Oil suggestion for a classic mini?

[Brit33]

Originally Posted By: 2Slow
Even if the engine would prefer lower viscocity, I am a little leary about lowering the viscoscity much as it is the same lube for the trans sump. Many manual trans / axle configurations run a fairly high viscocity lube compared to 40w engine oil.

The seals are the same between my engine and the Cooper S, so I doubt there would be any issue going to the 70 PSI spring, but I doubt I should mess with a system that works.

-Joe


yep it's kind of a strange combo. Never understood using the same oil for your trans.
My alfa trans requires a 80w90!
Can't imagine how it would feel with a 40wt oil.

Those trans are also very HP points.
I have Motul HP Moly treated oil in my gear trans.
Maybe a Liqui Moly oil that's got plenty of anti-wear moly in it for the trans? You could possibly use a lighter oil then.

What's the factory recommendation?
Do you know that the factory OP recommendations are?

My alfa manual states what the min and max OP should be.

 

[CATERHAM]

Originally Posted By: Brit33
Originally Posted By: 2Slow

-Joe

My alfa trans requires a 80w90!
Can't imagine how it would feel with a 40wt oil.

A 90wt gear oil has roughly the same viscosity as a 40wt motor oil so the T6 5W-40 is certainly not too light.

As I suspected the T6 is still heavier than necessary since you can't use maximum rev's without going into by-pass mode even when the engine is hot. Mobil 1 0W-40 would have been a better choice.
Anyway you're running the T6 now and I'd stick with it for the time being.
The fact that the engine is leaking more than the very heavy 20W-50 is no justification for running grossly OTT heavy oil from a proper lubrication perspective.
Short of replacing the leaking oil seals I would try adding a seal swell additive, Gunk makes one that will not increase the oil's viscosity or just live with the leaks.

 

[2Slow]

Manual basically says to use 20w-50. Scan of the manual below:

 

[CATERHAM]

And that recommendation is what, 40 to 50 years old?
The 20W-50 grade of the 60's and 70's was a very shear prone oil, as were all multi-grade oils of the day although it did have a cold start advantage over a straight 30wt oil.
After 1500 miles you'd be lucky if you still had a heavy 30wt.
As you have learned first hand, a modern shear stable 20W-50 race oil is way too viscous for your application, in fact so is the synthetic T6 5W-40.

 

[mechtech2]

Originally Posted By: Brit33
Originally Posted By: 2Slow
I can purchase a Cooper S spring for $4, that would bump the bypass pressure to 70 PSI, is that something you guys would advise?


noo. the bypass pressure was designed for your engine in mind.
If you exceed this pressure, seals can pop, filters explode, gaskets leak etc.

I would never alter the bypass spring rate.



Just find a thinner oil to suit the engine.



No seals or gaskets are under pressure in engines -[ maybe blowby pressure of 1/2 lb].
A 40+ year old spring lost some of it's oomph, BTW - no problem with replacing it.

 

[Falcon_LS]

Originally Posted By: Brit33
...drop the oil to a 30wt and see what happens.


If you're going down that route, preferably opt for one that meets ACEA A3/B4 spec, and not ILSAC GF-5. Perhaps something like Pennzoil LongLife Gold 10w30?