After a home and a college education, a vehicle is one of the most expensive purchases most people will make. You'll probably buy several over your lifetime, and unlike a house, selling a used car doesn't return much of your original principal. In other words, it's an important personal finance decision. But do you know how much car ownership actually costs?

There are a dizzying number of factors to consider, ranging from the purchase price of the vehicle to how many miles you drive each year. And don't forget about fuel, insurance, tolls, maintenance, and the like. The calculation seems daunting just thinking about it. Luckily for you, I started the nerdy habit of tracking every single car-related expense when I purchased my car six years ago. Here's what I've learned about the true cost of car ownership.

A salesman handing new car keys to a customer.

Image source: Getty Images.

What's the true cost of a new car?

I purchased my Mazda (NASDAQOTH:MZDAF) 3 brand new for $25,300 in June 2013. The following table shows my cost of car ownership at three separate checkpoints along the way, with some of the important takeaways following.

Metric, Cumulative

Year 6

Year 4

Year 2

Miles driven

60,565

43,917

21,891

Gallons of fuel consumed

2,267

1,637

827

Fuel economy, miles per gallon (mpg)

26.7 mpg

26.8 mpg

26.5 mpg

CO2 emissions

24.7 metric tons

17.9 metric tons

9.0 metric tons

Fuel expense

$6,156

$4,533

$2,696

Maintenance expense

$4,611

$2,421

$918

Total expenses, including car purchase

$44,800

$37,294

$31,434

Cost per mile driven

$0.74

$0.85

$1.44

Data source: author.

Rated fuel economy vs. real-world driving: According to the U.S. Department of Energy, my vehicle is expected to average roughly 27 mpg, based on 55% city driving and 45% highway driving. Just over 40% of all my miles driven have come from long road trips, while shorter trips on highways around town probably nudges that close to the estimated split. The remainder has come from driving in the hilly city of Pittsburgh. Even so, the rated fuel economy is surprisingly accurate in comparison with my real-world results. 

Carbon footprint: I've spewed the equivalent of four African elephants' worth of pollution into the atmosphere in just six years of driving. That's pretty eye-opening, and not something that jumps out when buying a car, probably because emissions figures are given in the very unrelatable metric of "grams per mile." Would more drivers take this metric into account if emissions data were described using more comprehensible terms?

Be prepared: Maintenance is a necessity, but a study from AAA estimates that one-third of drivers couldn't afford an unexpected repair. I've spent about $800 per year on maintenance expenses and routinely set aside about $100 per month so the next mechanic trip is already paid for. 

Fuel savings programs: I've saved $407 through fuel savings programs over the life of my vehicle. That works out to a savings rate of 6.2%, which is better than the cash-back rates of even the best credit cards.

Insurance options: Traditional car insurance isn't optimal for me, because I work from home and expect to drive only about 8,000 miles per year. Luckily, there are now pay-per-mile car insurance companies such as Metromile that take that lifestyle into account -- and the savings can really add up.

Ridesharing comparison: I've spent $0.74 per mile after six years of car ownership. Would I have been better off ditching my car for ride-hailing apps? Not even close. According to data from Ridester and others, the average cost per mile of an Uber (NYSE:UBER) or Lyft (NASDAQ:LYFT) trip is between $1 and $2 per mile. What's more, my cost per mile is likely to fall considerably in the next few years. 

Four dogs in the back of an old truck.

Image source: Getty Images.

The best way to reduce the cost of car ownership

If you're looking to reduce the cost of car ownership, then you're really trying to achieve the lowest cost per mile driven. From that perspective, it helps to know that the purchase price of a new vehicle (or depreciation expense) is the single largest cost of car ownership for many years.

Consider that my vehicle cost a relatively affordable $25,300 brand new, but I'll have to drive approximately 75,000 miles for the purchase price to drop below 50% of total lifetime expenses, including fuel, car insurance, parking, maintenance, registration, tolls, and the like. Of course, more expensive vehicles would take even longer to reach that level. Similarly, buying a used car can be cheaper, but it may not last as long and may be accompanied by higher maintenance expenses.

That means rushing to buy a new vehicle once you pay off your existing ride can be questionable from a personal finance standpoint. Taking care of your car and keeping it for as long as possible is the best way to reduce the cost of car ownership. Consider how my lifetime vehicle expenses could pan out extrapolating from current data. I assume I'll drive 8,000 miles per year and that maintenance and car insurance expenses creep up over time:

Metric, Cumulative

Year 20

Year 15

Year 10

Current (Year 6)

Purchase price

$25,300

$25,300

$25,300

$25,300

Gas, maintenance, and other

$40,200

$30,150

$19,200

$10,800

Insurance premiums

$27,600

$20,400

$13,200

$8,800

Total expenses

$94,500

$75,850

$57,700

$44,800

Miles driven

170,600

130,600

90,600

60,565

Cost per mile

$0.55

$0.58

$0.64

$0.74

Cost per year

$4,725

$5,060

$5,770

$7,440

Data source: author.

Whether or not the estimates prove accurate -- or my car actually survives 170,000 miles and to 2033 -- can be debated. While there are diminishing returns from keeping an aging vehicle on the road, the numbers show I can squeeze considerably more value out of my vehicle.

You probably can, too. According to the U.S. Department of Energy, the average passenger vehicle and light-duty truck on the road was 11.6 years old in 2016. That all-time high is a testament to improving manufacturing quality and perhaps a little bit of a hangover from the Great Recession. Nonetheless, it shows that you can probably keep your vehicle well beyond the last payment, which is great news, considering keeping your car on the road for as long as possible is the single best way to reduce the cost of car ownership.