Let me suggest a simple test for all 20wt multi vis oils. with your mini loaded up with the maximun weight it can handle, find a place with no traffic. from a complete stop, floor it in first, then speed shift into second and and keep the pedal to the floor until you hav reached top speed for 2nd. now for the fun part, push in the clutch with the gas pedal still at wot and FORCE SHIFT into 1st, then side step the clutch. repeat 5x YOU CAN DO IT  if you have the strength. If you do not have the strength or the balls then find a pro driver to do it. Or you could just use st 50wt. Back in the late '70s a guy named gary from burbank taught me this test that he used before he would buy a car, Merry Christmas

Been using Red Line 20W50  Motorcycle syn. oil in my mini since day one, seven years ago, no leaks engine runs great. little to no debris on my magnetic drain plug.  Has the correct amount of zinc.  I buy it by the case from Amazon with free shipping. 

Yeah Benny, like Amsoil.  It may be very good, but such a pain in the keester to buy you wonder what's up.

Not only is their website sort of 'clunky', but they make their oil fairly difficult to buy (in my neck of the woods) by only selling it through a select group of distributors.  I spoke to their distribution manager about this last year, and he basically told me "Yeah, we know it's a pain, and we are actively seeking out more distributors, and working on setting up a better network".

Nevertheless, it's a great product, and worth the extra effort in my opinion.

+1 for mur here.  The Brad Penn is an interesting new discovery thanks to this thread.  However I wouldn't be interested just based on that website of theirs.

Thank you all for the replies. I think I will give Brad Penn a try. Thats what the majority of you guys recommended. Thanks.

Happy Holidays

All great in theory, but would only be of any legitimate concern if you were putting peak loads on your gear teeth with cold oil....given how quickly a Mini warms up its oil, only a fool would go to the trouble of building themselves a 1380, and then do such a thing.  Straight 50 wt. also has the downside of being hard for the engine pump to draw when cold, so while you may be attempting to help your gearbox, you are likely doing so to the detriment of your engine.

Now, let's expand you oil "knowege" to the MGB gearbox that uses straight 30 wt.  By your own reasoning, shouldn't the load capacity of the oil in that gearbox already be too low from cold, and then only get worse as the oil warms up?  Strange then that later MGB gearboxes are considered virtually failure-proof......  

I think I will try the Brad Penn oil as a result of this thread.

I have been running Mobil 1 20W50 in my road trip minis for decades.  The hot oil pressure is always awesome, and the gearbox wear has been nearly nonexistant.  I have an early MK III box that looks new with well over 100 000 miles on it.  This particular box did only 16000 miles in the seventies and then the car sat till 1998.  It has had Mobil 1 since it was brought out and became my daily driver.  The oil never stays in for more than 2000 miles, often 1500 is the change point.  

Another car in the fleet has a heavily miled out 1380.  It is hardly used, but when used it is used hard.  It used to eat an idler gear up in about 15000 miles, but I guess it sees less gratuitous wheelspin anymore as the drop gears in there now are quiet and have been for over a decade.

A car that I look after sees limited mileage and light use by its present owner.  That car will be fine with 2 oil changes per year and an inexpensive 20W 50 oil.

here is some knowage for you to attack. 20wt multi vis oils have long molecules that increase viscosity when heated, the lighter viscosity makes it much easer to start in cold weather and uses less power than st 50wt. That is very good for engine oil on any car that does not use the same oil for trans/diff.  As the mini uses the same oil for all 3 tasks, the gearbox shears these long molecules and the viscosity drops off almost instantly. Shear strength and load capitacy are to low to start with for trans/diff requirements in the mini, so out of the bottle you are out of spec, and it just goes down hill from there. In a catastropic failure due to poor lubrication, would you be able to claim against any 20wt multi vis oil? Answer is NO. I recommend castrol or kendal st 50wt, Have a nice day

I'll break this up, so it's simple enough for you to follow along:

• "HOW IN ANY WAY DID YOU PROE ME WRONG?" - You claimed most 60's gearboxes required 90 wt. oil, so I gave you specific examples of BMC gearboxes that don't.  
• "where are your facts and what oil do you recomend." - The factory manual, and I use Brad Penn 20w-50
• "you are afraid to make a choice" - Hmmm, I've stated clearly what I use.....no fear
• "and you attack someone who has infinatly superoir knowege" - You obviously have a great deal of knowege
• "show me anything you have to cintribute to this discussion" - I'm waiting for you to show us your contribution first...where's your data?

