New tyres.
 

I have just replaced my tyres with four all-weather tyres. Yokohama Bluearth 4S. These replace Yokohama Bluearth ES32's which were summer tyres (we don't get particularly cold weather and virtually no snow here. Plenty rain though).
The old tyres were rated C for economy whereas these are rated E. Already noticed a drop in mpg as shown on my ScanGauge. Could be as much as 10% but I will know once I get some top-ups recorded. I also notice a reduction in coasting ability. I do know that new tyres do kick the a$$ out of FE for the first full thousand miles. I believe the EPA does tests with tyres with 4,000 covered.

Thought someone as eco conscious as yourself might have chosen a higher rated tyre? Or was there a sale on? Haha. I'm running Yoko's at the minute on the GTi, not a bad tyre if I'm honest, although with my driving style, I couldn't tell you if they made a difference to fuel economy. Grip on the other hand...

After having Yokohama Bluearth for the past couple of years, I was happy to stick with them. And with the increasing amounts of rain we are having to live with and drive through, I decided to opt for the all-weather version of the tyres. Like you, I prefer grip over economy and the new tyres feel really grippy in the dry. I have yet to push them on wet roads.
I am not eco-conscious. I just like the "game" of trying for high mpg.

At 7500 miles a year or so I'll need new tires in about a decade. I'll be replacing them before that of course just due to age. My number one priority will be quietest riding.

75,000 miles from a set of tyres. That's good going. I had done 23,000 miles, and that was the front tyres down to 3 mm of tread. In the UK you are recommended to change tyres at 3 mm.
Checked my tyre pressures this morning and they were a few psig down from my normal higher than recommended pressures so my mpg may improve now they are back up.

Wellll, I probably exaggerated some on miles as even though the maker may optimistically tell you 75k with their warranty or whatever I doubt they'd go that far. They tell us we should change them at 4mm I think although they may have gone up to 6mm. I'll probably swap in 4-5 years at whatever that is, if I can wait that long to get the best rated quietest tires. I'll decide if I'm going to really splurge and buy lighter wheels. My wheels are really good looking though so maybe not.

Tyres is probably one of the biggest expenses running my car. Including the 4 the car had from the factory, I'm on my tenth tyre in less than 30k.

Not something I would want to boast about.

It's ok to keep the tires after the little nubs wear off. :)

I was stating facts not boasting. Its a big issue here with the kind of roads we have. Even maturer drivers find it hard to make a set last more than a year or so.