From my perspective, mistakes are excusable, especially if they're "owned up too". But you first have to give them that chance. No body wants to be accused of knowingly screwing something up and trying to hide it.
As a punk 15 year old back in the 60's, I got to be a grease monkey at a Sunoco station and I was really proud of my ability to get that job and learn. Typical 3 bay garage with small waiting room, desk, big bulky credit card machine and cash register. This was back before self-service, and every time a car came in and tripped the bell you'd run out and do the whole full service thing. Windshield, check oil and washer fluid, and fill-er-up. After some time on the job I got "checked out" on oil changes and grease jobs in bay #1 but still had to answer the bell in between and sometimes around rush hour traffic it could take an hour to complete the oil change. Bay's #2 and #3 were where the real mechanics worked.
One day I was so excited that my boss and the owner, Leonard, was out on an errand and a guy came in with a 67 Vet stingray with a 427 and wanted an oil change! OH BOY! I'm doing some stuff now! I was extremely careful getting it up on the lift and got the plug out and then the traffic hit. I was running like the proverbial "monkey handling a football" My boss came back after a while and saw I had a Vet in bay #1 and said, "what are you doing"? I said "changin the oil, but man these new Vets sure take a lot of oil don't they" His eyes got huge! "Like, how much"? I said, "well I've put 13 quarts in her and it's not on the dipstick yet"

I was so busy I never got around the other side of the Vet to see the floor of bay #2 and#3 completely covered in 30w oil.


Leonard was a great guy and boss and just shook his head and chuckled. I spent the rest of that night cleaning my mess but I ended up a pretty darn good mechanic and machinist. I don't want to believe there's a difference in the kids these days. Sure they have way more distractions and privledges, but that's what our parents said about us too?
That being said, I'm pretty careful about who I let do what on my vehicles and more often than not would rather do it myself just to make sure it's right, and still I make mistakes.
