poor fuel consumption

[Jamiegall1993]

Hi folks,

Purchased my 2019 seat Leon fr 190 in September.
For the second time I’ve had a sudden massive decrease in MPG.
I average around 35mpg day to day, this has halved to about 17-20mpg. No changes in driving habits. Same thing happened just before Christmas, managed to fix it by getting a “fuel system clean” by a local garage, they added something to the tank and did something the oil.
Same thing has happened again. My question is does anybody else experience this same issue?
My assumption is that I may need to start using the “super” fuel at the petrol station. I was certain that I could use the basic stuff but perhaps not.
Anybody have any advice?
Cheers

 

[Mo_86]

I have same car in ST form, when the car regens i get bad mpg too. Have you noticed your turbo whistle now louder?
Once the regen completes the sound does go back to normal.

 

[Jamiegall1993]

Hi mate,

I’m assuming you mean the FR and not ST?it’s the FR that I have.
The turbo *might* sound louder, I’m not 100% but I did notice a noise like that last night.

 

[Mo_86]

Yes mine is fr st, st as in estate

 

[Jamiegall1993]

Aw ok mate sorry didn’t realise that was its name!
It could be coincidence but I’ve put a fuel cleaner through the tank and the mpg is improving. I’m still unsure as to what’s actually causing it whether it be regen or whatever.
What kinda of fuel do you use? Just regular or super?

 

[Mo_86]

Regular shell and esso, i stay away from the supermarket stuff.
My driving is mainly around town so i see low 30ish mpg.
I also sometimes have a heavy foot so that doesnt help.

 

[SRGTD]

@Jamiegall1993 - When the GPF / OPF goes through an active / forced regeneration, I’ve found it has a very noticeable impact on fuel consumption in my VW Polo GTI+ (also has a 2.0 litre EA888 engine, but slightly higher power output; 200ps / 197bhp). Fuel consumption worsens by around 30-35% while the regen is in progress, but back to normal once it’s completed). Active GPF regenerations use additional fuel to aid burning off of particulate matter in the GPF, hence the worsening in mpg. I’d suspect that might be what’s happening with your car.

What‘s your mix of journey types? If you’re doing quite a high proportion of short / town journeys when the engine’s not getting up to optimum temperature, you’ll get more frequent active GPF regenerations than someone doing mainly long(er) ‘A‘ road / motorway higher speed journeys on a fully warmed up engine.

On long(er) journeys when the engine’s up to temperature, regenerations are likely to be passive as the very high exhaust temperature should be sufficiently hot enough to neutralise the accumulated particulate matter in the GPF without needing to use additional fuel. So passive GPF regenerations shouldn’t have a significant - if any - impact on mpg.

Tell tale signs of an active GPF regeneration taking place in my car are;

• Louder exhaust note
• A slight ‘lumpiness’ in engine idle and slight hesitation under acceleration
• significant deterioration in mpg
• A hot smell
• Engine fan running
• Stop / start won’t operate

The whole active regeneration process in my car lasts around 20-30 minutes. If the process is interrupted by switching the engine off, it will recommence when the engine’s next switched on, so increased fuel consumption will also affect that next (and subsequent) ignition cycle(s) until the regeneration has finished. If I’m aware a GPF regeneration is in progress when I’m about to reach the end of my journey, if possible I’ll extend the journey until it’s completed to save having to go through the regeneration process during the next journey.

 

[Tester01]

Let me know if you figure out your issue, interested to see it’s your GPF/OPF like mentioned above or something else