Best oil for the A-Series

[Boyscout]

Like most Mini enthusiasts, I want to be sure that my Mini engine gets the best lifeblood. I am quite passionate about oils and have done extensive research on the best oil for the A-Series. The Mini engine is quite a unique animal in that it shares its engine oil with the gearbox. This coupled with the fact that it still employs a "flat tappet" valve train makes it require an oil which has high levels of ZDDP. (Zinc dithiophosphate)

Now older oils had ZDDP in abundance and it was never a problem. Now modern cars with catalytic converters do not like high levels of ZDDP as it blocks the cat. Most modern oils have had the ZDDP content greatly reduced to comply with CAT specifications.

If you use oil specifically made for Classic cars it usually does have a high enough ZDDP content as well as some of the racing oils, Indy oil is one. I also found that the classic oils have a viscosity of 20W50 which is really thick when cold. This is not ideal as you would like to get it circulated as soon as possible and an oil with a lower cold (W) rating would be more suitable.

I have tried a number of oils and to date I can not find anything better (IMHO) than Caltex DELO 400. This oils is made for Diesel but is also applicable to mixed fleet. It has adequate levels of ZDDP so the gearbox and the tappets (not the ones driving the car  ) will be happy. It also has a viscosity of 15W40 so it circulates better. Even though it is classified as a mineral oil the specs exceed many full synthetic oils.

I have been using Delo 400 for a while now and have found that the oil pressure is more consistent from cold to hot and the engine is generally smoother. The gear shift is also slightly better. Previously I had a scratchy shift into 2nd gear with Castrol GTX and GTX High mileage. After a while when the oil was up to temp it was better. With the Delo it is fine from cold.

It is also not very expensive, you can buy it from Midas and Makro for less than R300 per 5l bottle

 https://www.makro.co.za/diy/caltex-5l-motor-oil-2874EA currently on special.

http://www.caltex.com/za/products-and-se...ants/delo/

You want the Delo 400 multigrade , not the gold or the LE.

I am also looking at some of the oils from the Motul range as they also produce excellent lubricants, this one in particular

 https://www.motul.com/za/en/products/oil...sity%5D=32

[minion]

Good to know ... was wondering what oil to get for the mini...

How does it compare to shel helix HX5? (yellow can)

[DomMINIque]

Boyscout, they were having this discussion on whatsapp the other day and said that maybe that motorbike oil was something to look into as they also having similar characteristics to the a series (I'm assuming shares the oil with the gearbox.)

I'm way out of my depth here, just playing broken telephone.

[Vinay-RS]

Deon, thanks for writing this up with your own personal experiences. Abri and I have been chatting about what oil to use and there were a couple of suggestions based on a couple of key issues. One was that the oil needed a high ZDDP content and the other was that viscosity modifiers did not work well with the harsh environment in the gearbox and thinned a lot over time, reducing the efficacy of the oil, suggesting the use of a monograde oil (i.e. SAE 40) instead of the standard 20W50 that is usually recommended.

These were the two articles that were shared with me were:
http://ratwell.com/technical/OilSelection.html#advice

http://www.upmpg.com/tech_articles/motor...index.html

Another suggestion made by a mini owner who works for an oil company was Fuchs oils. They had a diesel oil that was highly recommended, due to a high ZDDP value and had a similar viscosity. Also unlike some companies they were willing to provide the ZDDP contents of their oils.

[Boyscout]

Motorbike oil could be a good alternative, as motorbikes also share the transmission with the engine oil. However, as motorbikes have a wet clutch, the oil has to be specifically designed to have low zinc content as to not interfere with the clutch operation. So while it probably has the characteristics to deal with transmission loads, it may not be suitable for the flat tappets in the A-series.

As far as the Helix HX5 is concerned, it is a very good oil from a reputable company, however as it is API SN rated it may not contain enough ZDDP. ZDDP concentrations have been systematically reduced since the SG rating. SF was the last oil that had relatively high levels of Zync.

Even in diesel oils the ZDDP levels have been reduced to cope with particulate filters so using diesel oils is not always a guarantee that concentration is high enough. From what I could find out, Delo 400 still has high levels of ZDDP.

Now there is a school of thought that ZDDP is only applicable once the film strength of oil has been breached. In this case the ZDDP works as a barrier to prevent metal to metal contact in high pressure situations such as the gear to gear and cam to follower areas. With modern synthetic oils the film strength is vastly improved, so it is quite possible that the extra protection of ZDDP will never be needed.

For my own piece of mind I use the Delo400 as it's film strength is comparable and sometimes better than full synthetics and it has the added ZDDP, so IMHO it is like wearing belt and braces.

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http://www.fuchsoil.co.za/automotive/gra...tra-20w50/

This looks like a good oil as it is API SG. I would still prefer a lower Cold rating such as a 10W or 15W but that's just me

[Jared Mk3]

Thanks for putting this up

[Boyscout]

Interesting observation around the use of multi grade in the Mini regarding the high shear in the gearbox. It is definitely true that it stuffs up the multi-grade oil due to the breakup of the friction modifiers, the stuff they add to make an oil multi-grade. It makes perfect sense. In one of the write-ups I found on the inter-web they actually refer to the A-series as fitted to the Mini as a case in point.

Now you can get Delo Silver SAE40 with a good dose of ZDDP. I just don't know what the effect on cold start will be.

[Vinay-RS]

Any idea what the actual ZDDP content is in the Delo Silver SAE 40? It might be useful to create a table with oils that are suitable and their ZDDP contents.

[Boyscout]

Delo Silver SAE 40 = 0.06% (600 ppm) from their web page https://cglapps.chevron.com/msdspds/PDSD...Format=PDF so it is not that high really
Delo 400 Multigrade = 0.15% (1500 ppm) from https://cglapps.chevron.com/msdspds/PDSD...Format=PDF now this is a good level

From reading up on oil shear and modern oil stability I will stay with Delo 400. It has a very good level of ZDDP and I have had good experience with it. The only negative issue could be that due to a the high detergent action this oil has, it may dislodge or dissolve deposits in old engine and could cause leaks on old seals. My engine is still fresh so I haven't had any issues.

[Vinay-RS]

I spoke to someone from Castrol and the figures for both GTX HM 20W50 and SAE40 are lower:

Castrol SAE 40 = 0.11% (1100 ppm)
Castrol GTX High Mileage 20W50 = 0.10% (1000 ppm)