Used to get engine bay washed from service station, but no more and no oil shoukd be used to wash engine bay. After about a month I use a blower to bliw of dust and occasionally use a paint brush. Also use fine mist of waterless wash and wipe it off with microfiber towels.
Down the road I will use engine degreaser and wash it down with normal garden hose.
Washing from service station does not normally cause any issues. I have been doing it without covering ECU or generator, but now I sm just becoming more careful.