Q Does my diesel car need to be drivean hard occasionally?
My 10-year-old volkswagen Golf 1.9 TDI runs well but is used only for short local trips. Friends tell me it needs a 'good long run' now and again. Is this true?
**Cathy Walters, via e-mail
Driving a car hard for a long run is still worth doing now and again, especially for older diesels that get used only for local runs. The problem is that carbon can build up in engines that don't get 'opened up' or never reach their proper operating temperature, and that can affect their efficiency. Staying in a low gear and keeping the revs very high for a few minutes gets the engine up to a high enough temperature to burn off and shift carbon deposits. The engine must be warmed up first, and there's no need to drive at silly or illegal speeds. Doing this every month or so can keep your engine working efficiently.**