Bad fuel efficiency 184ps?

Feb 23, 2021
9
3
Done a lot of research online before buying the car, 2016 version, a lot of people seem to be getting only 5 litre/100km or below, my dash is telling me long term 9 litre/per 100km I do a lot of town driving but still unsure how its so high? I don't hammer it around the place 24/7 and it still seems really high or am I just over thinking? Thanks in advance
 

SRGTD

Active Member
May 26, 2014
1,181
528
I think that 9 litre / 100 km is roughly 26 mpg, which does sound quite poor for a 2.0 diesel Leon. However, if you’re doing mainly town doing and (presumably) mainly short journeys, you‘re likely to be doing quite a lot of stop start driving in lower gears and your car’s engine probably won’t be getting a chance to warm up fully, all of which will have a negative impact on your fuel economy. Also, lots of town driving probably means the DPF frequency is quite high, which will also have an adverse impact on your fuel economy. There will also be other factors that influence fuel economy - e.g.
  • tyre pressures; if your tyres are under-inflated, this will have an adverse effect on fuel consumption.
  • ambient temperature; with the diesels I’ve owned, I found that the fuel consumption was always worse in the colder (winter) months than during the warmer months.
  • winter diesel; the change from summer to winter formulation for diesel fuel usually means fuel consumption suffers during the winter months.
  • If your car is fitted with roof bars or a roof box, or you regularly carry other items carried on the car’s roof (e.g. cycles) that would create drag and result in an increase in fuel consumption.
I see from your forum signature details that you are in Italy, so it might be that in the region of Italy you live you don’t get particularly cold weather during the winter months. Also, Italy may not switch over to winter diesel, so the points above regarding winter temperatures/ winter diesel may not be relevant to you.

If you’re not currently under lockdown conditions that restrict the use of your car, it would be worth taking your car on a few longer journeys of, say, 50-60 kms or longer to see how your fuel consumption compares to your current long term average.
 
Feb 23, 2021
9
3
I think that 9 litre / 100 km is roughly 26 mpg, which does sound quite poor for a 2.0 diesel Leon. However, if you’re doing mainly town doing and (presumably) mainly short journeys, you‘re likely to be doing quite a lot of stop start driving in lower gears and your car’s engine probably won’t be getting a chance to warm up fully, all of which will have a negative impact on your fuel economy. Also, lots of town driving probably means the DPF frequency is quite high, which will also have an adverse impact on your fuel economy. There will also be other factors that influence fuel economy - e.g.
  • tyre pressures; if your tyres are under-inflated, this will have an adverse effect on fuel consumption.
  • ambient temperature; with the diesels I’ve owned, I found that the fuel consumption was always worse in the colder (winter) months than during the warmer months.
  • winter diesel; the change from summer to winter formulation for diesel fuel usually means fuel consumption suffers during the winter months.
  • If your car is fitted with roof bars or a roof box, or you regularly carry other items carried on the car’s roof (e.g. cycles) that would create drag and result in an increase in fuel consumption.
I see from your forum signature details that you are in Italy, so it might be that in the region of Italy you live you don’t get particularly cold weather during the winter months. Also, Italy may not switch over to winter diesel, so the points above regarding winter temperatures/ winter diesel may not be relevant to you.

If you’re not currently under lockdown conditions that restrict the use of your car, it would be worth taking your car on a few longer journeys of, say, 50-60 kms or longer to see how your fuel consumption compares to your current long term average.
My short journeys are quite small but the oil temp always gets above 90 when driving. I am currently in Ireland 😂 Ye winter months here at the moment, between 0-15 Celsius so that could be the problem also. I'll check the tire pressure and bring it on a long drive up the motor way with some injector cleaner and see if it makes a difference. I was looking and people saying there getting at least 40 mpg even in towns so I was quite shocked to see my long term at 8-9litre/100km which is 25-30 MPG. Thanks for the response!
 

Mr Pig

Active Member
Jun 17, 2015
2,023
651
Our 150 DTi got 38mpg last tank and that is the lowest I've seen, It is typically around 50mpg and that is predominantly short trips. I know it's lockdown etc but 38mpg, damn.

25-30mpg? I'd say that's broken.
 
Feb 23, 2021
9
3
Our 150 DTi got 38mpg last tank and that is the lowest I've seen, It is typically around 50mpg and that is predominantly short trips. I know it's lockdown etc but 38mpg, damn.

25-30mpg? I'd say that's broken.
Any idea where to start to try and work out the issue? Straight to a garage for a service? I only purchased the car 2 weeks ago with 79000 km on the clock and full service history looks grand.
 

SRGTD

Active Member
May 26, 2014
1,181
528
If the car data in a Leon works the same as it does in a VW, it re-sets itself after 100 hours of driving time. So if your car’s data has recently reset itself and you’ve driven mainly short journeys, that could help explain your higher than expected fuel consumption. If the car hasn’t done a recent reset, then the long term fuel consumption figures will largely reflect the previous owner’s journey types and driving habits as you’ve only had the car for two weeks. Also bear in mind that the car’s fuel consumption figures might not be accurate.

