As a rule of thumb, if you cover fewer than 12,000 miles a year, a petrol engine is best. Diesel cars cost more to buy than their petrol counterparts, and you’ll need to cover quite a lot of miles to make up the difference in fuel savings. Do bear in mind that the used-car market values some petrol-engined cars (particularly SUVs) less favourably than their diesel counterparts, as used buyers are often put off by the increased running costs of larger petrol engines. Conversely, most petrol-hybrid models offer lower running costs than their petrol-only counterparts.
