New car MPG

On brand new ex-factory cars, is there a period where the engine is so-called bedding in and the MPG will be lower than the average MPG expectation stated for the model? Or does this apply to cars of a previous era and that you get the MPG pretty much straight away that you will be getting throughout the life of the car (supposing it is well looked after and not caned).

Having looked on the trusty interwebs there doesn't seem to be a concrete answer to this, or not that I've found.

Can any of the GC auto afficionados clarify?

Cheers
GG

 

Hiya.
Back in 2003, I bought a new MX5. At first I was only getting around 180 miles from a tank. After a few months, this went up to 240 from a tank. So yes, I would guess it takes a bit of time for the engine to loosen up a bit. Btw, I wouldn't have too much faith in the official MPG figures.

 

"Running in, please pass"
45 mph for 500 miles.

 

Blimey Pete, that takes me back !

 

Same here , Running In , when did you last see that !
GG for some unknown reason , MPG figures on cars are calculated by computer program after a very short controlled test run . To achieve the published MPG would be amazing .

 

Have you got one of those displays that shows average MPG?
And also instant MPG.

Mine is very inlightening, it goes from around 7MPG, foot down going up hill to around 50mpg coasting downhill.
Just shows how you drive, and where, makes all the difference.

 

A while back I had a 5.3 litre Jaguar XJS. I lived 3.5 miles from work and in the winter it did 8.5 mpg to work and back and in the summer 12.5 mpg - because it was warmer. On a long run on the A1 I could get 40 mpg or more.

So as Pete says it all depends on the circumstances. The mpg displays are very interesting. I wish my Mondeo had one.

I understand the mpg tests have to abide by EU regulations but are entirely unrealistic as they can be manipulated. I have read that they are allowed to reduce the weight of the car by removing spare seats etc. They can remove the alternator and wing mirrors and are allowed to tape up all the door openings etc to reduce drag, and fit special tyres which are overinflated. http://www.dailymail.co.uk/news/art...fuel-economy-figures-new-cars-good-think.html

 

Thanks for replies.

@fat controller - I was wondering if the technology had changed so that is useful. I noticed with my old car that the MPG drastically improved after several weeks of driving, that was in ye olden days though. Early days with my new car but it seems to be getting very good milage straight out of the box. Only two tanks of petrol used so far but clocked via on board computer thingy and doing it brim to brim calculations and I'm being gentle with it a bit as per the running in manual instructions. I do 80% A road and 20% town so fuel economy tends to be good anyway even on the old Corsa.

@pete - yes, it has more gizmos that I know what to do with, I think 8 different sorts of milage related readouts. Gawd it's even got electrickery windows. Also has an Eco light that comes on when you are driving for optimal fuel economy which is pretty much common sense really. Can't tell you what the instant MPG reads other than in town vs A roads as it's flat as a pancake round here, biggest hills are the speed bumps in Sainsburys

GG

 

There is no need to "run in " a modern car engine. But as the miles go on the engine beds in so becomes just that bit looser. The frictional reductions allow the engine to spin freely and this reduces the amount of fuel to make it spin. MPG will go up once this has taken place. A diesel takes longer to do this and MPG will rise by as much as 5. It can take 15.000 miles or more before the engine reaches its optimum.

Ambient temperature is a separate entity but as others have said will have a large bearing on MPG ..

 

Used the wrong word @shiney , what I meant was going down hill in gear but no throttle or brake.
Not sure what the right term for that is?

I occasionally put it into neutral when coming to a stop at lights etc. but not for any length of time.

 

Going down hill in gear but no throttle or brake. That is called overrun Pete.

Things not to try , free-wheeling down hill and turning the ignition off - steering lock can come on ! Or free-wheeling downhill turn ignition off and you have no power steering - steering is unbelievably heavy !