When the price of gas increases, Why doesn't motor oil increase too?

Oil changes for my car are always the same price... Whereas gas is always changing. I thought gas and oil come from the same place but are process different.When the price of gas increases, Why doesn't motor oil increase too?
It does . Where have you been the last 10 years?When the price of gas increases, Why doesn't motor oil increase too?
Which ever is in demand will always cost the most.It could be water someday.Now milk is going up too.
Ok, now you've done it. ';They'; are going to read this and say, ';Hey WE should go up, too.'; :o)