Question of the day: Does more power in a car mean less mileage

Lokesh Sehrawat ‘Goldy’: Is it true that more the power in car, less the average. For example, a 1.5L car will have more power than a 1L of the same brand but which one will have more mileage?

Does a powerful car engine mean less fuel efficiency? That was what Lokesh Shrawat ‘Goldy’ wanted to know. And it is a very useful question. Anupam Potdar, a CarToq member, who shares valuable feedback and advice frequently talked about the inter-play of factors. Pankaj brought up the weight vs power ratio, citing the Fiat/Punto example.

Anupam Potdar: As a general rule it is true, but lots of other factors are involved — from the tuning, to cam settings and valve settings … also the general health of the engine and how aggressively you drive.

Another factor is the weight of the car…. for example older-generation engines from Ford, basically the 1.6 in the Fiesta Classic and ones before, were fuel guzzlers.

But the latest VW 1.6 engine in Vento is much more fuel efficient even though it is more powerful. And the fiat 1.4 is less fuel efficient than either of the above 1.6 models.

Pankaj Purohit: It depends on the weight vs power ratio. If a car’s weight demands a more powerful engine but has a less powerful engine, than it won’t be fuel efficient.

For instance, Fiat Punto weighs more than Swift, so the same engine feels sluggish and less efficient in Punto and better in Swift.

Pankaj Purohit: I have also heard that some 1.6 POLO’s giving better fuel efficiency than 1.2 petrol POLOs

Paras Dhir: It also depends on the type of fuel used. Whether petrol, diesel or CNG etc

Anupam Potdar: Lokesh, I think you are confused because of the ARAI fuel efficiency figures. They are only half truths. The cars are tested in such favorable conditions where even a big V8 will give 20 kmpl.

So you have to take it with a pinch of salt. You can subtract about 4-5 kmpl from the figures to get an approximate max FE figure. In city driving, it will be even less.

Dws Auto: As Anupam said, fuel efficiency is governed by various factors including engine size, the load on the engine, the way the engine is built (for eg. aluminium alloy engines are better than cast iron engines, overhead camshafts are better than push rods).

Basic rule is, lesser the load or friction in the engine, the more fuel efficient it will be. That’s one of the reasons car makers nowadays are opting for electronic power steering (which runs off the battery power) rather than hydraulic power steering (which runs off engine power), to reduce the load on the engine and increase fuel efficiency.

As Pankaj said a Polo 1.6 does sometimes give better mileage than a Polo 1.2 in city conditions, because the 1.2 has to work harder to pull the Polo’s weight, requiring more gear changes, while the 1.6 can handle the same load in a higher gear, thereby getting better fuel efficiency.

What’s your take on it?