I don't think you will find temperatures much in excess of 300F in the air end - unless there's a mechanical problem as Bob alluded to. Then oil is the least of your problems.

Why not just use the Interlube synthetic air compressor oil, made for the purpose, rather than try your luck with ATF?

dave

SP 3420 operated in the same type of enviornment as the 3751 and 2926 copuld operate in and we used Carbonless air oil that worked fine The only air system that I saw carbon up were on the NN that could have been fixed by changing oils. A good proven oil that someone has used is all you really need.

Robby

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Whenever I've made a brake application on the real Thomas it smells like a pine tree or gin. It smells much better than Estrolene, which is what we use at Greenfield Village.