User Error or User Interface Error?
Most of the vehicles I've driven, especially those I've driven for any length of time, have had manual transmissions. Occasionally I'd drive something with an automatic transmission and those vehicles had the standard straight-line PRNDL or straight-line PRNDL21 controls, whether on the floor or on the steering column. I had, until very recently, never driven an automatic that had the new style zig-zag control that looks like it's pretending to be a manual shifter, almost. I ran into the equivalent of changing from a 4-speed manual to a 5-speed manual, where one can mistakenly think that fourth gear is the last gear.
The RX-350 has an automatic transmission with a zig-zag control. I drove it back from Detroit to Fairmont. I drove it from Fairmont to Minneapolis. And I wondered why I wasn't getting as good mileage as jmaynard did despite that I do quick accelerations less and have a driving style that tends toward efficiency optimization.
Last night I found out what was going on. It was a rather long day for both myself and jmaynard but his day started a couple hours earlier than mine, so when we stopped for gas in St. Peter, MN we traded places so he could rest some and I'd drive home. This was the first time I'd driven the RX-350 without driving solo. Jay pointed out that I'd shifted the transmission not into [D]rive, but into [4]. The transmission is a 5-speed.
I'd been doing that automatically as it felt like an interlock feature to me. Having two settings in the same vertical position is something I'd never experienced before. Interlocks I had experienced before, and acted accordingly or so I thought.
The layout is something like this:
P
R
N
4-D
3
2-L
As every other automatic transmission control I'd ever used had only one setting for each of the vertical positions here, I (mis)interpreted 4-D and 2-L as each being one setting rather than two.
That the panel indicator said [4] and not [D] didn't trigger anything, other than me wondering a bit on the way back from Detroit as I recalled it was 5-speed. But I didn't wonder enough. In hindsight, it seems pretty obvious. But it's one of those things that's only obvious after it's been explained and experienced.
On the drive from Detroit and the drive to Minneapolis I got mileage in the (very) low 20s. On the drive home from St. Peter, things went better, since I finally allowed the 5th gear to be used. This trip did have the advantage of being on fairly low-traffic highways at night so I didn't have to brake or accelerate very quickly to deal with other folks on the road. I also had the good luck to not need to stop for any of the traffic lights on the way home. The result was that the statistics indicators said I'd gotten about 28 mpg on the trip. And that on Minnesota's 10% ethanol gasoline. I suspect I might have broken 30 mpg with real gasoline.