My relative I charge 25 full synthetic,others 30 regular/oil filter,40 for synthetic plus depends on what kind,part of helping out,check, tires,fluids,filters.Reminder
of them checking fluid level monthly,never happens.Not a real money earner,just helping out not to get charge of any extra services on dealer etc.One day when not able to do it then,most of them said don't stop doing it.Yeah getting old and worn out.I dont go more than 6 months that doing their oil change.Local auto store accept used oil.