Fuel economy tanked, things I can look into?

[hornblower]

Combination of shitty fuel economy from winter gas and required service.

[Pinchy]

I had the exact same thing happen, literally overnight.  One day I'm getting 12L/100km and the next I'm at 16L/100km.  The only thing that changed was the brand of fuel I bought.  I find that the ethanol blended crap has a huge impact on mileage, so if you can find a station without it you might do better too.  Some Shell stations have regular without ethanol, but it seems most places now the only way you get it without ethanol is to buy mid-grade or premium.  Good luck!