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Motorcycle Oil in '72 Mini? Crazy or Genius?

i changed my oil this summer in my 1972 Austin Mini 1000 and I got to thinking about the best oil (and ordering some “vintage approved” pricey stuff) and it occcured to me that since the transmission is in the sump and is lubricated with the motor oil, shouldn’t I choose an oil that would best stand up to those kinds of stresses? And since motorcycles share the same transmission lubrication method, wouldn’t motorcycle oil be the best option?

i only put a 800-1500 miles a year on the car during the summer and autumn. And I try and change the oil every spring (just because). So on the next go-around, does anyone recommend a switch to motorcycle oil? Does anyone have any experience with this type of change? Is the whole idea too clever by half?

Thanks
J

I don’t see a problem with motorcycle oil, but the stuff can be pricey and in motorcycles you are talking about less oil needed per oil change. Some synthetics for autos are too “slippery” and don’t work well in motorcycles and cause the clutches to slip. A synthetic motorcycle oil should be OK, but I wouldn’t use a full synthetic oil for auto’s in your car since it has a wet clutch.

Given your low miles I’d just use a good quality motor oil. I used Castrol GTX in several motorcycles with fine results. If it were me I’d just use the correct weight of Castrol GTX.

The peculiar circumstance of the motorcycles is their wet clutches. The Morris has a dry clutch and the gear box doesn’t cause any unusual problem with the oil.

I assumed if the transmission shared the same oil as the motor that a “wet” clutch similar to a motorcycle might come into play. If the clutch is “dry”, as all cars and trucks are to my knowledge, then sharing the same oil in the motor and transmission isn’t any big deal. My '03 Honda Civic can use 10W-30 in the manual transmission as a substitute until you can get Honda brand manual trans fluid. In most manual transmissions the oil is very similar to what is in the motor.

Some differences are the motor heats the oil, and the moving parts in the transmission can add to the “shearing” effect on the molecules in the oil. Still the OP is talking very low miles per year, so using any good motor oil of the proper weight will be fine.

If we were talking about racing and track days with lots of high rev’s and shifting then I’d say a motorcycle oil would offer more protection. Given the use described motorcycle oil would just add expense without significant benefit.

I’d think there would be classic Mini forums in England that would have all kinds of info on which oil to use.

Oil formulated for 4-stroke motorcycles still has the extreme pressure zinc additives that were greatly reduced in automotive oil to protect catalytic converters from the zinc…Flat tappet cams and lifters need this protection (steel against steel)…Most 15W-40 Universal or Fleet oil still has a full additive package and might be suitable for your Mini…While marketed for diesel engines, this oil is also approved for use in gasoline engines…

I’d use a diesel engine oil that will have plenty of ZDDP for your flat faced lifters. Motorcycle oil would be ok too but it’s been established that you don’t need whatever provision MC oil has for a wet clutch. A farm supply store here has diesel oil in straight 30, 10W-30 weights at reasonable prices and there may be more weights. You may not want the 15W-40 weight in cool or cold weather. There likely is undesirable but expected oil molecule shear due to high mechanical pressure along with movement at your cam lobe and non-roller valve lifter faces just as there is between transmission gears so diesel oil should be just fine.

Your 1972 should have no cat converter and so you should have no concern with converter poisoning from the ZDDP.

The clutch diagrams I can find for a Mini seem to be dry clutches, anyone know for sure?

Yes, I know for sure, that it is a dry clutch and I know that bmc a-series engines (as in this situation) NEED 20W-50 oil - as per the book and experience. You can use 15W-40 if you live north of Alaska during the winter, but otherwise you’ll loose oilpressure and those engines don’t take that lightly.

You should probably ask the question on a vintage Mini site. There is an entire subculture of vintage Mini owners and I’ll bet one of them will be able to make a good recommendation.

The Morris engine is the 3 main bearing 4 cylinder that was used in Austin Healeys, MGs, Wolseleys and Rileys, asterix. It’s been quite a while since I worked on one but never was aware of an oil pressure problem. In the 60s straight 30W was used with no problems winter or summer here in the south in most engines and I worked on several British Leyland cars back then. In A-Hs and MGs would peg the pressure gauge out when started cold even in the summer and after hours of hard driving they held 45psi at idle. I don’t recall any of the FWDs having a pressure gauge though. But my memory, like my good looks, has faded some in recent years.

Hi Rod Knox.
“The Morris engine is the 3 main bearing 4 cylinder that was used in Austin Healeys, MGs, Wolseleys and Rileys,” That’s correct.
And Kestrel’s. All the way from 803cc Minor, A30, 849cc Mini to 948cc Minor, Frogeye, Early Midgets, A35, 978cc Mini Cooper (rare today), 998cc Mini, Mini Cooper, 1098cc Minor, A40 Futura, Spridgets, Austin/Morris 1100 (or America) to 1275cc in Mini Cooper, Mini Clubman GT, Spridgets, Morris Marina, Austin/Morris 1300 + GT (or America). Also in the B-series engine (1522 cc, 1600 cc. and early 1800 cc. Around 1965 those got 5 mains).
I drive a minor today - well, has been doing that for the last 30-odd years - and that is the exact same engine as in the Mini - more or less, the specs are the same. If he has the original label on his valvecover, it states 20w/50 oil only. My experience is, that when you use 15w/40 instead, the oil pressure drops up to 20 % when hot in a good engine. Been there, done that. And I am talking high quality oil.
I admit to have a fading memory, but why is it that I am the only person to realise that I am looking better than ever?.
Have a nice day to all.

It’s likely they are all envious, asterix… But then, I never met “Ever.”

Many years ago I put a clutch in an Austin 1100 and it it was a learning experience. After replacing several clutches on domestic cars and trucks I though I knew everything. SURPRISE!

@RodKnox is correct. I would suggest though that you take a look at this: http://www.britishminiclub.co.uk/ It is the Mini portion of an online car club that I’m a member of in the MG portion. Someone there will have the answer that you need. My thinking is that motorcycle oil is not needed or desireable, but that’s just me.

Everyone, thanks for the replies. I had lurked in mini forums, but most oil discussions involve recreations of old formulas. Pricey stuff, to be sure. I have to digest everything everyonehas written here before I make a decision, but I’ll keep this post updated. Being in rural michigan, unless I purchase online, I’m stuck with what the local shops offer.

Keep 'em running!

The issue with modern oils in Mini’s, or any other older British or even American cars for that matter is unfounded I believe. This became very controversial a few years back when someone had their Triumph motorcycle engine rebuilt and within a month, the cam lobes were worn completely off.

His mechanic told him that the reason was due to the SM oils having less of that ZDDP and Molybdenum Disulfide. He got on the internet to warn everybody and it started the myth about the oils.

It turned out that part of the rebuild involved regrinding the cam. What I believe happened was that the cam grinder was probably a young guy who was not aware that before sometime before the 70’s, all cams were made from a mild steel that had to be case hardened after machining. The case hardening is very thin and if it gets ground off, the underlying steel will not last long unless the cam is re-hardened.

Sometime in the 70’s, harder and more durable inserts came out for machining so cams and other components could be made from harder alloys. It saved enough in labor by cutting out the hardening step to more than cover the additional cost of the higher grade steels.