I think you really have to look at the supply/demand aspect of oil changes. 99% of people are going to need an oil change sooner or later, but there is alot of availability to take care of that. NOS50 makes a good point on the aspect of how much it would really cost.
Places such as Jiffy Lube, get by, by offering the "upsell". If they strictly sold oil changes, they probably would not be in business.
I recently heard of this same type of business rolling around town.
I would try to think of something that sets you apart from the rest. What does no one have in the oil change industry, that you could do.
-You could tag team up with a detailer or possibly a dent puller and while their pulling dents or buffing things out......you change the oil
-Try to hook up with a small business, change their oil and give them a group discount or special "company" rates
-Tag team with "valet" services, and when they take the keys, they could offer them an oil change while they shop or eat
Everyone and their mom offers the service of an oil change.....think about the added service aspects that you could at to the current situation to define your current market niche. Make it your own and make the best of it. And remember, Rome was not built in a day.