So, I thought treat the engine to some nice oil, so put in Shell Helix long life last service time, correct viscosity etc.

MPG dropped but I assumed it was down to tyres as I changed them at the same time.

Lo and behold, car comes back from service with standard oil and my mpg improves again! Air filter was not changed, ditto fuel filter.

Anyone else experienced this?? Difference is average of 50mpg, was 46/47.

I did in my Mk1 Fabia VRS in a sightly different way. Went in for its service in main dealers came out and mpg was a good 10+mpg less.

that's odd!

that's odd!

Yea, I thought so too but no explanation it had full dealer service history and that was only its 30K service ffs! If anything I was expecting more as it was nicely run in. I was a master at eco driving in it. Really peeved me off for a while. Then I sold it and ordered the Octy..... But on the plus side in the Octy tonight on a cold engine all town driving max 30mph for some pizza without getting engine up to 90 Deg C I got 49.4MPG over 15 miles

Yes - I have to say I'm made up with the MPG on mine, did not expect it to be so good