Tell me what you think of this formula, and if it is wise to use in deciding what car to buy. I am using 200,000 miles as "the life of a car". And taking the cost of a car divided by how many miles it has left until it reaches 200,000.

For example:
a 2007 911 Cabriolet (with 0 miles) = $83,000 / 200,000 miles = $.415 per mile.

a 2004 911 Cabriolet (with 12,472 miles) = $66,000 / 187,528 "remaining miles" = $.351 per mile

a 2002 911 Cabriolet (with 32,845 miles) = $42,991 / 167,155 "remaining miles" = $.257 per mile

a 2000 911 Cabriolet (with 46,000 miles) = $31,900 / 154,000 "remaining miles" = $.207 per mile

I know that a used car will need more maintanenace than a new car -- I gues my argument (to myself) is that if you keep the new car for 200,000 miles you will eventually incur the same issues. Tell me what flaw is in this formula. According to the data I have found, the older car seems to be the better choice. And I know that a 2007 '997' is a better car than a 2000 '996'... For this formula I guess I am ignoring that.

 

well the first 'flaw' I can see in your formula is that the cost per mile is not the same throughout the life of the car. it starts out low, and then increases more steeply with each increment of x (time)

if you are familiar with the depreciation curve for cars, then this is kind of the opposite

 

I am not thinking "operating cost" when I say cost per mile -- I am thinking original cost (i.e. purchase price only).

 

If you are not including maintenance costs, why are you even bothering with simply the mileage? It won't provide you with any metrics that really matter alone. All cars may incur the same maintenance over 200k miles, but you're paying all the maintenance for less miles on some, thereby increasing the cost per mile quite a bit.

 

good point.

I guess what I am trying to figure out is at what point does,"paying all the maintenance for less miles" push the price per mile over the inital savings of buying a car with more miles.

I know this is impossible to do with out knowing what the maintanenace cost are going to be... I'm just tring to create conversation.