Old Cars with flat tappet engines - "Classic" Oils

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Tue 28 Aug 2018 19:17
Old Cars with flat tappet engines - "Classic" Oils - edlithgow

Saw this stuff in Halfords,"Classic" 20W50 API SE/CC in a nice tin.

Now I like old thick oil, and I don't discount the alleged downside of newer specs with lower zinc levels. (I use SJ routinely in my 1986 car and would use SG or SH if I had it).

However, I'm unclear what the advantage might be in going as retro as SE, apart from price. I thought this might be priced as a niche product, but it was only 18 quid for 5L IIRC. Quite surprising.

It seems to be a re-branded Comma product, so should be OK, BUT its only got 600-800ppm from a datasheet I saw, perhaps a bit low for flat tappet engines.

www.commaoil.com/productsguide/view/6/262/CLA20505L

The similarly pitched "Castrol Classic" is SF (later, but still not the SG or SH I might expect), and costs nearly 3 times as much.

msdspds.castrol.com/bpglis/FusionPDS.nsf/Files/4E3...f

No info on the Zinc level. Given the niche its aimed at, that's surprisingly coy, even suspect.

This article, written in 1996:-

www.volvoclub.org.uk/castrol.shtml

says "Oils for modern engines comply to the latest API ratings of SG and SH and are ideal for the design of a modern engine, i.e.: use of neoprene seals, high delivery pumps, narrow oil galleries, high revving with overall tighter machine tolerances."

This implies that SG and SH are incompatible with pre-1980 engines.

I wonder why?

With the possible exception of neoprene seals, all those factors would seem to be mostly affected by viscosity, rather than API grade.

Any educated guesses?

Academic at the moment but might get relevent if I move back to the UK and can find and afford an old car or motorcycle.

Edited by edlithgow on 28/08/2018 at 19:19

Reply | Report as offensive | Link
Wed 29 Aug 2018 08:35
Old Cars with flat tappet engines - "Classic" Oils - jc2

In the elderly motors I used to own,it was 20W/50 in the summer and 10W/30 in the winter-both the cheapest I could find.

Reply | Report as offensive | Link
Wed 29 Aug 2018 09:53
Old Cars with flat tappet engines - "Classic" Oils - John F

I bought Wilko's Classic 20/50 API SE CC for my 1980 TR7. The handbook recommends SE spec and for Britain various makes (BP, Castrol, Duckams, Esso..etc) ranging from 15/40 to 20/50. It lives in a cool dry garage integral to the house which probably never falls below freezing so doesn't need reduced viscosity for winter. For overseas the handbook recommends 15/40 or 15/50 for ambient temperatures down to -10C, 10/40 or 10/50 for ambient temperatures down to -20C and 10/30 for ambient temperatures from -20 to +10C. Those were the days of informative handbooks - and British sports cars being sold in USA and Canada!

I think the zinc issue you mention might be important, but don't know why. Anyway, it's a robust engine - didn't need any modification for when unleaded petrol was introduced in the 80s. It would probably be quite happy with gordonbennet's nearly new 10/40...;-)

Reply | Report as offensive | Link
Wed 29 Aug 2018 11:26
Old Cars with flat tappet engines - "Classic" Oils - Galaxy

Millers Oils offer a range of oils suitable for "Classic" vehicles:

www.millersoils.co.uk/pdf/brochures/Classic_Brochu...f

Reply | Report as offensive | Link
Thu 30 Aug 2018 16:33
Old Cars with flat tappet engines - "Classic" Oils - edlithgow

I can see why higher viscosity is better in older engines (and perhaps in newer engines if you want to maximise engine life)

I can also see why newer spec oils with reduced zinc levels might not be good for older engines.

What I can't see is why SE is supposed to be better for older engines than, say SH (the last API spec before they started dropping the zinc level) or later specs which might still have as much or more zinc in them than the fairly low level in the Comma stuff.

There may be something in it, but I'd be more interested if they gave some convincing account of what it was.

The only thing stated that seems to make sense is lower detergent levels, which might be a good thing if coke or varnish is helping seal the engine, but that won't apply to all classic cars.

Reply | Report as offensive | Link
Thu 30 Aug 2018 16:45
Old Cars with flat tappet engines - "Classic" Oils - edlithgow

I can see why higher viscosity is better in older engines (and perhaps in newer engines if you want to maximise engine life)

I can also see why newer spec oils with reduced zinc levels might not be good for older engines.

What I can't see is why SE is supposed to be better for older engines than, say SH (the last API spec before they started dropping the zinc level) or later specs which might still have as much or more zinc in them than the fairly low level in the Comma stuff.

There may be something in it, but I'd be more interested if they gave some convincing account of what it was.

I note that the equivalent Miller 20W50 mentions "full ZDDP" (though a number would be better) and is API SJ, so they seem to agree.

The only specific thing stated in the Castrol blurb that seems to make sense is lower detergent levels, which might be a good thing if coke or varnish is helping seal the engine, but that won't apply to all classic cars.

Reply | Report as offensive | Link