Why is the fuel economy so poor in my Vauxhall Insignia?

I recently purchased a 2009 Vauxhall Insignia 2.0 diesel with 140.000 miles on the clock. It has a full service history and drives well. However, the fuel economy isn't very good. I average 36mpg, yet the car should give at least 45mpg, Is this a sign that the car has an issue?

Asked on 23 September 2016 by Marian

Answered by Honest John
I tested this model some years ago and averaged 55mpg. But soon realised that a lot of this was down to the hard, low rolling resistance tyres. Probably 5mpg. Give it a proper check on Shell V-Power Nitro Plus over 200 miles or more. If you're still not getting 45 then something wrong. Probably worn injectors.
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