My sister’s 2005 Ford Focus 1.6 is getting very poor fuel economy, about 24mpg on short trips and about 29mpg on long trips. I have fitted new plugs, air filter, oil and oil filter. I’ve also checked the tyre pressure and tracking, but have not seen any improvement in mpg.

The car has 105,000 miles on it and has not been thrashed around like a boy racer car, but she does put about 200 motorway miles on the clock at about 60-70mph a couple of times every month.

If anyone could help me by giving advice on what to check before she takes it to a garage I would be very interested to read what the problem could be. I have been doing my own cars servicing for years and have some useful tools to hand, OBD 2 scan tool, vacuum gauge, compression gauge all the usual DIY tools.