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#1 croc7

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Posted 26 January 2022 - 07:21 AM

While browsing through a Haynes manual (#646 with light blue cover) Chapter 14 supplement, I read where the oil recommendation has been changed from 20w/50 to 10w/40. Curious to know the benefit of the change.

#2 Arthy

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Posted 26 January 2022 - 12:10 PM

While browsing through a Haynes manual (#646 with light blue cover) Chapter 14 supplement, I read where the oil recommendation has been changed from 20w/50 to 10w/40. Curious to know the benefit of the change.

 

I've found it's best to stick to a good quality 20w/50, due to the gearbox sharing the same oil.



#3 nicklouse

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Posted 26 January 2022 - 12:11 PM

It was to do with the CAT.



#4 Tones61

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Posted 26 January 2022 - 03:35 PM

10/40 is the spec for autos and for mpi's,
As nick said,also to do with emissions and catalyst :-)

Edited by Tones61, 26 January 2022 - 03:36 PM.


#5 whistler

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Posted 26 January 2022 - 05:50 PM

10w/40 was also the recommendation for cold climates. I used to sell Castrolite 10w/40 to winter customers back in 60's/70's.



#6 Midas Mk1

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Posted 26 January 2022 - 06:30 PM

Nothing to do with emissions, it was rover standardising oil across the range.

No one clued up uses 10/40 in a manual a series.

#7 croc7

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Posted 27 January 2022 - 02:06 AM

Nothing to do with emissions, it was rover standardising oil across the range.


No one clued up uses 10/40 in a manual a series.


OK then. Good to know that I’m clued up as I’ve been using 20/50 for years. Was Castro GTX but like Valvoline VR-1 better.

#8 timmy850

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Posted 27 January 2022 - 04:42 AM

The original Mk1 manual says SAE30 above 0C ambient temp

The later Mk1 manual says 10W/30 or 10W/40 above -18C (with a note that 20W/50 or 20W/40 may be used above -12C ambient)

You need the oil to be thin enough when cold to enable near-instant oil feed to the rockers & camshaft and thick enough hot to give good oil pressure. Plus in a mini keep care of the gearbox

#9 croc7

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Posted 27 January 2022 - 07:12 AM

Thanks all for the replies. My ownership of minis has been limited to the older carb cars. So, with my scope of experience with the mini, I forget to consider that there are minis out there with automatic gearboxes, CATs, fuel injection and sensors that would have different lubricant requirements.

Edited by croc7, 27 January 2022 - 07:15 AM.


#10 MatthewsDad

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Posted 27 January 2022 - 08:06 AM

I think many myself included use 20w50 on their cat / injection cars. The manual gearboxes are no different from the earlier models, that's what I base my choice of oil on.

#11 cal844

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Posted 27 January 2022 - 02:39 PM

Use a 20/50 oil across the rage, even on CAT equipped engines.... Rover went to a 10w40 oil and had alot of warranty claims for gearboxes and indeed complete units in the mid 90s(Iirc)

Edited by cal844, 27 January 2022 - 02:40 PM.


#12 Miki Leyland

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Posted 27 January 2022 - 11:01 PM

What could be the problem using 20W50 with a catalyser?



#13 bluedragon

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Posted 28 January 2022 - 01:06 AM

There is no issue with 20w50 and catalytic converters. Any oil related concerns with catalytic converters deal with the oil specification ratings - specifically, the amount of zinc or zinc-based compounds in the oil.

 

More modern (mid 2000's on) oil ratings specify lower levels of zinc to avoid poisoning the catalytic material. Any 20w50 oil with a modern rating will be perfectly safe with a catalytic converter.

 

As to the necessity of 20w50 for Minis, I disagree with most other opinions. The oil viscosity index has little relation to the lubricating properties or the shear strength of the oil molecules. It primarily deals with how the oil flows when cold and its properties when hot. The "50" means it acts like a 50 "viscosity" oil when hot. 

 

With older vintage oils, where the oil molecules are less stable and prone to shearing and decomposition, this could be important in hot conditions. With modern oils, especially synthetics, the molecular chains are much stronger (synthetic molecules are engineered stronger and don't need as many perishable additives to gain multi-viscosity properties.)

 

For a non-synthetic oil, I would guess that any real problems with 10w40 was related to the wider viscosity spread. Natural oil is single viscosity by nature.

 

As I wrote, additives are needed to give conventional oil multi-viscosity properties. The wide the spread, the more additive ("VI improver") needed, and this breaks down faster under duress. Perhaps the 10w40 broke down more rapidly than owners expected, I don't know.

 

But I'd want to see proof of that, like records of Rover's warranty claims, vs. anecdotal testimony. If these problems were that bad there should be evidence from warranty returns, since the then-new injection Minis would have come with 10w-40 as factory fill and likely be dealer-serviced for at least the warranty period if not longer using the same oil. Enough failures ought to have resulted in a class-action lawsuit against Rover.

 

 

Dave



#14 Steam

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Posted 28 January 2022 - 03:32 AM

Penrite classic oils are very good. Classic Light or Classic Mini.
https://penriteoil.c.../brands/classic
Enjoy. :-)

#15 KTS

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Posted 28 January 2022 - 01:06 PM

viscosity aside, the other factor that needs to be taken into account with 

 

There is no issue with 20w50 and catalytic converters. Any oil related concerns with catalytic converters deal with the oil specification ratings - specifically, the amount of zinc or zinc-based compounds in the oil.

 

More modern (mid 2000's on) oil ratings specify lower levels of zinc to avoid poisoning the catalytic material. Any 20w50 oil with a modern rating will be perfectly safe with a catalytic converter.

 

 

on this point, it's my understanding that the manual gearbox needs an oil with decent amounts of zinc etc compounds to avoid excessive wear on the synchro assemblies, so this as well as viscosity should be taken into account when choosing an oil






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