88 replies to this topic

[ImagoX]

20w50 is ideal in any mini engine, as the gearbox runs in the sump.
look at any modern car, and you'll see that they use a thicker oil (like ep80w90) in the gearbox, and a 5w30 in the engine.
now you can't fill a mini engine with ep80w90 gear oil, its just too thick for the oil pump to cope, but will make your gearbox last ages. so the next best thing is 20w50, its thick enough for the gearbox to feel slick without premature wear, and thin enough to pass round the engine's oil galleries and bearings. I run valvoline racing 20w50 (roughly £19.00 for 5 litre) in my mpi, and millers CTV 20w50 in the 1380. the ctv is about £35 for 5 litres, but is specifically designed for gearbox in sump applications like the mini, something to do with the chemical compund, makes it suitable for gearboxes and engines.

the mpi used to run on 10w40, which i think is too thin for any mini, purely because it gives the gearbox very little protection. the gearchange used to be quite notchy and stiff, i put the valvoline 20w50 in, the engine is much smoother running, the gearbox is quieter, the gearchange is super slick now its like a new gearbox. and the annoying leak that nobody could cure has gone!

20w50 is the future!

With every post, I feel better and better about my oil leak - hopefully I'll clear it up shortly - thanks!

The Valvoline "racing" oil you use - is that the VR1 formula in 20W-50 grade?

http://www.valvoline....asp?product=50

[Grayedout]

ep80w90 gear oil, its just too thick for the oil pump to cope

Whoa stop stop stop !!!!!!

The numbers 80 & 90 on a gearbox specification DO NOT relate directly to the 30, 40 & 50 on an engine oil grade !! They are just categories and the actual viscosity values can be quite similar.

Therefore do not always assume a higher number means a higher viscosity !

I'll post the actual values when I get back to work tomorrow !

[Grayedout]

The Valvoline "racing" oil you use - is that the VR1 formula in 20W-50 grade?

Looks good to me !!

[mini93]

The old 'oil' debate......

For the record I run mine on 5-40 fullly synthetic superbike oil.

Make of that what you will.

will this be recomendations by KAD for use with the head and running syncroless dog box??

[taffy1967]

20w50 is ideal in any mini engine, as the gearbox runs in the sump.
look at any modern car, and you'll see that they use a thicker oil (like ep80w90) in the gearbox, and a 5w30 in the engine.
now you can't fill a mini engine with ep80w90 gear oil, its just too thick for the oil pump to cope, but will make your gearbox last ages. so the next best thing is 20w50, its thick enough for the gearbox to feel slick without premature wear, and thin enough to pass round the engine's oil galleries and bearings. I run valvoline racing 20w50 (roughly £19.00 for 5 litre) in my mpi, and millers CTV 20w50 in the 1380. the ctv is about £35 for 5 litres, but is specifically designed for gearbox in sump applications like the mini, something to do with the chemical compund, makes it suitable for gearboxes and engines.

the mpi used to run on 10w40, which i think is too thin for any mini, purely because it gives the gearbox very little protection. the gearchange used to be quite notchy and stiff, i put the valvoline 20w50 in, the engine is much smoother running, the gearbox is quieter, the gearchange is super slick now its like a new gearbox. and the annoying leak that nobody could cure has gone!

20w50 is the future!

Well put mate!

[danwebster]

The old 'oil' debate......

For the record I run mine on 5-40 fullly synthetic superbike oil.

Make of that what you will.

will this be recomendations by KAD for use with the head and running syncroless dog box??

Not at all no, this was my own idea after months of research prior to building the engine. I ran it with the synchro box too.

Gearboxes lasted much longer than my brothers used to (he's been running a KAD engine since 1993) and he used to use valvoline racing oil that so many swear by.

The reason many people get such good results from Valvoline racing is the high zinc content of this oil, one of the highest of all the car oils. Zinc is the element within the oil that protects where metal to metal contact takes place. If your oil is working correctly the only place this actually happens is the gearbox.

Motorbike oils are designed for engines that share the gear oil with the engine, just like a mini. Its worth noting though that they are also designed to accomodate engines that run a wet clutch, therefore they don't have all of the friction reducing additives that some synthetic oils have, on a low mileage engine like mine though this isn't a problem.

[Grayedout]

As promised some numbers !!

Engine oil viscosities range at 100°C

20 == 5.6 - 9.3 centistokes
30 == 9.3 - 12.5
40 == 12.5 - 16.3
50 == 16.3 - 21.9
60 == 21.9 - 26.1


Transmission oil viscosities at 100°C

70W == 4.1 centistokes minimum
75W == 4.4 min
80W == 7.0 min
85W == 11.0 min
90W == 13.5 - 24.0
140W == 24.0 - 41.0

So you can see that a 90W transmission oil can actually be THINNER than a 50 wieght engine oil !!!!!

Hope this helps !

[Jupitus]

I think you made up the word 'centistokes', but I like it

[ImagoX]

The reason many people get such good results from Valvoline racing is the high zinc content of this oil, one of the highest of all the car oils. Zinc is the element within the oil that protects where metal to metal contact takes place. If your oil is working correctly the only place this actually happens is the gearbox.

Motorbike oils are designed for engines that share the gear oil with the engine, just like a mini. Its worth noting though that they are also designed to accomodate engines that run a wet clutch, therefore they don't have all of the friction reducing additives that some synthetic oils have, on a low mileage engine like mine though this isn't a problem.

Isn't there a zinc additive that one can add to motor oil to boost this? I know that modern oils are taking out elements like this (mainly because they shorten the life of the cat or so I hear) - would putting them back in via an additive at every oil change be beneficial?

[Grayedout]

Always a risky business adding extra additives as believe me we spend millions of dollars and many hours of engine testing getting the balance just right. Adding one thing is nearly alwasy to the detriment of something else and if you suddenly throw in an excess of one additve then it may well do its job but something else in the engine may well suffer !

[Ethel]

Google says a centistoke is a unit of kinematic viscosity 'n viscosity is measured in poises

[Grayedout]

All those values are Kinematic Viscosity !!

[Se7enS1ns]

One for the FAQ's methinks Mods - very informative, i like it!

[adammini]

I have only used Unipart silver 20w40 (semi-synthetic) since I built my 1380 engine and box 4 years ago, which has done about 25k.

A bearing in the box is on its way out now. Thing is it ran beautifully untill recently, im now thinking that it the oil may have been a bit too thin so the thicker 20w50 may be the best way forward.
I changed the oil every 3k religiously so is a bit irritating the box has gone, but hey it wasnt desgned to have 100 horses going through it!

[Jake Blues]

Just to add another anecdote, I had synthetic oil in my 95 1600 Astra but it started to smoke and rattle when cold. I switched to non-synthetic at the next oil change (on advice) and have had no trouble since!