How often should the air filter be changed?

Every 20,000 miles or 2 years for most cars. More often (annually) for very dusty conditions or short-trip rural driving.

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

Should I tap or blow it out? — No. Compressed air damages the paper element and lets dust through. Just replace.

Are performance filters worth it? — Marginal gains and require regular oiling. Standard paper filters fit and forget — usually the better choice.

Bob's Mechanical Repairs — independent family-run garage in Birnam, Dunkeld, Perthshire. Call 01350 727 276 or email bob@bobsmechanicalrepairs.co.uk.