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ZDDP how much is too much?

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I just learned about zddp. Went in to check my valve lash that I thought was getting progressively noisier and found they were all off by 1 thou (all looser than I left them 600 miles ago when I installed the cams). One or 2 of them were off by 2 thou. The cams and rockers looked like they did when I first installed them / nothing jumped out at my untrained eyes as a big concern. Not sure where my 1 thou could have gone I started reading the internet, learned about how the US has made some adverse decisions regarding oil composition and as fancy and as expensive as my standard Amsoil synthetic is, it's short the zddp that my Honda b18c flat rockers like to have. I don't know if this is where my 1 thou went but seemed like I should start using some zddp. I re-adjusted the valve lash and put in a bottle of this Lucas zddp additive and boy did my engine sound quiet again!

The bottle of Lucas additive I used claims to raise zddp levels to 5,000! That seems like a lot given most flat tappet oils that contain zddp contain much less than that. Seems like in this category 1,400 - 2k is the norm for street, 2k for break in, and 3k-4k for race only.

Car does seem very happy with it. It seems it may have even raised my oil pressure 5 psi or so which is kind of interesting. I don't plan on leaving it in there too long, I want to get a proper zddp oil for my flat rockers and stiffer than stock springs but how much is too much? Common sense tells me that 5,000 from this additive I'm running now is probably too much. I'm between Royal Purple HPS which will be around 2,000 and some others which are more in the 1,200 - 1,400 ball park such as Red Line and Amsoil's Z-Rod.

What are the drawbacks to too much zddp for street use aside from increased Catalytic converter wear. I'm pretty clear on that older oils (like when my car was originally made) were meant to keep a cat going up to 100,000 miles and they've removed the zddp so now cats last 150,000 miles. I'm ok with just the 100,000 miles. What are the other risk rewards though? I change my oil at old school 3k mile intervals, I don't need extended change intervals / not too worried about the cost of oil.

A small variation is normal and part of the bedding in process - if they continue to increase the clearances it may be time to investigate further. I don't recall the exact oiling feeds to the valve train on that engine, but modern vehicles normally have a copious supply of oil which means the main reason to use a zinc additive is less significant - it's more for splash lubricated pushrod lifters/followers and some engines that are particularly hard on their valve trains, like the Pinto engine.

The best thing to do is to contact your oil company's tech section/FAQ. For example, you use AMSOIL, and they have a full product line with zinc compound additives.

There are two, related, problems with adding your own anti-scuff products - elevated levels can cuse the oil to become acidic, which corrodes the components, and it also reacts with some of the additives that are used instead of zinc based ones, breaking them down.

The general recommended level seems to be around the 1400-1500 mark, but that's just what the general consensus seems to be.

The Lucas additive is much higher than most seem to recommend, but that won't be a set figure, but when used in xxx amount of engine oil and will vary from that, either higher or lower.

I ended up switching to Redline, so far it seems rather good. Further slight increase in oil pressure and engine sounds quieter yet. I had a nice convo with Dave from Redline, the zinc was something around 1,200, phosphorous around 1,400 and the two D’s I don’t remember. There are some writeups online on plumbing additional oiling to the B-Series heads in a post zzdp world so I think they were designed with the zddp in mind by the engineers. That and the newer K-Series switched to roller rockers which Honda had avoided for years. I’ve assumed they switched to rollers in part in reaction to the changes in motor oil specs.

I wouldn't mind doing some fancy extra oiling work to the head but around here it’s pretty easy to confuse the emissions people with stuff like that haha.