HOW IN ANY WAY DID YOU PROE ME WRONG? where are your facts and what oil do you recomend. you are afraid to make a choice and you attack someone who has infinatly superoir knowege. show me anything you have to cintribute to this discussion

No, but you were the one who claimed gearboxes of the period need heavier oil, so I proved you wrong.  If an engine doesn't require heavy oil, and a gearbox doesn't require it, why would the combination of the two require it?  What was it you said...."not my opinion, just a few facts"?

I'll go with the factory on this one, and decades of real world data, rather than some loud-mouth on the internet. 

Ok so now we compare mini engine oil with spridgets and ups trucks. do either of the latter use the transmission sump for ampick up point, JUST USE THE FVCKEH 50 WT. PERIOD

1990 Owner's Manual (AKM 6579), Page 32

//i98.photobucket.com/albums/l280/gary21sn/OwnersManualPage321_zps3f79456d.jpg

No, we understand your point....it's just flawed logic.  Saying that most transmissions of the period ran 90 wt, so 50 wt makes a nice compromise is just flat wrong....most BMC products in the 60's ran their gearboxes on 30 wt engine oil (MGBs, Spridgets, etc).  I have a factory Mini workshop manual in front of me, and for climates above 10 degrees F, they recommend anything from 10w-40, to 10w-50, to 20w/50 depending on the brand.  In extremely cold climates, they recommeded oil as 'light' as 5w/20.  Continue on with impunity if you like, but in the age of information, ignorance is a choice.

I agree with Kermit's comments to a degree....oil is like tires....what was "race quality" in the 60's wouldn't even be considered street car quality today.  However, the reduction in ZDDP levels a few years ago changed that conversation when it comes to oil.  I realize this subject is like climate change, where some people believe it and some don't, but I've seen enough damaged cams and lifters in recent years to make me stick with the ZDDP levels that these cars were designed for.  That's why I run Brad Penn, or at the very least, add a ZDDP additive from someone like Redline Oils. 

20W oil is "thicker" at the temp it is rated at (for 20/50 oil) compared to 50W at the temp it is rated at (for 20/50 oil) so why the concern for the 20W being too "thin" ?

If it really is warm all the time where you are, then you can run straight 50w . All this concern about multiviscosity, in my opinion, is mainly for increased fuel economy, unless you live in the frozen north where subzero oil is a problem . Back in the 1960s -1980s I had non-mini cars with well- over 100,000 miles using straight 30W or straight 40W.

Someone will interject that most wear is at startup and thinner oil flows better to protect from that. Same answer as above. Also, a friend is a UPS mechanic. Their drivers shut off their engines at every stop to save that minute or two worth of fuel  - multiply that by umpteen stops per day and that is a lot of potential "startup" wear and tear, yet their engines routinely go 400,000 miles. Granted, those are warm restarts.

I guess you can't understand my point about strait 50 wt. First, before you start the engine, what you have in the sump is transmission/ diff oil. Straight 50 wt castrol makes a good trans /diff oil, then as you engage the starter you suck the t/d oil out of the sump, through the oil pump and then the filter to the engine. This oil needs the properties of both engine oil and tranny/diff oil and the lower test temperatures for tranny oils are irrevalent because the oil is exposed to engine temps and not just tranny temps. I will go with my st 50 wt with impunity

The viscosity index for gear oils is not the same scale and test temps as used for motor oils.
You can't just compare the two based on those numbers.
Also, the 20W rating is when the engine is cold, at normal running temps a 20W/50 behaves like a 50 grade.

{edit} viscosity chart added //www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm 

Thanks Kermit, great info in a usually difficult thread topic. 

Race car, Brad Penn.   Street cars,  whatever.  Oils today are sooooo much better than 20 or 30 years ago.  Racing a mini in the old days many times needed two oil coolers and a hot streeter need one.  Today one on the racing mini and an oilstat is recommended.  A streeter wouldn't need one unless it was really radical.  Nope, in my opinion finding a good oil just ain't that big of deal anymore.  Most of what is on the shelf today is good enough for typical driving.