Personally I always check wheel nuts after I have had tyres fitted etc. Always checked oil on dipstick, air filter, oil filter etc after service (when I once had a service contract and Honda did servicing for a while, won't fall for that again ) - once when I got the car home after a service I dipped the oil and it was black, checked air filter, black with leaves in it - went into house to phone Honda dealer and phone rang- it was them asking me to take my car back as service had not been done, I said I know I just checked the oil - turns out they had cleaned it before doing the service, it had been parked in 'finished' queue and receptionist had called me to pick it up WTF. Call me paranoid but I don't trust anyone who has done work on my car - after all I am the one driving it and I want to know things are OK.