I am so confused by the info below that I got from the internet, but it souonds technically pretty cool - don't use ATF fluid.

See below...

> *** However if one fills the canister of the fuel filter with ATF when
> changing filters - then one gets 100 % ATF - undiluted !

But the higher concentration is only working for a few seconds (until the filter has
purged) and, as I said in my earlier post the dispersant additive just isn't that powerful
anyway. I believe that what is actually happening in this situation is related to the fact
that ATF is something like 100 times more viscous than diesel. I suspect that when ATF
hits those tiny injector orifices it literally blasts any deposits out of the way.
Although I've never tested this hypothesis, I think that you'd get the same results from a
filter full of an ISO VG 32 pale oil (same viscosity - no additives at all).
>
> ATF is high in the aromatics - all of which are good cleaners ... but
> which have been removed from most diesel ..
>
Actually, ATF has a small proportion of napthenic base stock in its make up which is
different from most automotive/heavy duty oils which are almost entirely paraffinic in
composition*. The reason for that is that the napthenic component imparts a small amount
of swelling to certain rubber seals in an automatic transmission. While it could be said
that 'napthenic is to paraffinic' (lubricants) as 'aromatic is to aliphatic' (solvents),
it would be an exaggeration to describe napthenic oil as being a "cleaner". In any case
the proportion of napthenic base stock in ATF is fairly small since napthenics are not
very good as lubricants and are somewhat more prone to oxidation. I don't know the actual
percentage but if ATF had a high amount of napthenics we would be changing the
transmission fluid in our cars almost as often as the motor oil.


*A bit of speculation: I think that the "high mileage" motor oils that have recently come
on the market have a bit of napthenic content for the same reason that it's put into ATF -
seal swell and, in this case, to counteract seal shrinkage from a lifetime of being
exposed to nothing but paraffinics.