In your position, before taking it to a dealer to investigate and they tell you there’s nothing wrong, I’d run a few brim to brim tankfuls of diesel and manually calculate your fuel consumption. Don’t assume that the figures displayed on your instrument panel are correct.
 
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Jay5959

Active Member
Apr 26, 2020
176
77
Those figures do seem high, I normally get between 35-40 mpg around town and 55+ on motorway and longer journeys in my 184, even with the car full (or at least that’s what the cars computer is telling me!)
 
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Mr Pig

Active Member
Jun 17, 2015
2,023
651
Any idea where to start to try and work out the issue?
First, I'd make sure you really have an issue. You need to work out your actual mpg. It's quite simple.

Fill the tank to the brim and reset the trip counter.

Use up most of the fuel and go to the garage to fill up.

When you fill up, make a note of the miles on the trip counter and fill to the brim again. Also make a note of he number of liters of fuel that went in. So you've got two numbers. The miles you've done and the number of liters you've used to do them.

Let's say you've done: 399.2 miles
and used: 46.2 liters

First thing to do is change the liters to gallons. Multiply the liters by .22

46.2 X 0.22 = 10.164 gallons

Then just divide the miles by the gallons

399.2 / 10.2 = 39.1 mpg

Once you know exactly what your mpg is you'll be better placed to think about what to do. If it is really low you'll also be able to tell the dealer you've checked it. Personally, I think you'll find your real mpg is better.

Won't hurt to check your tyre pressures and check for a binding brake. Look for a hot wheel after a drive.
 
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Feb 23, 2021
9
3
Recently filled the tank and drove about 50km since filling. Reset the long term consumption before driving today and went on a 60km ish motorway drive just to see, 50km was motorway rest city. average speed was 60kmph. (Was lashing with rain so wasn't a completely fluent drive!) It read 6l/100km after parking back up so could be just the short journey driving. Thanks in advance will keep an eye on it and do as you guys advised, just a bit scary to seeing others MPG and then mine only after buying the car!
 
Feb 23, 2021
9
3
It does seem excessive. I had a 184ps Leon in the past and averaged about 50mpg but there was a few long trips involved.

If your readings are accurate, your TDi is less efficient than a Cupra!

I hope there is some calculation error or hopefully a sensor issue that is giving false readings.

I'll be following this post as I'm thinking about a used Golf GTD for journeys when lockdown lifts.

All the best.

Sent from my moto g(7) power using Tapatalk
Cool! I will do the manual calculations and see how it turns out will update this post when I have done it.
 
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Feb 23, 2021
9
3
It's a pain in the rear to do manual calculation but hopefully it may give you insight on the true mpg.

I don't have many tips on how to do it apart from brimming the tank and man maths!

I know my old FR184 would happily return upto 55+mpg on long motorway runs but your situation maybe different.

The MPG would drastically drop for the short journeys, mid 30's at a push but as we all know that is the nature of Diesel engines these days.

They take forever to heat up and run at the optimum efficiency.

Hopefully it'll get better, the engines don't really 'loosen' up until after 10k


Sent from my moto g(7) power using Tapatalk
Yep fully agree, although there is 50,000 miles on the car already so was a bit worried incase something wrong, will keep updated anyhow!
 

SteveGSXR600K1

Active Member
May 6, 2017
373
106
I use an app called Fuelio for my MPG calculations. Slightly more accurate than manually doing it, as you don't need to fill up to exactly the same level, etc, each time. Brimming it will just piss some of it out of the overflow when going around left bends! I find the actual MPG is usually 1-2 MPG below what the car says.
 
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Woody_72

Active Member
May 10, 2020
246
106
Northwest England
I do a lot of mileage including a lot of dual carriageways and motorways in mine and generally get 46-58 mpg on the display and I have a very heavy right foot. As people have said, check the basics - tyre pressures, are your oil and air filter clean?
 
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Feb 23, 2021
9
3
I do a lot of mileage including a lot of dual carriageways and motorways in mine and generally get 46-58 mpg on the display and I have a very heavy right foot. As people have said, check the basics - tyre pressures, are your oil and air filter clean?
Perfect sounds about right then, as stated above reset all the readings and went on a motorway drive got around 46-50mpg on a 50km drive when it was quite rainy out too so car seems to be right. maybe short journeys did have a big impact on it!
 

Woody_72

Active Member
May 10, 2020
246
106
Northwest England
If you want to scare yourself, set your display to driving data and select 'consumption' and watch it while you're pootling around locally, it's not good :oops:. If you do the same on a flat motorway while your barely feathering the throttle at 60mph it shows 70-300 mpg.
 
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