My 1997 300Tdi Discovery ES auto (mileage 117,000) is returning only 20mpg whether off-road, on-road, round town or on the motorway. I’ve just given it a new air filter, oil and filter, fuel filter, gearbox oil, fuel treatment and oil additive. It’s a non-smoker, sounds okay and will do about 90mph without too much effort at 2800/3000rpm. Also, the cruise control has stopped working. Any ideas?
Matt Varney, Nottinghamshire
I assume you don’t spend most of your time at 90mph – if so, 20mpg is actually quite impressive! I’d expect a 300Tdi auto to get between 24 and 25mpg if driven sensibly, so you’re not far away from where you need to be.
Unfortunately, the most likely cause of the high fuel consumption is wear in the injection pump; and these are very expensive to recondition. I’ve known of people who see an increase of up to 10mpg when they’ve had reconditioned pumps fitted.
The most common cause for the cruise control not working is the vacuum pipes running to the actuator or the brake pedal switch. Check the vacuum hoses first, because they’re the most common fault and cheap to replace.