Break-in additive
 

'morning,

Some years ago I read about modern oils lacking Zinc (ZDDP) due to modern cars catalytic converters. I bought some break-in additive with the intention of adding some at every oil change promptly forgetting about this after the first one.

I just saw something online about synthetic oils being even worse for old engines purely because of the lack of ZDDP, so synthetic oils are still better than mineral but only provided you add the break-in additive yourself.

So, does anyone here do that?

Regards,
Henrik Morsing

The Zink is only needed for pushrod engines.

However with a freshly built engine it is good for the break in stage but after that ohc engines do not need it

That's wrong, depending on what you mean by "needed". And not really sure what push-rod would have to do with it, do you mean flat lifters?

Regards,
Henrik Morsing

I know the zink part is not what does the work but that is what the marketing pushes is the zink side.

Pushrod engines (flat not roller bearing lifter) have high pressures and tend to need the higher zddp content

Most older engines surely have the same basic tappet arrangement - the camshaft pushes a flat surface of some sort which then pushes either a pushrod or the valve itself. If the valve spring has the same strength then the scraping action of the camshaft lobe on the flat surface will be the same?

Some more modern designs have a roller which runs on the camshaft lobe, so the friction is reduced. But no 240s?

Rocker shafts on pushrod engines are geared. You also have the weight of the pushrod and follower acting on the cam and the face is much smaller

I think maybe there's a distinction between "needed" and "beneficial" to be made here.

Modern car makers don't care if their cars last more then 100 000 miles, but as a classic car owner, I do. I don't mind adding some additive every oil change and I think it will make a difference to both rings/cylinders and cam followers.

That said, my cam follower gap hasn't changed in 250 000 miles but two of my cylinders are leaking air past the rings now.

Regards,
Henrik Morsing

They have gone to design them to fail at about the 100k now.

The reason for the change in oil is emission control, the cat is poisoned by the oil additives hence changing engines and oils