Micra automatic or manual: which should you get for best gas mileage/fuel economy?

[MetroMPG]

The Micra's fuel economy ratings for the manual vs. automatic transmissions are practically identical: 7.7 vs. 7.8 L/100 km ("combined" rating -- see full Micra mileage ratings).

With numbers that close, you would be forgiven for thinking it doesn't really matter which transmission you get if fuel economy is a priority. But you would be wrong.

Here's why the manual is the one to get if you're serious about saving fuel.

But first, a little screening process...


If you're a "typical" driver (turn the key, turn on tunes, go go go)

Then you should just get the automatic -- it'll probably be more efficient and safer.

It takes focus to drive a manual transmission well, and driving one efficiently takes even more focus. You have to actively participate in every trip.

I hear so many manual cars going down my street at the 50 km/h speed limit in 2nd gear. (Normal every day cars, not fancy sports cars whose drivers are keeping the revs high to serenade the neighbourhood.) Those are the types of drivers who would be better off with an automatic.


If you're motivated to hone your driving skill to save gas

Then driving a manual Micra will beat the automatic's fuel economy by a BIG margin. Why?

Because those automatic vs. manual mileage ratings don't tell the whole story.

The laboratory fuel economy test



Drivers perform government certified fuel economy testing on a laboratory dynamometer by accelerating, cruising and decelerating at precisely defined rates. They literally stare at a compter screen hanging in front of the windshield and follow a trace, trying not to "colour outside the lines". It's like a big video game. And if the driver deviates from the prescribed speed by more than 2 mph, it's game over -- the test is thrown out and re-started.

This is relatively easy with an automatic transmission: Put it in "D", watch the screen, and work the pedals. The transmission will always shift gears up and down at the same points throughout the test, based on its programming. In other words, over multiple tests, the car will always get the same result (or extremely close to it).

When testing a manual, though, the driver is instructed on the computer screen exacty when to upshift and downshift.

Why? Because the fuel economy test has to be repeatable; the test driver can't be left to make shift decisions on his/her own.

And the key issue is: the shift points that the driver is instructed to use are not particularly efficient. They're meant to replicate "typical" driving (by typical brain-dead drivers who drive down my street at 50 km/h in 2nd gear. OK, probably not that brain dead.)

That means several of the simplest fuel-saving techniques are not used during the test, e.g:

1) short-shifting (up-shifting at lower engine RPM when only light/moderate acceleration is needed);
2) shifting into the highest possible gear (without lugging) once at cruising speed (even at sub/urban cruising speeds)

The manual testing rules also specifically prohibit another technique that can save fuel in the real world:

3) coasting in neutral at certain times.

The end result of these test restrictions is that most manual transmission cars can get significanly better fuel economy in the hands of a motivated eco-driver than their official fuel economy ratings suggest.


How much better fuel economy with the manual?

Short answer: it depends. Depends on the car, the route & the driver. (In other words: your mileage may vary.)



But here's a bit of data.

Let's look at real world results for Versa sedans (which use the same 1.6L engine as the Micra) tracking mileage on Fuelly:

• 9% - on average, automatic drivers (14 of them) are beating the EPA "combined" rating by this amount
• 19% - manual drivers (6 of them) are beating the same rating by this amount

OK, so that's not exactly a scientific study. But it matches my own experience.

I used to be an instructor for a company that teaches defensive driving as well as eco-driving techniques. For fun, I still sometimes take friends & acquaintances out to coach them on how to drive more efficiently in a sub/urban setting.



We always beat the official fuel economy ratings by a good amount. But the manual transmission cars beat the ratings by a LOT more than the automatics. Of 10 eco-driving sessions in 10 different cars (half automatics, half manuals):

• 23% - on average, the automatic drivers beat their "city" fuel economy rating by this amount
• 44% - manual drivers beat their rating by this amount

Manual transmissions simply give the driver more options for saving fuel than automatics.

So, if you're motivated and skilled (or willing to develop your eco-driving skills), I'd definitely go with the manual.

See thread: Head to head: 2015 Micra manual vs. automatic MPG/fuel economy comparison

Also: 2015 Micra fuel economy/mileage test: ecodriving a 5-speed and automatic in Montreal

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More info:

• For a more in-depth look at fuel economy testing and manual transmissions, see: Shift points: EPA testing of manual transmissions (why beating MT ratings is easier)
• For a description of the eco-driving coaching sessions and their results, see: Have you ever given 1-on-1 ecodriving instruction? (Here's how I did it.)