I paid $11,000 for my now 3 year old car when it was 2 years old. I didn't finance it so I didn't pay interest. I average about 35 mpg and drive about 12,000 miles a year. If gas was $4 a gallon that is about $1,412 a year. If I drove 15,000 miles a year that is $1,700 in gas. My owner's manual* says to change the oil once every 10,000 miles or once a year whichever is first. The dealership does that for me for free.
I'd have to drive my car for 30 years to make up the price difference between the cars ($52,000)
If you want to get a luxury car, then get a luxury car, but don't act like you're doing it to save money.
*it is no longer true you have to change your oil every 3,000 miles for most cars.
http://autos.yahoo.com/news/how-do-you-really-know-when-to-c...
http://skeptics.stackexchange.com/questions/4209/is-it-neces...
http://www.edmunds.com/car-care/stop-changing-your-oil.html
http://www.nytimes.com/2010/09/11/your-money/11shortcuts.htm...