7 replies to this topic

[71bay]

Handbook says 10w30 is that the best or 20w50 

or makes no difference ?

Thanks

[cooperhawk]

10-50 correct

[Steve220]

20w50 mineral. Change every 4-5k miles.

[absx2]

As above 20w50 classic oil if you want to keep your gearbox in good order.

My favorite is Valvoline VR1 but if your not revving the guts out of it all the time Minispares do a good own brand oil as do Halfords.

There are also good 20w50 oils from Millers, penrite, Castrol, Silkolene and a few others, just steer clear of cheap supermarket branded oil and change it regularly.

I usually change the oil at around 3000 miles, its cheaper in the long run. 

[71bay]

Cheers guys

[bluedragon]

There is no technical or scientific reasoning behind 20-50 oil being inherently superior for a Mini, gearbox or otherwise, in the modern era. Think about what the ratings mean.

 

"20" means it acts like a 20 weight oil when cold. "50" means it acts like a 50 weight oil when hot. This was important back in the days when oils had limited viscosity ranges. In harsher conditions, a 50 weight oil was needed to maintain an adequate oil protective film when hot.

 

But modern oils (especially synthetic) are far superior to those vintage oils in their ability to maintain their lubricating film and consistency when hot. An excessively viscous oil just increases parasitic engine power losses and makes it hard to start when cold. Also, heavier oils take longer to reach operating temperature (which I have personally observed) and often cars running the 20-50 never reach proper operating range (particularly when used for shorter trips.)

 

And when cold, who cares if it's 20 vs. 10? 20 just makes it harder to start. The reason for starting at "20" for a 20-50 is that conventional oil (non-synthetic) requires additives called viscosity improvers (VI) to obtain multi-viscosity properties. VI gets depleted and breaks down with use.

 

But if you push the viscosity spread too far, then the VI is beyond its limits and breaks down faster. Which leaves you ultimately with a straight 20 oil. The narrower the range, the better, for a non-synthetic oil. So starting at "20" and ending at "50" keeps the spread manageable. But 10-30 is narrower.

 

Synthetic oils have inherent multi-viscosity properties built into their molecular structure and need little to no VI additive. This means they resist breakdown and loss of multi-viscosity properties far better than conventional oil.

 

The only scenarios where I would use the more viscous oil would be 1) I had a worn engine that was consuming (not leaking) oil or 2) I was running the car hard for extended periods of time in very hot climates (38+°C.)

 

If I were running a synthetic, I wouldn't even worry so much about the hot climates. Synthetics are far more stable and resist shearing much better (perfect for a gearbox), tend to have less friction, and don't break down nearly as easily when subjected to harsh conditions. There's no reason why these are unsuited for a Mini, and many reasons why they're better. Just ask Keith Calver.

 

I personally believe the reactionary oil myths really had their birth because of dodgy Rover quality control in the 90's. About when the handbooks switched to 10-30 recommendations (since Rover realized oil technology had progressed) quality control sank. (recall the notorious 2nd gear synchro and MPI cam issues.)

 

At the time, the 10-30 recommendation was indicted as the cause, but we now know indifferent manufacturing was the real cause of most of these problems. (in a similar vein, the rash of slider cam failures in the mid 2000's then generally was attributed to lack of zinc diphosphate [ZDDP], but in fact turned out to be poor quality control in most cases from outsourced cam manufacturing.)

 

[Alpenflitzer]

If you go on calvers page he explains the additives which are important to a mini where the oil is for engine and gearbox at the same time. I prefer Millers Mini Oil which has the necessary additives 20W50 all year round. If not available or in urgent matters I am using Harley Oil 20 W 50.

[jamesmpi]

http://www.theminifo...c/#entry3401296

Posted this before. Millers 20w50 CTV is what I use

Edited by jamesmpi, 15 August 2016 - 07:12 PM.