New car MPG

robfosters

robfosters

robfosters

Caporegime
Joined
1 Dec 2010
Posts
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Location
Welling, London
Do new cars require an MPG break in period so to speak?

It's just that my new astra is supposed to have an urban mpg of around 30, but I am currently only getting 20 from it.

Should it improve with time?
 
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Sorry, I am not car savvy enough to frequent this forum?

All I know is I drive normally and the mpg is only 20. I don't know what's going on. And how does sucking at maths come into exactly?
 
I assume you're working it out by putting fuel in the car, driving around and then putting fuel back in the car and working out how much was used?
 
If it is a brand new car then yes most cars have a breaking in period of about 3k miles to get to their peak performance.

P.s. What they say and what you get are 2 totally seperate things when it comes to mpg. Most of these figures are set on a rolling road with no air resistance and no weight in the car.
 
robfosters said:
Sorry, I am not car savvy enough to frequent this forum?
Click to expand...

Not at all, there are just some arrogant people in here that delight in being sarcastic, but in reality know very little.

robfosters said:
All I know is I drive normally and the mpg is only 20. I don't know what's going on. And how does sucking at maths come into exactly?
Click to expand...

The engine size and type (petrol or diesel) would be useful, and when you say "urban" driving are you literally spending all of your driving in heavy city traffic?

Also the way you measure the fuel consumption is important, on board computers can be very inaccurate and the only way to measure it accurately is to brim the tank, zero the trip meter and then brim the tank again when nearing empty. Then make a note of mileage and fuel used and work it out manually.
 
Your urban driving is almost certainly nothing like the urban cycle on the testing, so I wouldn't expect to match it, especially if the car has stop start tech and you aren't stopped for about 40% of your journey.
 
Engine/model is key info we need here
FYI the on board computer in my old astra vxr and current mx5 have both been spot on with me working it out manually. Mind you I never reset it.
 
Sorry for the delay. This is how Vauxhall list the engine and it's claimed MPG's. Also, my driving is more suburban than city traffic.

1.6i 16v VVT (115PS) (Automatic6), Automatic 6-speed

Fuel consumption, extra-urban driving mpg (litres/100km) 51.4 (5.5) 61.4 (4.6)
Fuel consumption, urban driving mpg (litres/100km) 28.5 (9.9) 39.8 (7.1)
Fuel consumption, combined mpg (litres/100km) 39.8 (7.1) 51.4 (5.5)
CO2 emissions (g/km) 167 129
Emission Standard Euro 5
 
You need to bear in mind that the claimed fuel economy from car manufacturers should only really be used as a guideline these days as the test cycles they do are not representative of real world driving.

What sort of average speed are you doing? How long are your trips and does the engine ever get warm? It doesn't help that you have an automatic either really. I would expect your economy to improve a little after a few hundred miles of driving.

Most new cars are typically something around 25% (or around there or there abouts) out in terms of fuel economy. So it sounds about right.
 
Same boat......my new 63 plate states that 83MPG was achievable, however I get 65. Still not bad though, better than the 36 I used to get from my old car

enjoy it.....
 
rims and tyres

i had a corsa 1.2 petrol with 17'' alloys and i think 225 tyres. It was a hire car with 4000 miles on the clock.

It was slow, boring and dull - most amusing though was the fuel - about 30mpg in the brief time i had it!!!!
 
As said above you need about 3k miles and even then it should keep improving slowly up to around 10k.

The 1.6 auto will need to be worked hard to get anywhere, which can kill the fuel economy.
 
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