Fuel consumption

[Willpower]

There's only 1 real way to track MPG; firstly forget all the marketing blurb - test conditions cannot be replicated in the real world = seats removed etc..
I've got a CX5 on order and plan to monitor MPG using a tried and tested spreadsheet; I just enter the mileage from the oddometer, fill the tank (does not have to be empty, as long as you fill to max each time), then enter litres and convert to gallons.
I've been using this on several vehicles and is MUCH more reliable than any of the on-board trip computers!

If anybody is really serious about logging their fuel consumption, this is the only foolproof and reliable way of doing it.   Said it before, said it again.   It's not rocket science.

[Deeps]

I enter all fuel ups and services etc using a Smartphone App called 'Fuel Buddy' https://play.google.com/store/apps/details?id=mrigapps.andriod.fuelcons&hl=en . There's a short video on the same page demonstrating what can be done with this App.

On my PC I use Spritmonitor which is a German thing but also available in English. http://www.spritmonitor.de/en/ . They too provide an App (link on the page) which is also very good but I've gotten used to Fuel Buddy now so will remain with it.

[xtrailman]

I always use to log every tank full before average read out became common, but once I know an approximate error I will only use the average read out.  Except for rare occasions.

I'm not that concerned with the fuel economy and prefer to run will half a tank or less for my usual short trips, I only ever fill it up for a long trip and when towing. Lighter loads aid handling and improve economy so why fill up if you don't need too ?

[Dave]

I always use to log every tank full before average read out became common, but once I know an approximate error I will only use the average read out.  Except for rare occasions.

I'm not that concerned with the fuel economy and prefer to run will half a tank or less for my usual short trips, I only ever fill it up for a long trip and when towing. Lighter loads aid handling and improve economy so why fill up if you don't need too ?

Exactly my thoughts, like you I normally drive with no more than half a tank full unless on long trips.

However I decided to check the accuracy of the readout with a tank check, and as suggested the figures don't add up. I got a reading of 62.9 MPG as the average over a week's driving - 470 miles, and needed 37.06 litres ( 8.152 gallons) to top up again, using the same pump at my local station, giving me 57.76 MPG.



Here's the screen for my run back from work last night



And here's a screen shot of my run along the motorway:

[xtrailman]

I can only dream of returning those figures.

I'm going to fill to the brim today as promised, having done no motorway, but not trying to be economical, i do use full throttle on a few occasions over a trip.

I'm only showing a disappointing average of 39mpg, so i expect to see less with a brim to brim, i'm hoping to see a reduced error having done little high top speed driving. The manual car i had was around 41-43mpg on the average but i never bothered with a brim to brim with the car.

After that the next time i fill up will be next month when i tow.

[Dave]

I checked the ' real time' consumption figures occasionally (without trying to get too distracted!). Around town at 30MPH in 4th I'd get around 60 MPG but that would fall to around half when accelerating up to speed.

Motorway driving I'd get around 70 MPG on the flat but that changes dramatically even on seemingly slight inclines. I drive around the North west ( Merseyside and Cheshire) on my commute,  and the M57 / M62 is predominantly  flat but with some variation along the way.

Here's another screenshot down the M62 towards warrington at steady 60 in 6th down the incline - you can see the trip reading ~ 460 miles from my fill up, still a lot left in the tank.



Consumption is steady at around 55-60 but nudge over 65 MPH and the economy falls away.  I must clean the car soon too!

Economy figures this morning:

[Deeps]

I must clean the car soon too!

There's your problem then - aerodynamics. 

[BigAl]

I'm sure that aerodynamics has a lot to do with it. But (as I've said before), I cant help feeling that there's something in the software which increases fuel usage deliberately above 70 as if to penalise you for going above the national limit. Driving at a steady 70 by the clock is fine, set it to 70 via a sat-nav (indicates 72-73), the fuel consumption falls off a cliff! Its not exponential as you would expect from aerodynamic forces alone.

Alan

[xtrailman]

The max torque for the 175 is at 2000 rpm, so stick to that and i believe you will see your best mpg at higher speeds?
The 150ps has a max torque from 1800 up to around 2600, not sure about that last figure, but you get the idea it has a flat torque curve.

It appears there is a large consumption penalty for the extra 25ps.
Torque upto 1500 rpm is exactly the same for both engines, after that the 175 leaves the 150 behind.

Filled up again today brim to brim.
Average was 38.9 mpg, actual 36.52 mpg, so around 2.4 gal optimistic.
My last test was speeds up to 80 mph with an error of around 2.5 mpg.

So solo all i'll do is subtract 2.5 mpg of the average reading.

[Dave]

The max torque for the 175 is at 2000 rpm, so stick to that and i believe you will see your best mpg at higher speeds?
The 150ps has a max torque from 1800 up to around 2600, not sure about that last figure, but you get the idea it has a flat torque curve.

It appears there is a large consumption penalty for the extra 25ps.
Torque upto 1500 rpm is exactly the same for both engines, after that the 175 leaves the 150 behind.

I fully agree with your suspicions.  Both my 150ps CX5's are /  were very unforgiving at low revs. The diesel Seat Alhambra's I'd had previously could chug along in high gears at low speeds and be virtually impossible to stall, but once the revs drop in gear on the CX's they almost 'kangaroo' and jerk. 

I sold my caravan a couple of years ago so have never towed using my CX's but I suspect they wouldn't tow well, especially from a standing start. But for my purposes now they are fabulous, if they just tweaked the satnav and infotainment they'd be perfect.

[xtrailman]

I've never towed with the 150ps, but the 175 is a stonking tow car, the manual car i had would tow 1565 kg as low as 1250 rpm, but was happier at 1500rpm.
Solo i had it down below 1250 at times on the flat.
I noticed with the manual car that the change gear indicator would ask for a higher gear well below 2K usually around 1700 rpm.

The auto is completely different it often goes to 2K or above revs between changes, something the manual never asked for, which is why i believe it uses more fuel, along the the auto box losses.

I assumed the 150 ps with the same torque upto 1500 rpm would also be an excellent towcar.

[Anchorman]

I'm new to the forum and have read this thread with interest. I'm currently in a CX-3 with the 1.5 diesel, AWD and auto.  I have quite a demanding drive to and from work which goes over the hills from the Peak District to Manchester - 23 miles each way and I get about 42. The trouble is, this car is proving too small so I'm contemplating a CX-5 AWD diesel 175 auto.

If I could get approaching 40, I'd find that very acceptable given my current average (the published combined is 54!).  What I also enjoyed when I had a test drive was the excellent pulling power and the grown up suspension. I have had a succession of RAV4s and going to the CX-3 was probably what I expected but that car has Mazda 2 running gear and it shows. The suspension is way too soft for my liking.

[xtrailman]

Honest john apperas to give mpg figures around what i had and get, and what car also gives one model with which you can adjust driving style etc, both are worth checking out.

[Anchorman]

Honest john apperas to give mpg figures around what i had and get, and what car also gives one model with which you can adjust driving style etc, both are worth checking out.

Any regrets with your CX-5?  That's the one I would get.

[xtrailman]

No regrets its a good car, only the entertainment and nav bugs are the main issues, having said that Mazda cars do appear to have more problems that other jap cars i've had.