About
How this site works
Plain-language guides on what owning a car costs: repairs, maintenance intervals, warranties, and the arithmetic behind keeping a car or replacing it. This page exists so you can judge whether to trust what you read here.
Who writes it
One person. Adrián González Chico writes and edits everything here, and that page sets out what he is and is not qualified to tell you.
What we publish
Miles & Keys is for people who own a car they did not buy new, who are deciding whether the next repair is worth it, or who want to know what the next five years of a car will cost before they sign anything. Every article tries to answer one question well rather than every adjacent question badly.
How we handle numbers
Repair prices, fuel prices and insurance vary enormously by state, by shop and by model, so a single national figure would be wrong for most readers. Instead we explain how a cost is structured and what the official sources say, and we show the arithmetic so you can put your own numbers in. When we do use figures, we say where they came from and when we last checked them.
Sources and verification
We start with government agencies, public universities, official standards and primary product documentation. Manufacturer sources explain their own products and are identified as such. We distinguish sourced facts from example calculations, state assumptions, and check important numbers against the original source. Prices vary by place and date; an example is not a quote. An editor’s source review is not an independent clinical or engineering review.
Corrections
Pages carry an updated date when the content has materially changed. If something here is wrong, send the URL, disputed passage and supporting source to our editorial email. We check the evidence, correct confirmed errors and show a material update date.
Email the editor about a correction.
Advertising
This site is funded by display advertising. Advertisers have no input into what we cover or what we conclude. There are no sponsored articles or affiliate links.
Safety
Some of the jobs described here involve jacking a car, hot exhaust parts, fuel and high-voltage battery packs. If a job calls for supporting the car, use jack stands on level ground and never work under a car held only by a jack. Anything involving airbags, brakes you cannot test, or the orange high-voltage cabling of a hybrid or electric car belongs with a qualified shop.