The 'E' Type Forum

Anyone used Westway 20w50 mineral engine oil?
Looks a great spec with a high zinc content of 1500 ZDDP
Conforms to API. CC/SD

Simon

API CC/SD is avery low spec bymodern standards, I'm all for modern oils.

Modern standards, particularly for synthetic oils, are for modern engines with very small clearances compared with those of the XK engine. Simon's suggested oil will do fine

I'm not an expert but it's the viscosity that's important for oilway clearances, if they are both 20W50 they'll reach the same flow & penetration, but modern oils have greater thin film strength under extreme heat & pressure.
Perhaps someone knowledgeable from the industry could comment.

Hi Simon....that oil will be ok for your car....standard 20/50classic car oil as sold by Halfords is always a popular choice.....its cheap.....most companies also off a "classic" 20/50.........especially with tbe low milage most are doing and changing it every year..........our cars dont need a "high spec".......but its up to the individual to decide. ....plenty of info on the forum re oil for anyone that wants to search.......Steve

Well from what I'm given to understand, an additive to oil is essential to provide some anti-wear protection for when the oil film can't - e.g. cam lobes where the oil is both pressured and wiped out of the contact area.
ZDDP builds up a chemical surface layer as a back-up.
About 30 years ago ZDDP was limited to 200ppm max, to avoid damage that it causes to catalytic converters (inevitable mixing of oil in the exhaust, minimal on a new engine, increasing with the miles). My technical knowledge wouldn't extend to quoting the exact API or ACEA spec where ZDDP was reduced, but basically it came in with cats. Other additives were used and metallurgy (esp surface hardening) was advancing so far as to negate the need for ZDDP anyway. Certainly Burton Power (famous for fast Fords over many decades) warn against using an oil of more than 1300ppm ZDDP in a cat-fitted engine.
I wouldn't know for myself if the modern oil additives can do the same job as the ZDDP, but I do know that no claims are made for that, whereas the 'classic' oil producers insist that ZDDP is needed for engines of our era. Morris Oils recommend a min of 500ppm; Duckhams say 1200 is the ideal. So that suggests the modern oils cannot provide the anti-wear protection needed for us.
So when I last bought oil, I went for the Westway 20/50, a simple clear statement of 1500ppm ZDDP, whereas at the time I couldn't find any consistent info from the market leaders. Since then I've found more info and it seems any of the classic oils will have about 1000ppm ZDDP.
I will stick with the Westway and buy any decent classic oil when next needed unless the maker refuses to publish the ZDDP level. I got it from one company simply by phoning their Tech Helpline!