You can write this into ratio form to help explain this. The ratio 4:2 can be used to explain this problem with the 4 meaning 4 oil changes and the 2 meaning after every two hours. You want to make it to where the 2 hours is at 8 hours so you would multiply 4 on both sides of the ratio which will give you the new ratio of 16:8. The mechanic can do 16 oil changes within 8 hours.
