HELP - MPG just gone really shitty.

[Wheely]

My poor Leon Cupra, what have I done to her

My average MPG for a normal (eg to work - 11 miles partial commute) is always in the 40+ mpg - usually around 44ish, and 50 at a real hard push (in a slow kind of way).

Well the Sunday-before-last it all went horribly wrong. Only two events happened that weekend.

1. I had 4 x new tyres on Saturday. All Good Year F1 GSD3s. All at correct pressure. They replaced previous GSD3s (front) and Pilot Sport (rears). Their pressures are exact.

2. Used my first fill of Millers Power Plus 4 - added to a new tank of Tesco derv. Added 2 measures to the full tank.


And thats it.

MPG to work is now 33 - 36mpg. All journeys show this.
And my tank of derv, which lasts 450 - 480 miles lasted just 400 miles. So it just the fuel computer -- the fuelling really has gone toss.

This weekend (just gone) I did refill fuel, without the Millers, but it's still pants.

No other issues with cars driving etc -- have noticed virtually little or no smoke lately !!!

Really want big help here. This is naff !!!!


MARK

 

[daveyonthemove]

My advice is to do 3 things.
1. Stop buying the cheapest fuel and put some Shell extra or BP ultimate in. No point adding additives if your putting it in poor quality fuel (i'm not saying it is, but it could be!) Make sure your adding the correct quantity of millers.
2. Check the air filter for any clogging. After the crap weather we've had you might find it needs cleaning or replacing. Also check the MAF for any signs of contamination.
3. Reset the ecu. I find that if i change the way i drive or the fuel/additive i'm using it helps to reset it and start the learning from fresh.
All of these are free/cheap things that could make the difference.

 

[Wheely]

My advice is to do 3 things.
1. Stop buying the cheapest fuel and put some Shell extra or BP ultimate in. No point adding additives if your putting it in poor quality fuel (i'm not saying it is, but it could be!) Make sure your adding the correct quantity of millers.
2. Check the air filter for any clogging. After the crap weather we've had you might find it needs cleaning or replacing. Also check the MAF for any signs of contamination.
3. Reset the ecu. I find that if i change the way i drive or the fuel/additive i'm using it helps to reset it and start the learning from fresh.
All of these are free/cheap things that could make the difference.

Thanks for reply.

For item (1) I have always used Asda's and Tesco's fuel and never had an issue. I was concerned that Tescos (1st) batch may be bad, thats why I went Asda's this time and still have same mpg. And I filled with correct fill of millers.
I'll check item (2) the weekend -- although down here in the southwest we really havent had any bad weather !!!!! Just are normal excessive amount of rain.(it is due its 30K service in 800 miles time)
If I cant get anywhere here I'll reset the ECU, but for sure my driving remains constant and nowt has changed.

Ta for feedback, keep in commin'

 

[skullmunki]

Like davey said, unless your bothered about your clubcard points, go for the shell diesel extra (its the same price!) and try an ECU reset.

Daft question, but if they hadnt balanced the wheels properly or if the tracking/alignment went slightly out, would this affect the mpg?

 

[Fl@pper]

sounds daft but not recent weather affected is it ? can all add to cause/effect

defrosting - longer queues - slower traffic - colder air

etc etc etc

 

[chillcupra]

This may be controversial but reckon i noticed a decline in mpg with gsd3s.

 

[lukey]

continental reckon tyres can affect mpg, they have an ecocontact that they say gives more mpg

 

[Snoopcousins]

Funny thing, i have been thinking the exact same thing about mine for the last couple of weeks since I just got my new Eagle F1s.
At the same time though, I reset ECU for the 1st time, using Millers for the first time and im ng BP Ultimate. I used to regulary get over 44mpg or up to over 50mpg going to work, now i cant get out of the 30's!

The car is running great since reset, i did the old run through every gear using all revs for the first couple of days to get the engine to respond better to more spirited driving which was explained in another thread by someone. But since that, even when driving miss daisy I cant get my average into the 40's and im getting the least miles out of a tank that I have ever got!
Should I do another ECU reset?
Think i will also get the balancing and alignment checked too...

 

[muddyboots]

My Passat's been doing the same too. For the last few weeks it's been a struggle to break 40mpg, even when driving gently. On the same journey with the same driving style I'd normally expect to average high 40s.

 

[Jon TDI]

Fuel companies put in anti-gelling agents in the fuel over winter months to stop the diesel separating in low temperatures.
This will have an affect on fuel economy.

 

[sssstew]

thats a hell of a drop. i just cant see it being tyres or fuel or weather making that larger difference, but maybe just maybe all the factors together could mean the drop....

 

[AndyVTR]

I've not noticed anything with GSD3's and Tesco fuel.

Too many variables. Harder to get decent MPG in the cold though.

 

[ChrisUK]

Just to note to rule out weather/fuel - I havent had any drop in mpg over the last few months, in fact, if anything, I've been driving harder, and getting the same mpg (high 40's normally).

 

[AndyVTR]

How consistent is your drive Chris? In the cold it takes me half an hour to get up to 50mpg on trip (1).

 

[woodyfr]

I'm bit of a NON car tec, what is an ECU reset?

Dan

 

[Murielson]

As of yesterday got 53.73 mpg from Cordoba 1.9TDi Vario Estate for the last tank of fuel for mainly motorway commute. Use Sainsburys for fuel and been getting approx this for the past month or so since buying the car.

Hope this helps with ruling in or out weather, road conditions etc in your list of variables.

 

[sssstew]

I'm bit of a NON car tec, what is an ECU reset?

Dan

it means disconnecting the battery for about 30 mins or so then plugging back in, means the ECU will go back to all default settings and have to re-learn your driving style again.

but yes agreed with others, the winter only every effects my car by 1-2mpg less overall.

 

[Wheely]

thats a hell of a drop. i just cant see it being tyres or fuel or weather making that larger difference, but maybe just maybe all the factors together could mean the drop....

I cant help its one single thing doing this. Surely a brand new set of GSD3s is better (mpg-wise) than the old 1.7mm worn out ones (I even checked to make sure they fitted tghe direction correctly !!!)

It really was like a light switch turning on after that weekend. And as stated, here in the south west I've only had 2 or 3 frosty days, and no snow. Rain yes and lots of wind - but even though wind kills mpg, the return journey home (windward) is still crap.

I was thinking something like after the adding of millers (first time ever), it shifted a bit of smeg down my fuel line and partially blocked an injector(s). So was thinking about a double-dose of Millers and a bit of a thrash for a bit.

Need this sorting - you dont know just how sad this is. My pride and joy that's a sporty car with economy, is losing is economy status !!!!

 

[daveyonthemove]

Wont hurt to give it a good old "italian tune up".
Just make sure the engine is warm first before you give it too much hammer.

 

[davels]

I'm bit of a NON car tec, what is an ECU reset?

Dan

here you go mate a few helpful souls did a we guide explaining how and why to do one
http://www.seatcupra.net/forums/showthread.php?t=110917