Classic car engines and Synthetic Engine oils - OK or not?
Discussion
I have a 1969 MG Midget Mk III with a 1275 cc A series engine. The engine is being replaced with a new recon unit by the MGOC Workshop. Question is: what is the best engine oil - regardless of cost - to use to get easy starting, engine protection, and long life - so-called "Classic" oil like 10W/50 mineral oil, semi-synthetic, or the best modern full synthetic like Mobil 1 0W-40? Hours of research including advice from experts at MGOC, Castrol, Mobil, Opie Oils and online forums and blogs yield complete contradiction ranging from "must use old-type mineral oil or your engine will vapourise in a puff of smoke" to "ignore all the old wives tales - use the best hi-tech full synthetic". I have clocked all the arguments about old engines' operating characteristics, seals and gasket compatibility, clearance, contaminant suspension, Zinc additives or lack of, splashability, film adhesion, and a host of other things. What is the best, most authoritative advice on this clearly contentious issue - and please state your sources/justification/qualification.
Ferry said:
I have a 1969 MG Midget Mk III with a 1275 cc A series engine. The engine is being replaced with a new recon unit by the MGOC Workshop. Question is: what is the best engine oil - regardless of cost - to use to get easy starting, engine protection, and long life - so-called "Classic" oil like 10W/50 mineral oil, semi-synthetic, or the best modern full synthetic like Mobil 1 0W-40? Hours of research including advice from experts at MGOC, Castrol, Mobil, Opie Oils and online forums and blogs yield complete contradiction ranging from "must use old-type mineral oil or your engine will vapourise in a puff of smoke" to "ignore all the old wives tales - use the best hi-tech full synthetic". I have clocked all the arguments about old engines' operating characteristics, seals and gasket compatibility, clearance, contaminant suspension, Zinc additives or lack of, splashability, film adhesion, and a host of other things. What is the best, most authoritative advice on this clearly contentious issue - and please state your sources/justification/qualification.
Ah, oil threads...I was particularly amused by somebody on a LR group on FB the other day, swearing blind that anything thinner than 20w50 was FAR too thin... which is why he used SAE30...
If you are concerned about zinc levels, Mobil publish the levels across their range of oils which shows up quite a difference.
https://mobiloil.com/~/media/amer/us/pvl/files/pdf...
I've used Mobil 1 in my Lotus TC engines since, well I'd guess the 80s, but that has the cams/tappet buckets running in oil so it's obviously different from the A series. The trouble is that specs change over the years, so Mobil 1 today is probably different from Mobil 1 in 1985, and I'd guess the same is true for other manufacturers.
In your shoes I'd look for something with Porsche A40 spec - if you look at that page they seem to go for high Zinc level oils in their A40 spec.
https://mobiloil.com/~/media/amer/us/pvl/files/pdf...
I've used Mobil 1 in my Lotus TC engines since, well I'd guess the 80s, but that has the cams/tappet buckets running in oil so it's obviously different from the A series. The trouble is that specs change over the years, so Mobil 1 today is probably different from Mobil 1 in 1985, and I'd guess the same is true for other manufacturers.
In your shoes I'd look for something with Porsche A40 spec - if you look at that page they seem to go for high Zinc level oils in their A40 spec.
I had this dilemma myself: I wanted to use modern oil but.... so research and research until I was dizzy. As said, I needed ZDDP and the experts on forums said 'NO!' to new synthetic stuff.
So I did more research, asked Opie, Mobil and then got the facts and figures and Mobil 1 0w40 has 1100ppm of zinc whic is plenty for flay tappet engines, thank you and good night!
So now the old girl runs on Mobil 1 and she appears to be a happy old lady with higher oil pressure, quieter tappets (hydraulic) and she runs cooler.
So I did more research, asked Opie, Mobil and then got the facts and figures and Mobil 1 0w40 has 1100ppm of zinc whic is plenty for flay tappet engines, thank you and good night!
So now the old girl runs on Mobil 1 and she appears to be a happy old lady with higher oil pressure, quieter tappets (hydraulic) and she runs cooler.
b2hbm said:
I've used Mobil 1 in my Lotus TC engines since, well I'd guess the 80s, but that has the cams/tappet buckets running in oil so it's obviously different from the A series. The trouble is that specs change over the years, so Mobil 1 today is probably different from Mobil 1 in 1985, and I'd guess the same is true for other manufacturers.
