Stopping a tappet rattle - ATF???

Yep, 'twas me that suggested it and ATF I suggested.

Why not just throw in a handful of sawdust or an egg or something?

Fix it properly. If you alter the oil significantly off spec', which adding ATF will probably do, then you'll mess up the lubrication of some other critical engine component which only just gets enough oil as it is.

Then there's the additives. What'll they do to each other?

What's the viscosity of ATF anyway? A quick Google returns something like

Don't do it! Fix it properly.

We're only talking about adding 500ml to a crankcase full.

The anti-varnish additives in ATF help free up sticky hydraulic tappets

- it only needs to be done the once, and solves the problem for a fair while. It doesn't seem to have any negative effects - oil pressure stays fine.

ATF is about 10 weight.

ATF at 80w100? I think not. You could try running your auto box on something that behaves like treacle at normal temperatures, but I doubt it would work properly.

Alex

which

something

Yes, and around [a light] 75w/80 transmission weight. It should certainly work to some extent. I would certainly prefer to try ATF than chainsaw oil suggested by someone in a current conversation in the mercedes newsgroup. ATF is also great as an *occasional* diesel fuel additive, as I have mentioned somewhere, also due to the same inherent properties, at about a litre to every 100 of diesel in the tank.

Huw