Well, I finally ran through a tank of gas. This is my first full-emtpy-full, so I was able to calculate some results...
5.1 L/100 km over 734 km (456 miles)
That's 46 MPG US.
HOLY CRUD THAT'S BAD.
How bad? 46 mpg US combined is the
2004 Prius EPA rating (48 city / 45 highway).
I never
just get the EPA rating in any car. Something's wrong. If the calculated MPG is right, that's the worst fill-up (vs. EPA) I've gotten in years and years. Super-ironic considering the vehicle in question!
The car's fuel economy computer told me the tank was at 4.4 L/100 km / 54 MPG US; the un-calibrated ScanGauge II said 4.5 / 52 MPG. I thought those numbers were reasonable for the kind of driving I'd been doing (about 20% city short trips, 80% relaxed rural highway driving where I'd see trip numbers in the high 50's to low 60's).
I've read that the flexible bladder in the fuel tank can cause inconsistency in fill-ups (in terms of volume, that is: sometimes less, sometimes more fuel goes in depending on temperature and ???).
Hopefully that's what I'm seeing here. We'll know more at the next fill-up... and the one after that, averaging things out.
I don't think anything's wrong with the car itself. It runs well, seems to roll OK, glides very nicely. There's a big exhaust leak (muffler broke off), but I wouldn't think it'd cause a massive MPG loss.
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No recent mods to report
Maybe that's the problem!
I haven't done anything to the car since the kill switch & coro wheel discs. This fall I've used up all my tinkering time on a big project at the mansion. But I'm nearly done, so plan to spend serious time modding the Limo starting in January.