Mazda 3 Forums UK

Technical Section => Maintenance => Topic started by: Hero_uk1 on July 27, 2018, 08:37:49 AM

Title: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on July 27, 2018, 08:37:49 AM
Hi Guys

My cars giving me low mpg (39MPG) when driving round town, is this normal? On autotrader its showing as 53.3 mpg (urban), i know autotrader isn't very accurate but my figures are way off.

My cars had full service history, had oil, filter and air filter replaced 2 weeks ago but still still get low mpg.

Have checked caliper to see if they are sticking but they aren't.   Checked tyres for pressure and they seem fine (32psi all round).

What MPG are others getting in 2nd Gen mazda 3 1.6 Diesel?

Please help!
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Ian345 on July 27, 2018, 09:42:44 AM
My Gen 2 1.6D (don't have any more) gave slightly better results - just over 40mpg around town and up to about 50mpg on a run.

Less than 40mpg around town in these high temperatures does seem a little low, but depends on your driving style and the traffic conditions.

Most cars will give no-where near the advertised mpg. HonestJohn truempg is a good place to look for some real data.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on July 27, 2018, 10:06:02 AM
Thanks for the reply Ian. I would say im not an aggressive driver and change gears when it displays on my screen.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: red_imps_2003 on July 29, 2018, 10:09:08 AM
I'm afraid I don't know what my typical mpg is in my 2nd gen 1.6d, as my daily commute is two thirds motorway and we tend to use my wife's smaller (petrol) for weekend runarounds. 39mpg doesn't sound too far off what it 'should' be, though, from my more casual observations.

How are you determining that figure, incidentally? Are you going off the on board display or using the brim-to-brim method? The latter is generally more accurate. Also, over what period of time? Have you just been measuring ad hoc journeys or was it over a more extended period of time? I would venture that urban journeys are more prone to fluctuations in mpg than regular stints on the motorway. As well as the tyre pressures already mentioned and the things you have already ruled out, how much weight you are carrying in your car (including passengers) can make a difference.

For what it's worth, my car typically averages mid-to-high fifties at the moment but, as I say, that is predominantly motorway miles and I drive very much with economy in mind over performance. The figure drops substantially during holidays when I do more driving around town.

If you are doing mainly urban miles, as it sounds, then you will need to be mindful of your DPF. It may not be getting much opportunity to regenerate (burning off the accumulated particles it has trapped) and risks becoming blocked. It may be worth sticking the odd bottle of Wynns or Millers DPF cleaner in and taking it for the odd 20-mile round trip on the motorway if that is not part of your regular routine. I also put a dose of Millers Diesel Power EcoMax (about £15 in Halfords or from Amazon) in the tank every couple of refills, which 'feels' as though it makes things run more smoothly.

It could be worth investing in a cheapy OBDII reader and downloading one of the many free sensor/fault code apps to see if anything pops up to give you further clues. I bought the one at https://www.amazon.co.uk/gp/product/B01N30RQNH/ref=oh_aui_bia_detailpage_o04_s00?ie=UTF8&psc=1 and the 'Torque Lite' app, which seem to do the job for less than a tenner.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Engineer Andy on July 29, 2018, 06:58:17 PM
Thanks for the reply Ian. I would say im not an aggressive driver and change gears when it displays on my screen.

You might find that the continuously very hot weather means that the mpg suffers because the A/C is not on 'eco' mode and is drawing more electrical energy and, as a consequence, fuel.  I just checked my mpg for my annual holiday down in the West Country and found that it was 'only' 39mpg, including two long runs of around 300 miles on the motorways, whereas when I've been (same place) in early-mid September, my car's averaged about 42-44mpg, so about a 10-15% reduction, probably because the external temperature was that much lower and the A/C didn't have to work so hard.  The traffic was about the same under both circumstances.  See what happens this week as temperatures are generally 5-7degC lower than the last week or so.

I would also check some of the go-to systems that can get clogged (DPF, CAT and EGR) - it may be worth buying some additives/cleaners, but also I would actually check to see IF the service work was actually done - another forum member reported (at my local dealer as well) that some of the consumables weren't replaced at the service despite being charged.  As you'll read on the forum, the quality of the service depts can vary considerably from dealer to dealer, compared to makes like Honda and Toyota.  Even more so an indies.

