Small car/engine vs larger car/engine- fuel consumption

axer

Hi,

Does anyone know would a smaller car & engine consume more petrol than a larger/car engine at 130kph?

From my understanding the smaller/car engine will have higher revs than the larger car (think honda accord/avensis etc - say 1.6l) in at higher speeds but does that mean higher consumption or would it have less consumption due to the smaller engine cc?

Thanks.

Anan1

In my experience, all other things being equal, the larger-engined car will consume more. That said, you'll resent the consumption more in a car that struggles to accelerate.

R.O.R

I used to drive from Drogheda to Sandyford everyday for work. Most of the time I'd be in my 1.8T Octavia vRS, but sometimes I'd take the Wife's Ibiza 1.2.

It's Motorway practically all the way and traffic was similar on all the days, so it's a fairly fair comparison. I'd get around 35mpg in the Octavia and 32mpg in the Ibiza - both from the on board computer, but as it's the same unit in both cars they should be equally as accurate / inaccurate.

ShadowHearth

Well the way i see it:

The smaller engine you got, the heavier your foot has to be. So that means your MPG would be around same as driving bigger engine, and not pushing it to the floor.

A big big difference comes it on turbo engines. Specially on petrol ones.

EPM

Depends on gearing a lot. But as an example - drove to Dublin at weekend, cruise set at 140kph, bit of driving about Dublin and back to Cork. Piddly 1.6 Leon reving its guts out at 4.5k rpm all the way and got 28.5 mpg out of the tank.

Father has a 2 litre and did same trip recently - 38 mpg. Can't remember the exact rev's but it was a lot lower...

zilog_jones

R.O.R wrote: »

I used to drive from Drogheda to Sandyford everyday for work. Most of the time I'd be in my 1.8T Octavia vRS, but sometimes I'd take the Wife's Ibiza 1.2.

It's Motorway practically all the way and traffic was similar on all the days, so it's a fairly fair comparison. I'd get around 35mpg in the Octavia and 32mpg in the Ibiza - both from the on board computer, but as it's the same unit in both cars they should be equally as accurate / inaccurate.

As shown here, the engine has to deliver suitable power for the car, considering weight and aerodynamics. At that speed there'll be a lot of drag, and (correct me if I'm wrong) cars with relatively flat hatchbacks like the Ibiza are less aerodynamic than a "liftback" like an Octavia so will never be particularly great at motorway speeds. The 1.2 is the entry-level engine in the Ibiza so does not deliver much power (60-70 bhp depeding on which one) - fine for driving around town but not very well suited to motorway speeds. The 1.8T in the Octavia is plenty for that car though, so is not under very high load at high speed.

A more relative comparison would be a 1.2 Ibiza compared to a normal 1.6 Octavia, or maybe a 1.8T Ibiza Cupra compared to the vRS.

Matt Simis

Note the OP specifically said Small Car with Small engine vs Big Car with Big Engine. If we assume the Small car is light and the Big car heavy, then you have a scenario where the right engine is in the right car. You would be very hard pressed to find a well designed modern small/light car with a small engine being outdone by bigger car with a bigger engine.

The situation where you have small engines in large cars (BMW 518, 316, Superb 1.4) etc) is different as you have illogical engines in cars purely for legacy tax reasons, in those cases a larger engine may indeed be more economical.

zilog_jones

Matt Simis wrote: »

The situation where you have small engines in large cars (BMW 518, 316, Superb 1.4) etc) is different as you have illogical engines in cars purely for legacy tax reasons, in those cases a larger engine may indeed be more economical.

I'd say the same could be true for smaller cars when talking about motorway speeds, e.g. a 1.4 Golf, Focus, etc. versus a 1.6, especially if you're sticking to around 120-130 and overtaking a lot. I don't think 70-80 bhp is enough for most modern small cars, same for 60 bhp superminis. Maybe if you drive really economically you can get decent fuel economy with the least powerful engines, but that would probably mean driving 100 km/h instead of 120+ among other things...