It certainly is different to the original Mobil 1 of the 1980's, and why I stopped using Mobil 1 in my Sunbeam-Lotus by the mid 90's.......way too thin by then.I went back to using good old Valvoline Racing 20-50.
I worked in the historic restoration business for some years and the only thing I remember about this issue was that the most important factor is the diameter of the oil pickup pipe in the sump. Older cars tend to have bigger pipes which are fine with thick old fashioned oils but can sometimes struggle to pick up the modern thin oils. I should have thought that if the pressure gauge shows good pressure when hot then you would be better off with a synthetic oil which has higher film strength and better cooling properties. Do not go too thick though as this can slow the flow through critical areas like bearings which can cause the oil to boil as a result of staying to long there and getting too hot. It has to be thin enough to flow properly and carry the heat away from the bearings.
duka said:
My previous A-series stuff I've used both Valvoline Racing 20-50 & also Castrol R on one engine - both good
Plus 1 for Valvoline, which has high zinc.But I run in my engines on the cheapest supermarket oil I can find - I'll throw it away after less than 500 miles, no need for all the detergents etc
I used to add to that a 'breakin additive' with extra zinc, but they have got very expnsive lately, and one of the makers, Lucas US, has a ready-mixed version that woerks out cheaper! https://www.ebay.co.uk/i/162552173092?chn=ps&a...
John
No connection etc.etc.
It's my understanding that much of the answer to this is dictated by the oil filtration used by the engine. If your rebuilt engine has a nice modern type paper cartridge oil filtration system, you are good to go with modern high detergent synthetic oils in a suitable viscosity for the application. If you have old fashioned gauze filtration, you stick with a straight weight mineral oil. The reasoning behind this was to do with particulates in suspension and the capability of synthetic vs mineral oil to hold particulates in suspension - synthetic oil being very good at it. This is great if you have good filtration as all the combustion by-products and microscopic wear particles get held in the oil, circulated around to the modern filter whereupon they get filtered out and the clean oil sets off around the engine again to do its job. If you DON'T have good filtration those particles remain in the oil and circulate around with the 'clean' oil, making a more abrasive lubricant that wears bearings faster and exacerbates the problem...... which is where you want the old fashioned straight weight oil as it has far less detergent and far less ability to hold particles in suspension, so they settle out into the sump whilst the oil waits to be pumped back around the engine. That's the theory I was told by more than one engine oil manufacturing company when I was researching it.
However, in new applications (like yours) where an engine is freshly rebuilt so you know that the inside of the engine is clean and there aren't historic combustion and wear deposits lurking to be washed away and held in suspension by a high detergent oil, you can move to using a fully or semi-synthetic to take advantage of the higher specification of those newer lubricants. Ideally this would be coupled with modern spec, full flow filtration. The advice I received was to avoid going too thin as tolerances on older machining and seals was not up to standard to retain very thin modern oils without increased likelihood of leaks. Ultimately it came down to you pays your money and takes your choice, but filtration seemed to be a significant determining factor.
However, in new applications (like yours) where an engine is freshly rebuilt so you know that the inside of the engine is clean and there aren't historic combustion and wear deposits lurking to be washed away and held in suspension by a high detergent oil, you can move to using a fully or semi-synthetic to take advantage of the higher specification of those newer lubricants. Ideally this would be coupled with modern spec, full flow filtration. The advice I received was to avoid going too thin as tolerances on older machining and seals was not up to standard to retain very thin modern oils without increased likelihood of leaks. Ultimately it came down to you pays your money and takes your choice, but filtration seemed to be a significant determining factor.
larrylamb11 said:
The advice I received was to avoid going too thin as tolerances on older machining and seals was not up to standard to retain very thin modern oils without increased likelihood of leaks.
This is one reason why I stopped using Mobil 1 in my Sunbeam-Lotus when Mobil 1 when it went to 0w......it was just way too thin, and in a canted engine with DOHC with individual cam covers that retained oil above a gasket joint........ 
Plus the well known 907/911 engine builders of the day still recommended Valvoline Racing anyway, even on a freshly built engine.
Maybe placebo effect, but engine did seem to run 'sweeter' on the 'old fashioned' Valvoline Racing than on the newer Mobil 1.
The guy that I worked for who was very very good with old engines always maintained that decent 20/50 was the way to go . Modern synthetic always led to leaks as older component tolerances were a bit lax .
The management of warm up on older engines and sympathy of use is the main key in engine life .
The management of warm up on older engines and sympathy of use is the main key in engine life .
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