[FRS Dad]

I did misread (and misquote) the question. The guy I sourced was asking if his engine would have been damaged by adding some ATF fluid to his existing motor oil. It was not a case where the crankcase held nothing but ATF. I stand corrected.

I had a chance to roundtable the issue with the owner of a respected indie shop here and a couple of his techs. All were fascinated as to how the shop managed to screw up an oil change so badly. That aside, the consensus was that if the duration was short, and the owner saw no smoke and didn't get an oil pressure light, no permanent harm done. ATF is not the right petroleum based lubricant for an engine but it is still a petroleum based lubricant.

I asked about the wisdom of pulling the heads and inspecting the cylinder walls for scoring or burning. The consensus here was that the engine is so precisely built with such tiny tolerances, opening it up for exploration would probably result in more issues than the ATF mistake caused. They stated if the engine was torn down you'd likely find it to be unusually clean but undamaged.

With respect to mitigation and the owner's understandable anxiety, they felt that complimentary oil changes and the extended warranty were appropriate.

The shops owner addressed the issue of getting bigger damages ( a new engine, a replacement car). He pointed out that no dealership or shop is going to voluntarily replace an engine or buy back the car because that remedy is so disproportionate. A law suit would be required, and he felt that the mediator and the judge would find the extended warranty to be fair compensation.

With respect to future work, the consensus was that the OP's car was going to get the star treatment here on out and is probably the safest place for future oil changes and general maintenance.