Thankfully the previous fill-up was indeed a victim of garage-time and the last one was back to a solid ~35 MPG (6.8 lhk). I'm about two-thirds into the next tank and I don't want to jinx it, but it may be the new personal best
Random observation: the car seems to roll noticeably better after switching back to summer tires (165/65R13 instead of 145/70R13) which leads to think that in this case it's not about the size but the tire design (tread, compound, construction?).
And finally I got a working temp indicator, although:
1) I had to pay for a new one, as the mechanic could not get the other one to work
2) Apparently, the adapters available on market were only for a certain hose diameter, which happens to be the one
after the thermostat in my car. This means I get readings only after the thermostat opens
Here is the new twin brother to the tachometer. Since it was still pretty cold when it was mounted, I did not want to try and attach it with the adhesive provided. Now it's warmer and it sits firmly on the dash.
Since the new indicator annoys me at night, giving a reflection on the windshield, and since I haven't given up on the idea of a kammback but still haven't decided on a good material, I decided to experiment with a DIY technique that I saw on this forum (cardboard, wood glue, cloth) and made two small shields that I will place on top of the indicators. If this proves sturdy enough (will mount them next weekend), I will probably give the kammy a second shot.