Vehicle and travel

Fuel, charging, an instalment and a trip budget: the arithmetic a vehicle puts in front of you, run on prices and mileages you supply rather than on rates this page would have to keep re-dating.

Nothing on this desk is a price. Pump rates differ between cities and between stations in one city, and they are revised without notice; a public charger, a workplace socket and a home connection are three different tariffs; an interest rate is set by a lender for one customer at one time. Each of those numbers is an input here, because a page that filled them in for you would be publishing somebody else’s figure on somebody else’s day and calling it your cost.

What is fixed is the arithmetic, and it is printed on every page: distance divided by economy, multiplied by a price; a reducing-balance instalment; an annual cost divided by twelve before it is added to a monthly one; a value taken down by the same share of what is left each year. Where a calculation makes an assumption — that fuel is the only cost of a journey, that a depreciation rate stays constant, that a group splits a bill equally — the page says so next to the answer instead of leaving it buried in a formula.