Oil for Jowett engines

[David Morris]

Hi all,

I realise that this may be a contentious subject, that has probably received much attention in previous discussions?

It concerns our choice of lubricating oil for our engines. When entering a parts store, we have a huge choice of engine oils on the shelves. One common thread is that modern vehicles, with catalytic converters, now need oil that doesn't contain zinc, as this has been found to adversely affect catalytic conveters, so has been removed from modern oils.

However, our engines, with their flat tappets, desperately need the zinc component to minimise wear. So, my advice is to steer well clear of modern oils. Some oil suppliers sell 'Classic' blends, and these probably contain a zinc component, but it's worth checking. Personally, and with no wish to act as their promoter, I have used Rock Oil Classic blends, which come in straight SAE 30, 40 and 50. It's a reasonably economic oil and a 40l drum lasts a long time, even in Jowett engines, that are renowned for either burning the stuff or leaking it! Probably both!

All the best,

David

[Forumadmin]

For flat tappet engines e.g Jowett you need zinc but not over a concentration of 1400 ppm, around 1000ppm is best. Use an oil that is specially formulated with zinc rather than using an additive. Multigrade oils are good if you are using in a variety of conditions and are generally better than straight 30 sae.

The main effect of lack of zinc is worn camshafts. Do not assume because it is marketed as Classic it contains ZDDP.
https://rislone.com/blog/engine-oil/the ... r-engines/
https://bobistheoilguy.com/forums/threa ... on.350037/

Also put ZDDP into search box and you will get lots of hits on views by contributors.

[David Morris]

Hi All,

I have contacted Rock Oil, to see what is their level of ZDDP in their Classic 30 oil.I agree that the term 'Classic' on a tin of oil doesn't mean it has the right level of ZDDP. Always to check on the tin, or ask?

All the best,

David