I have owned this car for five years and throughout this time have cared for it in every respect and it has never let me down.
As a means of checking performance I occasionally use a twenty mile identical journey as a test to ascertain MPG.
Ensuring that everything is the same on every trip (same speed, same gear, same load, correct tyre pressures, no gear changing, similar weather conditions etc), I set the trip computer to zero and with engine already warmed up, obtain the same very good MPG without fail….until now

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Last Thursday, the five-year service was carried out and on Saturday and Sunday I needed to make the same journey so, as usual, made the same MPG test. On both occasions the MPG was down by 10% !
I have not yet contacted the garage because they would probably point out that the ‘service’ was mainly an ‘inspect everything’ occasion which did not involve any engine adjustments and would then offer an ignition timing check at my expense.
Would anyone care to suggest why I should suddenly experience this disappointing change? I have deliberately not mentioned the actual MPG because most people would tell me how fortunate I am to achieve such good figures…with which I would agree but that is not the point of my thread.