a little off for some groups: 1989 Mazda 626 clacking from top of engine

We went through this a few months ago. I'm much too lazy to do it again.

JT

Basically in this case diesel lubes still have zinc based EP additives which have been absent in the s rated oils for some time.

Well, once it fianally STOPS snowing I'll pull of the valve cover and have a look. I have a Supra I use in the summer, the Mazda's a winter beater. When the Supra goes on the road I plan on giving the Mazda a better going over than I did in December when I bought it. But the forecast is for more snow this week.

And the funny thing is, I drove it about 20 miles yesterday, no problem. This afternoon it fired up just fine, I drove it about 7 miles and the ticking came back. I stopped for a cup of coffee, and the next three times I started it, it ran fine.

So, I guess the cover comes off in the (real) spring...

Give it time. Change the oil, and put in a bit more MMO. The crap doesn't all come out at once, and it's crap that's causing the problem. You can safely use a bit more the second time - but no more than 1/2 bottle per 4 quarts (about 12-15%) on a dirty engine. Change oil again in no more than 2000 (prefer 1000) miles. THEN pull the cover and have a look. On the Supra it's a good idea too, to keep the chain tensioners working.