I suspect that you may find multiple causes, e.g. the A/C reducing it a bit and one or more of the other components mentioned needing a clean of some sorts, possibly coupled with a decent length drive and an Italian tune-up.  Bear in mind that a) 39mpg from urban only driving (even if using the brim-to-brim method) isn't that bad, especially if traffic levels are really high (I normally get 33-35mpg on that sort of journey with my 1.6 petrol) and b) the calculation method can make a decent amount of difference to the figure.  Trip computers aren't that accurate, though they are improving - nor can sat nav info be relied upon for mileage as it doesn't really know (and this take into account) differences in terrain (i.e. when you're going up and downhill), especially older systems.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on July 30, 2018, 02:49:51 PM
I'm afraid I don't know what my typical mpg is in my 2nd gen 1.6d, as my daily commute is two thirds motorway and we tend to use my wife's smaller (petrol) for weekend runarounds. 39mpg doesn't sound too far off what it 'should' be, though, from my more casual observations.

How are you determining that figure, incidentally? Are you going off the on board display or using the brim-to-brim method? The latter is generally more accurate. Also, over what period of time? Have you just been measuring ad hoc journeys or was it over a more extended period of time? I would venture that urban journeys are more prone to fluctuations in mpg than regular stints on the motorway. As well as the tyre pressures already mentioned and the things you have already ruled out, how much weight you are carrying in your car (including passengers) can make a difference.

For what it's worth, my car typically averages mid-to-high fifties at the moment but, as I say, that is predominantly motorway miles and I drive very much with economy in mind over performance. The figure drops substantially during holidays when I do more driving around town.

If you are doing mainly urban miles, as it sounds, then you will need to be mindful of your DPF. It may not be getting much opportunity to regenerate (burning off the accumulated particles it has trapped) and risks becoming blocked. It may be worth sticking the odd bottle of Wynns or Millers DPF cleaner in and taking it for the odd 20-mile round trip on the motorway if that is not part of your regular routine. I also put a dose of Millers Diesel Power EcoMax (about £15 in Halfords or from Amazon) in the tank every couple of refills, which 'feels' as though it makes things run more smoothly.

It could be worth investing in a cheapy OBDII reader and downloading one of the many free sensor/fault code apps to see if anything pops up to give you further clues. I bought the one at https://www.amazon.co.uk/gp/product/B01N30RQNH/ref=oh_aui_bia_detailpage_o04_s00?ie=UTF8&psc=1 and the 'Torque Lite' app, which seem to do the job for less than a tenner.


Hi

Im measuring brim to brim and using figures on weekly basis. i have connected obd2 device and does not come up with any error messages.

Thanks
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on August 28, 2018, 12:06:40 PM
Just changed Air filter to the pipercross, Miller's 5w30 Full synthetic oil with Bosch oil filter and now getting 41 MPG!!! EGR has had a blanking plate with a hole to stop EML coming on.

On the motorway im getting 44MPG for doing 100 miles at 60 to 70 MPH with Cruise control on. That can't be right!!!

Very poor MPG for a 1.6 Diesel, i was getting 60 MPG in my previous  car which was a civic. That's 60 MPG on the motorway.



Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: red_imps_2003 on August 28, 2018, 01:09:33 PM
It does sound abnormally low; especially your motorway figure. I've been averaging high fifties (brim to brim) over the summer with a mixture of mainly motorway commuting with a couple of miles of urban driving at either end. I also just got 62mpg out of mainly motorway driving from Devon to Newcastle with a full load and family on board. The lowest I've recorded in this car was around 45.2mpg, and that was in the depths of winter this year (with all that snow).

