE 40 and is rated at API SG. This is Penrite "Classic Medium".

The code for 5L is CLASM005.

G'day vint_mow,

I should mention here, that I have a significant technical background in lubricants; including wear metal analysis of used lube oils, for machine/engine condition monitoring programs.

Personally, I wouldn't go out of my way to insist on a monograde SAE40 here. Any decent modern oil is going to be way ahead of what was on the market back in the 1960's. I.e. as regards its tribological properties, detergency/dispersancy, anti-wear characteristics, oxidation resistance - the list goes on!

What we have here, is a small capacity, low specific power output [i.e. in kW/litre terms], air cooled, spark ignition, single cylinder side valve engine, with splash lubrication.

Penrite therefore make a very good point, when they recommend their SAE30 monograde small engine oil. A type which has worked very well in the very similar B&S and other US-made analogue engines, for many years now.

Yes, diesel service SAE40 monogrades were around from the late 1930's, and were formulated as OEM specified oils for GM/Detroit 71 series supercharged 2-stroke diesel engines. From the 1-71 single all the way to the 24V-71 V-24! 71 cubic inches/1162cc was/is the cylinder capacity.

As these 'Jimmies' always had fairly high oil consumption, any improved lube oil formulations have had to use low-ash additives, to minimise combustion chamber deposit formation. Lube oils for spark ignition air cooled piston aero engines have the same limitation incidentally, as oil consumption there is high too, by modern standards. Particularly for the radial types.

The thing is, there are more effective additives, that can be used where the 'low ash' constraint doesn't apply. Particularly on the anti-wear side. So a diesel rated SAE40 monograde is not necessarily superior to an SAE30 formulated for small engines, and may in fact result in shorter engine life, in this application.

Thanks Gadge,

I greatly appreciate your technical expertise and advice on this interesting subject.

Do you think the S.A.E. 30 may in fact be the best "compromise"?

Incidentally, my dad had always used S.A.E. 30 in the old Southern Cross. I think it did always smoke a bit, but no more than usual for these kinds of engines.

Definitely yes, as a convenient, workable solution.

After a wee bit of thought [meh, it's an incurable habit with me], it has occurred to me that the SAE40 Diesel spec oil is probably what Southern Cross specified for use in their small diesel engines at that time, which was one of their major product lines.

And as their target mower customers were very much their existing customer base, they would have seen no reason at all to want their customers to source/stock a mower-specific engine oil, when one that these customers already had on hand, would work just fine.

Thanks Gadge,

Yes I noted before the coincidences with Southern Cross selling diesel engines, then branching out into mowers, and recommending the same oil for both. I also suspect that the Bendix air filters they used on their diesel engines were also the same or similar filters that they used on their mowers.

I will give the Penrite S.A.E. 30 4-stroke oil a try.

When I was working on the spanners our workshop used Ampol Longhaul diesel oil in everything that came through the doors, from the smallest Briggs right up to a D5. All vehicles still had full manufacturer warranty. It was 15/40 grade, oil changes every 10,000km.

Yep, I seem to recall that Ampol was one of the first oil companies to market a 'universal' engine oil to the agriculture market segment, back around the 1970's. Convenient for cockies, as they then only had to keep one drum of oil on hand, rather than three or four.

Sadly, this is another oil that has gone the way of the Dodo.

Along with the Ampol brand itself. I still have a couple of part 2.5kg tins of Ampol greases, as their depot was the most convenient back then, when I needed big tins of grease, or bulk kero.

Most of my grease use these days is in cartridges for my grease guns, as even when packing bearings I use a grease gun and bearing packer now.