It's been another two and a half years since I posted about my hybrid car - how has it been doing now that it's getting past 100,000 miles and the original warranty period is coming to an end real soon (8 years on the electrical system)? Here's the same graph extended to another 30,000 miles of driving:
Once again the dark blue line is the main interesting one - the miles per gallon number averaged over 3 fills (the light green is for a single fill and much more variable). The seasonal variations and gradual downward trend I noticed before have both continued - but 2011 was particularly anomalous with no 3-fill average ever getting above 45 mpg, while in previous years the summer-time average had gotten close to or even over 50 at times. There was a definite change in my driving pattern starting in mid-2011, with fewer long drives and more shorter ones (about the same total mileage) - this may have had something to do with it. But things improved somewhat in 2012 without any further change in my driving - here are my yearly average mileage numbers since 2007:
That's almost a 10% difference between the best year (2007) and worst (2011). There are a few possible reasons for the changes in 2011/2012. I got all-new tires at 75,000 miles (October 2010) - and the new ones were standard Goodyear all-season radials, not the low-rolling-resistance tires I believe I'd had up to then - that could cut a couple of mpg and explain the 2010-2011 change. My oldest son started learning to drive in 2011 and got his license in 2012 - but he really hasn't put many miles on the car so I think it's unlikely more than a tiny fraction of the changes have anything to do with him. At 90,000 miles (December 2011) in a routine service I had all the spark plugs replaced - that should have contributed to the improved efficiency for the following year.
In general the car seems to be holding up just fine. I've had no repair costs associated with anything unexpected wearing out, just routine maintenance. It's not quite the stellar performer it was when I bought it 8 years ago - and there are certainly better cars on the market now. Yes, I dream of a Tesla Model S. But given my Prius' age I'd say it's doing just fine.