It depends on how you use the engine. Obviously, picking its best move or nearly best move when they're close in value, will get you caught. But suppose you sa

It depends on how you use the engine. Obviously, picking its best move or nearly best move when they're close in value, will get you caught. But suppose you sample from the engine's ranked moves to have some decent ACPL (average centipawn loss) error rate. Just a slightly lower rate than you'd have on your own. If you further bias your sample to moves to that look reasonable to you, then I don't see how you'd get caught. Current engines may not have the right support for such sampling, but it wouldn't be hard to implement, e.g. with a private fork of Stockfish.