Question about engine size and fuel economy

kissenger

kissenger

kissenger

Associate
Joined
10 Apr 2008
Posts
2,491
I recently bought a 1.6 litre '13 Skoda Octavia Estate that's supposed to get 80mpg 'extra urban' (whatever that means), but I'm finding I'm only getting around 55mpg on long commutes mostly driving at 70mph.

I was wondering if I'd actually be getting better fuel economy on those journeys if I had opted for the 2.0 litre version or is that not how it works?

In case you can't tell I don't know much about cars :confused:
 
Probably not is the short answer - but you'd also likely find both engines to perform to a similar level on that journey (from an mpg perspective)

The tests used to generate the figures are hugely unrealistic for most people's actual driving, hence the inflated numbers
 
All those mpg claims are fantasy don't worry about it. It would be very unusual for a larger displacement engine to have better economy, although the penalty is usually a lot smaller than people think.
 
While 'extra urban' sounds like it should mean a long motorway trip it really doesn't.

http://www.dft.gov.uk/vca/fcb/the-fuel-consumption-testing-scheme.asp

Also as the tests are done on a rolling road in a sealed environment with no wind resistance, steering movement and sometimes special oils in the engine to reduce friction it really doesn't represent anything like what you should expect in the real world.

As for 1.6 vs 2.0 in reality you can find the bigger engines to be just as fuel efficient in some conditions, sometimes the bigger engine will have taller gearing meaning its running a few less RPM for a given speed which can have a bigger effect on MPG than the slightly increased capacity.
 
kissenger said:
I recently bought a 1.6 litre '13 Skoda Octavia Estate that's supposed to get 80mpg 'extra urban' (whatever that means), but I'm finding I'm only getting around 55mpg on long commutes mostly driving at 70mph.

I was wondering if I'd actually be getting better fuel economy on those journeys if I had opted for the 2.0 litre version or is that not how it works?

In case you can't tell I don't know much about cars :confused:
Click to expand...

I managed 65mpg from a 1.6 TDI Octavia recently. Try harder :p
 
kissenger said:
I recently bought a 1.6 litre '13 Skoda Octavia Estate that's supposed to get 80mpg 'extra urban' (whatever that means), but I'm finding I'm only getting around 55mpg on long commutes mostly driving at 70mph.
Click to expand...
That's still better than some...
But as mentioned, the quoted values are the absolute best possible, under absolute ideal conditions (if not, outright fake) with nothing else switched on and all manner of cheats applied.

My 1.2L bike gets 50mpg on a long motorway run if I'm lucky, average 27 in town and 32 extra-urban.
However, a couple of fellow enthusiasts have tweaked theirs to achieve 70mpg, with another project underway to manage 80!
 
My rule of thumb is to look at the Urban figure, (ignore combined/extra-urban) and that will give you an idea of what you might expect on good day for an extended A-road / motorway run. Our car has never, ever hit the combined figure (never mind extra-urban) under any conditions, it is also a VAG 1.6 TDI and in over 3.5 years of ownership the all time best was 64mpg on the A3 in the summer last year I think. As winter is approaching you will probably get slightly lower mpg.

As for the question about whether the 2.0 might be better, officially it will probably have worse stats but for 70mph+ driving probably not a lot in it. If you reduce your speed to 55-60mph you should see better economy.
 
My quoted extra urban is 47.9 and the best I have achieved so far is 42 ish with a large portion of the journey 50 mph road works.

Your driving style will also affect it quite a bit.
 
The thing about the test numbers is just that, they're test numbers.

They're not real world numbers. For that look at fuelly and honestjohn as others have said.

What the numbers are meant for is comparing one car to another, since the test is (supposedly) controlled. (Exception: if a car is cheating...)

In other words if car A is advertised as 80 mpg and B as 60 mpg, then A will probably do better than B in real life (where they both get less than rated).
 
Last edited:
It depends on so many factors, one of the most influential being driving style that you really cant tell so easy.

My personal rule of thumb is the penalty in mpg for a bigger engine is in many cases outweighed by other benefits, like in those rare moments when you genuinely need your car to shift.

I used to regularly get ~65 mpg out of my mk1 fabia with the 1.9 tdi engine on a mountain road of all places.

Remember drag forces are proportional to speed squared, try dropping to 60mph instead of seventy and if you can handle the stone chips tuck in behind a lorry (you dont have to be audi close to get a benefit).

Also remember there's a surprising mpg difference between a "hard 60" and a "soft 60", what your trying to do is use the minimum possible amount of throttle to sustain your speed, most people tend to overdo it naturally.
 
The driver is by far the biggest factor,but, often a larger engine can - with restraint- prove to be more frugal.

I have a friend who operates a small fleet of trucks (bear with me!) and he's experimenting moving drivers from truck to truck to see who's the most efficient, he's found the younger drivers get far worse mpg no matter what they are in whereas the old boys are by far and away more efficient when using the most powerful and largest engined V8's which are both 16.4litre with outputs of 620 and 730bhp respectively,the reason being is they utilise the massive torque without ragging the nuts off it where the younger drivers seem to disregard this and enjoy the lovely V8 burble at higher revs and a considerable drop in mpg!

Top Gears feature where a V8 M3 proved much more efficient than a Prius in certain conditions is gained by the same principle.



 
Clarkey said:
All those mpg claims are fantasy don't worry about it. It would be very unusual for a larger displacement engine to have better economy, although the penalty is usually a lot smaller than people think.
Click to expand...

Indeed, in the same car, same weight it still takes the same amount of fuel/power to do the same amount of work. Usually the larger engine is slightly heavier and can be slightly less efficient hence the small difference.

Assuming that Octavia is the 1.6 TDI same as the Golf, I have managed over 75mpg so it can be done, but generally means sticking to around 50-55 not 70mph.
 
I'm fortunate I am able to drive to/from work at quiet times of the day (10am going and 8pm coming home).

I tend to sit at about 65 going to work (never in a hurry to get to work!) And am usually able to sit at 70-75 coming home for about 75% of the journey.

All in all I get the following MPG (Fiesta 1.0T) Official figures put it at 65+ MPG, which is insane.

24ndv0g.jpg
 
Getting good economy is a skill, and a very rewarding one, but you have you change your paradigm from one of "I need to get there in the shortest possible time" to "I want to drive as efficiently as possible".

The rewards can be significant fuel savings at a cost of usually no more than a few minutes on your journey.

Leave a bigger gap, coast as much as possible to minimise braking, try to avoid braking at all costs (if you brake when you could have coasted you were on the gas too long). Read the road ahead, anticipate 15 seconds ahead not 4 seconds...

Gentle acceleration, block changes, yada yada, you can easily turn a 55mpg car into a 75mpg car when you learn the behaviours.

I drive a 1.5 Mitsubishi colt and get 55mpg (Petrol) which I am pretty happy with.
 
You must log in or register to reply here.
Back
Top Bottom