It's virtually impossible to figure out where the fault could lie. Could there be a leak? Is there a fault with the ECU or the MAF? Would a DPF close to blocking cause a drop in MPG? Away from hardware, the only thing I could suggest would be to run through a can of either BG244 or Archoil AR6400-D MAX (both of which seem to get decent reviews) for a tank followed by a shot of Millers Ecomax a tank or two later. Also, some people swear by services like Terraclean or Hydroflow (for about £100). The Terraclean did nothing for my own car but then there wasn't a particular 'fault' for it to work on. I must say I am sceptical about such products myself but, again, my powertrain seems to be in decent condition for the age of vehicle and I know it was well looked after from new by the previous owner. Some consumer reviews indicate improvements in mpg in using them but it is not always clear how they have arrived at those conclusions (I suspect many go off the numbers provided by the computer rather than brim to brim measurements over time).
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: amar1994 on August 28, 2018, 02:43:11 PM
Doesn't sound good  :( , I also get 35-40mpg in city , but 60+ on B roads and around 50-55mpg on motorway .
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on August 30, 2018, 08:17:42 AM
It does sound abnormally low; especially your motorway figure. I've been averaging high fifties (brim to brim) over the summer with a mixture of mainly motorway commuting with a couple of miles of urban driving at either end. I also just got 62mpg out of mainly motorway driving from Devon to Newcastle with a full load and family on board. The lowest I've recorded in this car was around 45.2mpg, and that was in the depths of winter this year (with all that snow).

It's virtually impossible to figure out where the fault could lie. Could there be a leak? Is there a fault with the ECU or the MAF? Would a DPF close to blocking cause a drop in MPG? Away from hardware, the only thing I could suggest would be to run through a can of either BG244 or Archoil AR6400-D MAX (both of which seem to get decent reviews) for a tank followed by a shot of Millers Ecomax a tank or two later. Also, some people swear by services like Terraclean or Hydroflow (for about £100). The Terraclean did nothing for my own car but then there wasn't a particular 'fault' for it to work on. I must say I am sceptical about such products myself but, again, my powertrain seems to be in decent condition for the age of vehicle and I know it was well looked after from new by the previous owner. Some consumer reviews indicate improvements in mpg in using them but it is not always clear how they have arrived at those conclusions (I suspect many go off the numbers provided by the computer rather than brim to brim measurements over time).


Ok so i have ordered Archoil AR6400-D MAX for my car and will post results.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: red_imps_2003 on August 30, 2018, 01:19:09 PM
Good luck! I hope it does something positive for you. I would be most interested to hear if it does. If it really does de-clog anything, you may well not notice until you run through the tank after the one in which you added it.

Incidentally, I have a bottle of the stuff in my garage, which I will try out at some point. I bought it with a refund I got on the BG244 I bought because they sent me the stuff for petrols instead, which I didn't notice until after I had tipped it it into my tank. Given that I have used the BG244 recently and have tried a number of other additives (Redex, Millers Ecomax, 2-stroke engine oil) over the past few months I think I will give it a rest for the next few months and try the Archoil early next year after a few months of additive-free motoring.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: audioslaven on August 30, 2018, 09:31:01 PM
are you down on power. The DPF could be full and leading to low miles but you would get an light or at least an silent error.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on September 03, 2018, 08:00:42 AM
are you down on power. The DPF could be full and leading to low miles but you would get an light or at least an silent error.

Power seems ok as i get nice pull. Don't think its DPF as no light coming on dash and been on motorway for about 150 miles to do  a italian Tune ::). MAF sensor has also been cleaned with Halfrauds Electrical Contact Cleaner.

Waiting for tank to go empty so i can put the magic stuff......
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: audioslaven on September 04, 2018, 10:20:24 PM
Did you scan the ECU for any silent errors as this could lead to an issue.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on September 05, 2018, 10:12:21 AM
Did you scan the ECU for any silent errors as this could lead to an issue.

I have used the Torque PRO app  and it did not find any errors
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on September 17, 2018, 11:03:57 AM
It does sound abnormally low; especially your motorway figure. I've been averaging high fifties (brim to brim) over the summer with a mixture of mainly motorway commuting with a couple of miles of urban driving at either end. I also just got 62mpg out of mainly motorway driving from Devon to Newcastle with a full load and family on board. The lowest I've recorded in this car was around 45.2mpg, and that was in the depths of winter this year (with all that snow).

