What 20/50?

[Perseverant]

Probably not a new question. I'm about to do the annual oil change on my XK120. I don't do as many miles as I'd like as my wife is not too well these days. I've often used Castrol and other well known brands, and when I first got the car a local factor gave me a pretty good deal on Miller's - a bulk 40 litre drum as I recollect. Looking online shows quite a range of prices and some less well known (to me at any rate) makers. During lockdown I bought decking oil from Smith and Allen, which did the job fine and I also see 20/50 oil from them. I just wonder if anyone has any comments?

[Riley Blue]

Following a recommendation by a local MG specialist I've used Millers Oils Classic Pistoneeze 20w-50 in my Riley for around 10 years with no problems, remarkably the engine is still oil-tight too. I've had no reason to change so don't know how it compares price-wise with other lubricants.

https://www.millersoils-shop.co.uk/classic-pistone...

[j4r4lly]

Ive been using Valvoline 20/50 in my 1983 Capri 2.8 injection for the past 12 years.

https://www.ebay.co.uk/itm/225181027793?chn=ps&amp...la-1816181029379&abcId=9303860&merchantid=428632137&gclid=CjwKCAjw1t2pBhAFEiwA_-A-NFjUBvQjLsQD6SJqm28ASFUw3zbrdk_1L4N1hQZyqRR5Ax9PAb1YexoC3YgQAvD_BwE

[tog]

My Bristol specialist always preferred Valvoline Racing 20/50 too.

[roperrich]

More recently I've been using Valvoline VR1 20/50 which seems to work well and is easy to get hold of. I've also recently tried the classic Halfords 20/50 oil, I didn't expect much but the car really seemed to like it, so would use again. I'm also using an additive - Ametech oil treatment. This is the only additive I would highly recommend and have been using it for about 10 years. If you want the highest quality options ring Anglo American oil company in Poole, I've used their engine, gearbox & differential products and they are probably the best on the market.

[sixor8]

I needed 20w/50 mineral oil a couple of years ago for an old car and what irked me was that it was more expensive than synthetic or semi-synthetic oils in the 10w/40 or 5/30 range. Less demand I suppose.

[OutInTheShed]

roperrich said:

More recently I've been using Valvoline VR1 20/50 which seems to work well and is easy to get hold of. I've also recently tried the classic Halfords 20/50 oil, I didn't expect much but the car really seemed to like it, so would use again. I'm also using an additive - Ametech oil treatment. This is the only additive I would highly recommend and have been using it for about 10 years. If you want the highest quality options ring Anglo American oil company in Poole, I've used their engine, gearbox & differential products and they are probably the best on the market.

How could you tell the car 'liked it'? Happy face radiator grille?

[Lotobear]

I've always used Halfords Classic 20/50 in my Lotus twincams and had zero issues - it's pretty cheap and so I just used to change it every year regardless of miles covered. It will be made by one of the big firms, Comma perhaps?

ISTR it has the correct level of ZDDP which is critical to protect the cam lobes in a LTC. Given the similarities (hemi/OHC) between the LTC head and the Jag I imagine it would be a good choice

[Julian Thompson]

The way this works is that the first number is the actual weight of the oil - in this case it’s a “20” weight oil when cold. That’s thicker than a “10” or a “5” or a “0” weight oil.

The second number is the “resistance to thinning” index of the oil. It is not related to the first number. As the oil gets hot it thins out - the second number determines how well it retains its viscosity. So in this case “50” indicates a very high resistance to thinning out when hot, whereas a “40” or “30” as your second number shows that the oil will run much thinner when hot.

Hope that helps.

[mph]

Lotobear said:

I've always used Halfords Classic 20/50 in my Lotus twincams and had zero issues - it's pretty cheap and so I just used to change it every year regardless of miles covered. It will be made by one of the big firms, Comma perhaps?

ISTR it has the correct level of ZDDP which is critical to protect the cam lobes in a LTC. Given the similarities (hemi/OHC) between the LTC head and the Jag I imagine it would be a good choice

Unless they've changed the formulation recently Halfords 20/50 definitely does not have the recommended level of ZDDP.

Millers, Heritage (Fuzz Townsend) and several others are ok. Even Duckhams 20/50 Classic.

[Sebring440]

mph said:

Unless they've changed the formulation recently Halfords 20/50 definitely does not have the recommended level of ZDDP.

Why do you say that? And what is the "recommended" level of ZDDP?

[timster]

I use oil from these guys

https://www.smithandallan.com/product/smith-allan-...

I paid £34 delivered for 10 litres

[dr_gn]

It’s a bit of a pointless question really, unless you’re asking for scientific tests on a particular engine which is of a particular mechanical standard.

You could put the most expensive or cheapest 20/50 over multiple brands in your engine, and have absolutely zero objective clue which one is ‘better’.

Sure, you might get some highly subjective answers, and some anecdotal ‘evidence’ about oil pressure or noise, but none of it will necessarily apply to your car in terms of which is the ‘best’.

[mph]

Sebring440 said:

Why do you say that? And what is the "recommended" level of ZDDP?

I've read several articles on classic oils and Halfords is one of the brands that don't (or didn't) have the generally accepted levels of ZDDP.

The recommended level is between 1000 and 1400 ppm.

This article from Duckhams is quite informative.

https://www.duckhams.com/zddp-what-does-it-all-mea...

Heritage Oils, with the Fuzz Townsend connection, also have a bit of info.

https://motorspirit.co.uk/product/heritage-20w-50/

Edited by mph on Sunday 5th November 10:00

[rovermorris999]

Another vote for https://aaoil.co.uk/
High levels of ZDDP and the 'classic' oils also have US military spec long term storage additives which is ideal for cars that get little use. Perhaps other oils also have such additives but I've not seem them promoted.
Not the cheapest though.

[aeropilot]

tog said:

My Bristol specialist always preferred Valvoline Racing 20/50 too.

Yep, I always used to use Valvoline Racing 20/50 in my Sunbeam-Lotus as well, highly recommended.