myfuel consumption seems very poor I think?

With exactly 48 litres of fuel I managed 650 kms. Thats about 38 miles to the gallon if I have calculated it correctly???
Seems very poor to me for a 2009 Mazda 5 diesel 2 litre....I would say 80% motorway driving. Its a new car for us so we might have not made full use of the 6th gear. (never had 6 gears before).
What should we be getting......?
Any tips......?

Hello there i drive a honda civic 4 door saloon 08 reg its a 1.8 i v-tec i currently get 50mpg and i also have six gears now when you get to 100kmh then you should by now be in sixth gear. Do you use cruise control and have you got a sunroof or do you leave the windows open alot ?

There is definitely something strange about this mileage. I have a BMW 2.0 Petrol and get 30 MPG around town. A friend is driving a 2.4 ltr Diesel Volvo and getting 58 MPG, mostly motorway. Fast acceleration burns a lot of fuel, could this be part of the problem? Is the car well serviced? Are tyre properly inflated to spec?

In this review [broken link removed]the reviewer averaged 36 mpg,so yours sounds about ballpark.

no sunroof....
windows are always down....
and vandriver.....that review is for the higher brake horse power model for combined driving. We have the lower brake horse power model and mostly motorway driving.
Is the maths correct from my original post???

Your maths is correct.Apparently,the two power levels have identical mpg figures.Also,is this your first diesel motor?I ask because high revs and high speeds are very costly on fuel consumption and diesel does require a more relaxed light footed driving style.
I read somewhere that the difference in consumption between 60 mph and 70 mph is 20%.
Is the 6th gear an overdrive?If so you should use this when cruising.

Does using cruise control increase fuel consumption? I use cruise regularly on any sort of long run.

lfcjfc said:

does using cruise control increase fuel consumption? I use cruise regularly on any sort of long run.

Click to expand...

yes !!

My (physics type) theory behind this is as follows.....
When you accelerate and decelerate an object above and below an "average speed", more work is done than if you had constantly maintained that average speed.
Cruise control makes hundreds of alterations of the throttle fuel flow every minute, thus hundreds of tiny accelerations and decelarations above and below an average speed.
The average driver rests his foot on the accelerator pedal and will not be aware of small changes of speed due to small road inclines and descents.
Also when the throttle is opened and the car accelerates (by the driver or the computer i.e. cruise control)..there will be a reletave increase in fuel consumption 1. Due to inertia (reluctance to move or accelerate) and 2. due inefficiencis in the increase in fuel burn required to accelerate the car.
So the most efficient way of driving a car is to keep your foot on the accelerator pedal in a fixed position. On level road say you are driving 100 km/h, as you go up and down hills, accept the speed changes, but do not move your accelerator foot position.

This is how I explain it......I am sure someone can explain it better than myself.....or tell me I am talking rubbish.

landlord said:

yes !!

My (physics type) theory behind this is as follows.....
When you accelerate and decelerate an object above and below an "average speed", more work is done than if you had constantly maintained that average speed.
Cruise control makes hundreds of alterations of the throttle fuel flow every minute, thus hundreds of tiny accelerations and decelarations above and below an average speed.
The average driver rests his foot on the accelerator pedal and will not be aware of small changes of speed due to small road inclines and descents.
Also when the throttle is opened and the car accelerates (by the driver or the computer i.e. cruise control)..there will be a reletave increase in fuel consumption 1. Due to inertia (reluctance to move or accelerate) and 2. due inefficiencis in the increase in fuel burn required to accelerate the car.
So the most efficient way of driving a car is to keep your foot on the accelerator pedal in a fixed position. On level road say you are driving 100 km/h, as you go up and down hills, accept the speed changes, but do not move your accelerator foot position.

This is how I explain it......I am sure someone can explain it better than myself.....or tell me I am talking rubbish.

Click to expand...

I follow exactly what you are saying, but I would suspect that the actions of most peoples right foot would be a lot more "heavy handed" in trying to maintain a constant speed that the very slight fluctuations by the on board computer.
I would suggest that most people trying to maintain, say, 100Kmh will quite often allow the speed to change by at least +/- 5Kmh before taking corrective action and thus heavier throttle usage will ensue.

Anyway, even on a clear level road, you are constantly adjusting your throttle trying to maintain a constant speed,(wind changes/unnoticed inclines etc.) even if you are not consciously doing it.

I found this on Wikepedia....

"Driving over "rolling" terrain, with gentle up and down portions, can usually be done more economically (using less fuel) by a skilled driver viewing the approaching terrain, by maintaining a relatively constant throttle position and allowing the vehicle to accelerate on the downgrades and decelerate on upgrades, while reducing power when cresting a rise and adding a bit before an upgrade is reached. Cruise control will tend to overthrottle on the upgrades and retard on the downgrades, wasting the energy storage capabilities available from the inertia of the vehicle"

SparkRite....."Anyway, even on a clear level road, you are constantly adjusting your throttle trying to maintain a constant speed,(wind changes/unnoticed inclines etc.) even if you are not consciously doing it."..............Agreed !!!! but i guess my point is the cruise control will be making many many more corrections to the throttle in that period. I would think, that alone would have more impact on the fuel economy than as you suggested .....the effect of a drivers larger throttle correction.

I am finding some reports on line saying the opposite of what I thought...... If you are a naturally aggressive driver accelerating and braking very hard and driving on motorways at high speed than it appears that cruise control could save you fuel.

Any experts out there shed some light on this........

It seems very great problem. the Mazda 2009 is also not to much economic car. if you are not doing proper service then you have to suffer from the millage problem. and also in the beginning the car take some time to come in its actual performance.[FONT=&quot]
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