If you dunno about the formulas, better to get a friend to
calculate properly for you because its a very subjective
thing.
Generally, if you drive the full 10 years, your initial calculation
of depreciation before buying the car will be maintained.
For e.g. Car priced at $70k. Car PARF is $15k. So 70-15 = $55k
divide by the 10 years u drove it = $5.5k depreciation a
year.
So if you drive the car all the way till scrap, you would have
spent $70k on it (excluding rd tax, insurance, maintenance, loan
interest etc...).
If you sell halfway, you will most prob get a low selling price,
which means the 5 yrs u drove it becomes more 'expensive' in terms
of depreciation.
As above, driving it 10 yrs means u spend $5.5k a year on ur
car.
If let's say you wanna sell it after 5 yrs, and estimate it sold
for $35k, means you spent $35k on ur car to drive it for the 1st 5
yrs = $35/5 = $7k a year depreciation.
Other things to consider is like to keep the car for 10 yrs, mebe
the engine or gearbox will start having problems after a few yaers
so maintenance will go up. (Depending on make and model)
So gotta do maths first, can't juz generalise.
If the car is rare and can sell high price, then its diff.
For e.g, Skyline GTR R34, $256k when first launched. One owner
drove for 1-2 yrs, and still sell for $256k! (of coz prob got a lot
of high-end mod parts put in also)