Do you work for free?
Yes if I own it.
Changed the oil in a semi truck just today.
Nobody walked up to me after and handed me money.
I changed the engine oil, oil filter, coolant filter, both fuel filters, greased it, new front tires, checked it all over, replaced a marker light bulb, a headlight bulb, swapped the DPF out with a clean one, checked the air filters, blew them out and put them back in, replaced the turbo, checked the brakes, and pulled it outside and took it for a 15 minute test drive. One of my summer students detailed the interior, and cleaned the windows and mirrors while it was in the shop, then she checked the 12 rear tires condition and psi. I had to change 1 rear tire with a badly cut sidewall she found.
When i came back from my test drive 3 of my summer students washed the exterior.