How often should the fuel filter be changed?

Diesel: every 20,000–30,000 miles. Petrol: most modern petrols have a sealed lifetime filter inside the tank — only changed if a fault occurs.

Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.

Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email [email protected].