Hi 

Where do I start 

For the past few months the car has been returning bad mpg figs from average of 55 down to just over 40 

So things that's been done 

1 code read no faults found 

2 carbon clean made it a bit quieter but no improvement in mpg 

3 another code read and vacuum test again nothing 

4 got myself a second hand maf again no change 

5 unplugged o2 sensor. result car drove better and got better mpg so thought great o2 sensor knackered so got a new one fitted it but once fitted mpg back down to 40 ish 

So at my wits end with this car so what would make my car run better with the o2 sensor unplugged!

Sticky brake calliper? 

On 3/30/2018 at 12:44, Hartsvrs00 said:

Hi 

Where do I start 

For the past few months the car has been returning bad mpg figs from average of 55 down to just over 40 

So things that's been done 

1 code read no faults found 

2 carbon clean made it a bit quieter but no improvement in mpg 

3 another code read and vacuum test again nothing 

4 got myself a second hand maf again no change 

5 unplugged o2 sensor. result car drove better and got better mpg so thought great o2 sensor knackered so got a new one fitted it but once fitted mpg back down to 40 ish 

So at my wits end with this car so what would make my car run better with the o2 sensor unplugged!

Hi what engine do you  have this may help to identify the problem .

2.0 170 cr. 

Are these MPG figures from the on board computer or calculated brim to brim??

 

So after this week maybe warmer weather and no more Winter Fuels delivered to filling stations until Oct / November.

 

So brim the tank and see how many miles to the litre it does through the Summer.

 

?

When did it last get actually 55 mpg,  or 550 miles for 45.6 litres of fuel.

Edited 31 March, 20188 yr by AwaoffSki

2 hours ago, FatblokeVRS said:

Are these MPG figures from the on board computer or calculated brim to brim??

 

This is from the computer 

6 hours ago, AwaoffSki said:

So after this week maybe warmer weather and no more Winter Fuels delivered to filling stations until Oct / November.

 

So brim the tank and see how many miles to the litre it does through the Summer.

 

?

When did it last get actually 55 mpg,  or 550 miles for 45.6 litres of fuel.

Didn't notice the problem till the new year and the car has a 55 litre tank. And I have brimed the tank so will see how many miles I get

You can't trust the computer, it's just a guide. Always brim it to get an accurate average. Hopefully it's shows there is nothing to worry about.

On 30/03/2018 at 12:44, Hartsvrs00 said:

Hi 

Where do I start 

For the past few months the car has been returning bad mpg figs from average of 55 down to just over 40. 

Due to a daily commute of 4 miles each way my average fuel economy recorded by Fuelly is 40-44mpg.

 

In November last year I had several long journeys of over 50 miles so would have expected a higher than normal fuel return, instead Fuelly quoted 34.5mpg.

 

My vehicle was later diagnosed with a sticking front brake caliper. I didn't notice anything on any of my daily short  journeys, but did on two of the long journeys (they were just a few days apart). The drivers side front wheel made a ticking sound the same as when the engine is cooling down, and I could feel it was slightly hotter  than the other wheels. The clincher was on  the last long journey when I returned at night and saw the disc brake was glowing amber. 

 

If I hadn't have undertaken those longer journeys, the sticking caliper probably wouldn't have been diagnosed until it went for its service in March of this year. 

 

 

When it gets colder around 5 degrees mine tends to drop down to 43/46 mpg then when around 10 degrees its back up to 48/50 mpg as said above winter diesel will be phased out now for the summer so mpg should rise for everyone.

Everyone's fuel economy / MPG / Miles per litre does not drop with Winter Spec Diesel from November to April if they do long journeys and the weather might be around 0*oC.   Some people get better fuel economy in nice cold / clean air on cold roads with less traction / friction.

 

Maybe if they do short journeys, engines / oil not getting to efficient operating temps, use time warming up / deicing etc they use more fuel.

If the UK Transport / Business / Private fuel use increases 5 months every year because of Winter Formula Diesel & Petrol even where the weather is not that cold 

then that will be well documented someplace.

Interesting , I have 1.6 TDI and on my last journey I had 46 miles ( my calculation ) , Got the car 6 months ago and always was around 40s .

Today for the first time I saw over 50 reading from computer do I need to worry about something ? 

2 hours ago, Gregorry said:

Interesting , I have 1.6 TDI and on my last journey I had 46 miles ( my calculation ) , Got the car 6 months ago and always was around 40s .

Today for the first time I saw over 50 reading from computer do I need to worry about something ? 

I get 50's from a 2.0 pd with 4x4 so I would have thought 40's from a 1.6 is a little low even around town.

7 hours ago, Gregorry said:

Interesting , I have 1.6 TDI and on my last journey I had 46 miles ( my calculation ) , Got the car 6 months ago and always was around 40s .

Today for the first time I saw over 50 reading from computer do I need to worry about something ? 

 

I have the same engine and the in-car computer reads mid 40s for short journeys in town during the cold part of the year. Journeys over 10-15 miles with a warm engine brings this into the low 50s.

During the summer months I get around 56 mpg on fast motorway trips and over 60 on long A road trips. Best I have had on long non motorway journeys is over 70 on the display.

My long term actual average over three years is 55 mpg.

 

This engine gives little engine braking so good anticipation in traffic brings noticeable rewards. 

There are all kinds of driving in town.

If someone brims the tank and then does 10 journeys of 4 miles with a cold start every time and then brims the tank it is doubtful they will use the same fuel as doing 4 journeys of 10 miles in the same town.

 

When someone brims a tank and then sets off and the Average MPG is showing 70 mpg after about 70 miles maybe go in and fill up and see if it takes 4.546 litres or less to brim it.

 

Nobody has sold Imperial Gallons in the UK filling stations for years, it is a pity that people never say how many miles to the litre they get, 

or that the UK ever went properly metric with Kilometers on road signs and km/h's and km, it is odd that pricing is for a litre and the cars show MPG's, 

& that is Imperial MPG's.

3 hours ago, pikpilot said:

 

I have the same engine and the in-car computer reads mid 40s for short journeys in town during the cold part of the year. Journeys over 10-15 miles with a warm engine brings this into the low 50s.

During the summer months I get around 56 mpg on fast motorway trips and over 60 on long A road trips. Best I have had on long non motorway journeys is over 70 on the display.

My long term actual average over three years is 55 mpg.

 

This engine gives little engine braking so good anticipation in traffic brings noticeable rewards. 

Never seen 60 on my computer ..... even 2/3 h journeys , cold engine 35 ish then go up to low 40s  , city drive 43 is good on normal days  , hmmmm maybe I should go for a proper service ? 

1 hour ago, AwaoffSki said:

Nobody has sold Imperial Gallons in the UK filling stations for years, it is a pity that people never say how many miles to the litre they get, 

or that the UK ever went properly metric with Kilometers on road signs and km/h's and km, it is odd that pricing is for a litre and the cars show MPG's, 

& that is Imperial MPG's.

Yep same here , Im from Poland and it took me a wile to get use to it , 

51 minutes ago, Gregorry said:

Never seen 60 on my computer ..... even 2/3 h journeys , cold engine 35 ish then go up to low 40s  , city drive 43 is good on normal days  , hmmmm maybe I should go for a proper service ? 

 

You say you have only had the car a few months, so you have not experienced summer driving yet. I never see more than low 50s during the winter.  Watch how it improves in the warmer weather with summer grade diesel.

I hope so   Yes I had a car for about 6 months got it in autumn