3 Cylinder Cars - Real World Fuel Consumption

[cr45]

I have always been interested in smaller cars with 3 cylinder engines for their good fuel economy potential. In order to get a feel for which 3 cylinder engined cars actually deliver on their promise, I have searched through the http://www.spritmonitor.de/en database for all the 0.9 to 1.0 lit cars - both na and turbo charged non hybrid - real world average fuel economys as recorded by their owners. Only cars with the ability to carry 4 or more adults have been selected.




The fuel economy average varies from 4.94 l/100 km for the Mitsubishi Mirage/Spacestar to 6.86 l/100 km for the Ford Focus 1.0 Ecoboost, a spread of 39 %. The graph shown below shows quite clearly that for a 3 cylinder car with an engine size between 0.9 and 1.0 litres that car mass significantly influences fuel consumption.



The plot also shows the line of best fit for this data along with the equation. The trend line would appear to indicate that a mass reduction will reduce fuel consumption even for the lightest cars, which are approx 840 kG.

Amongst this data are 2 Skoda cars that share the same 1.0 litre na engine. The Fabia weights in at 980 kG compared to 860 kG for the Citigo. If it is assumed that the average mass for the driver and fuel is 80 kG then the all up mass for the Fabia is 1060 kG and 940 kG for the Citigo. Hence the all up mass for the fabia is some 12.8 % greater than that for the Citigo. However, the Fabia actually burns 17.4 % more fuel than the Citigo, considerably more than what common wisdom would suggest. This almost certainly suggests that a 1.0 litre engine is just too small for a 980 kG car in the real world.

[cr45]

I have added the claimed NEDC combined fuel economy for some of the cars from the previous post. The last column shows the difference between the real world average compared to the official claimed fuel consumption as a percentage.

The car with the least difference between actual and claimed is the Mitsubishi Mirage 1.0 with a difference of 17.6%. As the weight of the car increases this difference increases markedly. The 1st and 2nd heaviest cars - Ford Focus and Ford Fiesta - show the greatest difference, 45% for both cars.

Buyers, caveat emptor!

[Baltothewolf]

Why is the Honda insight not on there? It's like, the most fuel efficient 3 cylinder on the planet...

[cr45]

Originally Posted by Baltothewolf

Why is the Honda insight not on there? It's like, the most fuel efficient 3 cylinder on the planet...

I am only looking at non hybrid.

Also all these vehicles are available to buy as I have avoided cars that are no longer built.

[oldtamiyaphile]

It's a 2 cylinder, but Fiat's Twinair should be on that list.

I'd also like to see a percentage comparison to NEDC in that table.

Anecdotally, I've also found that my Twinair is much more sensitive to weight than you'd expect.

Nice work though

[MetroMPG]

Thanks for the info.

Also worth noting (for non-Eurpoeans) that the Mirage / Space Star is available with a 1.0L OR a 1.2L engine in Europe. That's not a typo. I wish the 1.0 were available here, but Mitsu would never live it down.

[cRiPpLe_rOoStEr]

Gearing and the engine tuning obviously also play an important role on that matter much like weight, and a slightly heavier car might eventually rely on a lower differential ratio to keep some agility at the expense of a higher cruising RPM and a lower top speed.

[Ecky]

Nice thing about the Insight is that you can disconnect the hybrid system and it runs fine as a conventional petrol car.

On long trips I can approach 2.3L/100km average on the highway.

Of course, good luck finding one in Europe.

[Baltothewolf]

Beat me to the punch, Ecky.

I ran gas only in my old beater insight for 15k miles, averaged around 60mpg. That's back when I used to actually drive for MPG, though. Now I get 60mpg with a good battery. Lol. But I do drive 10mph faster than I used to, and am a looooot more aggressive in town.

[MetroMPG]

Originally Posted by oldtamiyaphile

I'd also like to see a percentage comparison to NEDC in that table.

And sample size.

For comparison, on the Mirage forum, we've got 142 owners reporting 3569 fills over 1 million+ miles / 1.6m km.

When broken down by drivetrain type:

1.2L 5MT avg (69 cars) = 44.8 MPG (US) = 5.3 L/100 KM = 53.7 MPG (UK)
1.2L CVT avg (70 cars) = 41.2 MPG (US) = 5.7 L/100 km = 49.4 MPG (UK.)
1.0L 5MT avg (03 cars) = 45.1 MPG (US) = 5.2 L/100 KM = 54.2 MPG (UK)

Euro Mirages are doing better.

However, many of the Euro Mirages come with automatic engine stop/start, where the majority of cars in our (mostly North American) database don't.