It's virtually impossible to figure out where the fault could lie. Could there be a leak? Is there a fault with the ECU or the MAF? Would a DPF close to blocking cause a drop in MPG? Away from hardware, the only thing I could suggest would be to run through a can of either BG244 or Archoil AR6400-D MAX (both of which seem to get decent reviews) for a tank followed by a shot of Millers Ecomax a tank or two later. Also, some people swear by services like Terraclean or Hydroflow (for about £100). The Terraclean did nothing for my own car but then there wasn't a particular 'fault' for it to work on. I must say I am sceptical about such products myself but, again, my powertrain seems to be in decent condition for the age of vehicle and I know it was well looked after from new by the previous owner. Some consumer reviews indicate improvements in mpg in using them but it is not always clear how they have arrived at those conclusions (I suspect many go off the numbers provided by the computer rather than brim to brim measurements over time).


Ok so i have ordered Archoil AR6400-D MAX for my car and will post results.

OK the results are:

After putting Archoil AR6400-D MAX  i got 50mpg!!! round town :D

With just BP Diesel i get 42MPG!!!! round town

Does this mean my injectors or fuel filter need replacing because the Archoil AR6400-D MAX is manily to clean the fuel filter and injectors?



Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: red_imps_2003 on September 17, 2018, 12:41:01 PM
Wow! Those are really interesting results. If the previous low mpg has been prevalent over several tanks, as your other posts suggest, then it does look as though the fuel additive might actually have done something. Of course, the proof will be in whether this is now sustained over future refills. In theory, you shouldn't have to keep using the [hugely expensive] AR6400-D MAX in future tanks to sustain the improvements. My understanding is that this kind of thing is designed as a one-shot treatment (or, at least, to be used infrequently) to clean the fuel and filter systems out a bit by reducing buildup of carbon deposits rather than by improving the quality of the fuel itself. Archoil sell another product that, although expensive at the outset, is designed to be added a cap-full at a time to each tank and so last a lot longer. Or you could use the Millers equivalent (Diesel Power Ecomax). I currently stick a dose of the Milllers product in every second tank or so. Both supposedly replicate the additives contained in the premium diesels sold by the likes of Shell and BP but are cheaper by two or three quid a tank.

Please do let us know if this massive improvement in mpg is sustained. I'm naturally skeptical of fuel/oil additives but not to the point of being totally dismissive of evidence (however anecdotal) of potential efficacy. Like I say, I have tried out all sorts myself just to see what happens.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on September 24, 2018, 12:38:04 PM
Wow! Those are really interesting results. If the previous low mpg has been prevalent over several tanks, as your other posts suggest, then it does look as though the fuel additive might actually have done something. Of course, the proof will be in whether this is now sustained over future refills. In theory, you shouldn't have to keep using the [hugely expensive] AR6400-D MAX in future tanks to sustain the improvements. My understanding is that this kind of thing is designed as a one-shot treatment (or, at least, to be used infrequently) to clean the fuel and filter systems out a bit by reducing buildup of carbon deposits rather than by improving the quality of the fuel itself. Archoil sell another product that, although expensive at the outset, is designed to be added a cap-full at a time to each tank and so last a lot longer. Or you could use the Millers equivalent (Diesel Power Ecomax). I currently stick a dose of the Milllers product in every second tank or so. Both supposedly replicate the additives contained in the premium diesels sold by the likes of Shell and BP but are cheaper by two or three quid a tank.

Please do let us know if this massive improvement in mpg is sustained. I'm naturally skeptical of fuel/oil additives but not to the point of being totally dismissive of evidence (however anecdotal) of potential efficacy. Like I say, I have tried out all sorts myself just to see what happens.

OK another week has gone and im getting 41.8 MPG round town.

I have noticed abit of oil in cold side of the turbo (about table spoon), is this normal? I know turbos need to have little bit of oil to lubricate bearings etc but just wondering if that might be cause of low MPG.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: red_imps_2003 on September 24, 2018, 05:35:07 PM
Bummer that improvements were not sustained. I wonder why it shot up in that specific window?

A tablespoon of oil anywhere on the outside of components sounds a bit dodgy to me. I'm afraid I'm not mechanically minded enough to know whether leaks in the turbo area could translate into poor fuel economy though. Sorry.
Title: Re: Low MPG in 1.6 D 2nd Gen
Post by: Hero_uk1 on October 02, 2018, 12:43:57 PM
OK after another 321 miles of town driving i got 43MPG using BP Fuel. Looks like i'll have to  accept the fact im only going to get low 40 MPG round town in my mazda 3  :-\ :-\