Ihave been researching the zinc dilemna for a while now, and what I did find out is racing oil has low levels of detergents due to the fact the detergents reduce the shear strength of the oil. So if you do use a racing oil you need to change the oil more often. I also found that the SM oils have a maximum of .08% of zinc, which would be fine for lifter foot pressures of 600 pounds. (which was the limit of the testing device being used in the particular test) However this is the MAXIMUM level of zinc allowed and some are down to 04% which isn't adequate for a flat tappet cam. I have only been taking notes of studies done by reputable agencies, such as the fella from GM that wrote a rather informative article, who it turns out is nearly without peer in the lubrication world. But what ever the case. about the only consistency I could come up with was around 1200 ppm (where that lies in percentage I don't know, that was another problem I was having, half the studies were done in PPM and the other half in percentage)of zinc should do you just fine. There has been sqawking about just using oil for diesel engines, that has its problems as well, since the oil is formulated for diesel engines after all. (one issue is the extremely high level of detergents) But it does have adequate zinc levels for now. but that will probably change soon as the EPA is requiring catalytic converters on trucks. (that is why I got laid off from Kenworth, no one was buying the new trucks with all the emission junk on them) what ever the case you need an oil with at least .08%/1200 PPM zinc and since everyone has used pretty much every weight oil known to man with what seems like the same results. just go ahead and use whatever you want. (just to add to your list, 5w-30 is what I have been using for the last 3 years in my 216) Just for fun, start looking at oil formulation. That is some black science, look up the various ratings SL, SM and what have you and it gives you the min/max of various components, I'm thinking you could spend at least two years in college learning all this nonsense. What ever the case there are a few companies making oil for classic cars, castrol is the only one that comes to mind right now. As far as lubricity, there will be arguments of course, but synthetic is by far superior to your standard mineral oil based oil. Oh and one last thing, the zinc and phosphorus will be somewhat relative as the P in ZDDP is phosphorus. which in itself is an EP additive, there is also moly and boron being phased in, to replace the zinc (converter poison)
Last edited by brokenhead; 11/08/2011 1:05 PM.
