[mikestew]

why slushbox is bad for fuel efficiency

Automatics have been more efficient than manuals for decades. And the computer can shift a DCT faster than you can. These days a manual tranny is right up there with hand-crank starting your car: if you enjoy it, great, but don’t get smug because people don’t want to manually adjust the spark advance.

[qball]

>Automatics have been more efficient than manuals for decades.

No, they haven't. At least, not ones the average consumer could actually buy.

While it's true that modern 8 or 10 speed automatic transmissions do now compete favorably with 6 speed manuals, the former didn't meaningfully exist in passenger cars or trucks until around 2017. Neither did DCTs outside of high-end brands- sure, they're starting to do that now that "torque converter loss" means they don't pass emissions, but that was an option that commanded a premium back in the mid-00s when they were introduced (and still not actually more efficient than a manual outside of shift speed).

An automatic with 4 gears is less efficient than a manual with 5, much less 6 (this was the standard until about 2010 or so); one with 6 gears is likely on par with the 5-speed manual (and loses to a 6-speed, obviously).

So no, "decades" is bullshit. It's a very recent advancement.

[mikestew]

So no, "decades" is bullshit.

First car I looked up from 20 years ago (I own one), and the automatic does just a bit better than the manual:

https://www.fueleconomy.gov/feg/bymodel/2005_Scion_xB.shtml

We bought manual version despite that. You shouldn’t have a hard time finding other examples.

[bluGill]

Only because they cheap out and don't put in manual with optimal gear ratios. Otherwise the manual is better because you can use high throttle with low rpms - try that in an auto and you get high rpms which is bad for efficiency - but great for acceleration.