Reported economy in the toilet after air filter, oil and filter, and winter tyre change

[MrGreedy]

When I ran diesel cars I always noticed an increase in consumption during the colder months even though my usage pattern (25+ mile commute in each direction on fast A- and B-roads with little congestion) was unchanged. I always put that down to the switch to winter blend fuel which is normally available from 15th November to 15th March each year, as that has a marginally lower energy content per unit vvolume.

Ah, I didn't even know this is a thing. I think @ALFAitalia mentioned it earlier, but wasn't initially sure what he meant.

I could guess then that new tyres with the thicker tread pattern, a new air filter, AND winter fuel have all coincided at once! Maybe between them, this has resulted in a noticeable hit in fuel economy.

Let's see what my cruise down the M1 brings next week, through mile upon mile of 50mph speed restrictions!

 

[OneForTheRoad]

Ah, I didn't even know this is a thing. I think @ALFAitalia mentioned it early, but wasn't initially sure what he meant.

I could guess then that new tyres with the thicker tread pattern, a new air filter, AND winter fuel have all coincided at once! Maybe between them, this has resulted in a noticeable hit in fuel economy.

Let's see what my cruise down the M1 brings next week, through mile upon mile of 50mph speed restrictions!

My glc is still returning the same mpg now than it did in the summer and over the past 2 winters . I've changed air filters , all 4 tyres , to all seasons and used both winter and summer derv. 30/32 mpg combined across most journeys. Most I saw was 45mpg on a 70 mile trip to the Seahouses one summer.

The ME app is now logging data from every glc 350 in the UK and charting it , here's mine .

 

[st13phil]

Maybe between them, this has resulted in a noticeable hit in fuel economy.

In aggregate they may have caused a marginal increase in consumption, but I still think the hit you reported is too large to be explained by those changes, even in unison.

 

[OneForTheRoad]

In aggregate they may have caused a marginal increase in consumption, but I still think the hit you reported is too large to be explained by those changes, even in unison.

I find his mpg figures bizzare TBF. I've owned an e350 and glc350 , e320 and CLS 320 and didn't get any where close to the claimed figures of
Taking it super easy, 50-56 mph (to stick in lane 1 with the trucks) 70mpg.


60-65mph gives 58mpg.


70mph gives about 55mpg.


In fact I don't even think the mb engineers ever did either .

That's just being super greedy

 

[MrGreedy]

I find his mpg figures bizzare TBF. I've owned an e350 and glc350 , e320 and CLS 320 and didn't get any where close to the claimed figures of
Taking it super easy, 50-56 mph (to stick in lane 1 with the trucks) 70mpg.


60-65mph gives 58mpg.


70mph gives about 55mpg.


In fact I don't even think the mb engineers ever did either .

That's just being super greedy

"And who?" Thundered the giant
"Are you?"

"Mr Greedy" squeaked Mr Greedy.


I'll just leave this here...

Post in thread 'Mpg record ! Wow E350 bluetec'

Jul 29, 2022

Just done a 130 mile trip back from Stokesley (nice rural part of the Country York North Moors way).

Started off over 80mpg but was very flat on the motorway for the first 20 miles.

Settled around 75mpg for the next 25 miles, then hit stop start motorway traffic, going from circa 50-60 down to near zero and back up again over about 20 miles. That hammered the mpg down to about 65mpg. Then the reminder of the journey in moderate to heavy moving traffic, down past Leeds, Barnsley, Sheffield etc which it quite hilly. A stop at the services and then back parked up on the drive, and...

Ta...

• MrGreedy

• 

 

[OneForTheRoad]

"And who?" Thundered the giant
"Are you?"

"Mr Greedy" squeaked Mr Greedy.


I'll just leave this here...

https://forums.mbclub.co.uk/threads/mpg-record-wow-e350-bluetec.249799/post-3204755[/EMBED

[EMBED content="post-3204755"]

I'll just leave this here from honest John. Stats from a nation of owners.

Left side is expected mpg from mb , right side is real mpg figures.

[/embed]

 

[tonysmb]

The above figures 'prove' that the V8 500 petrol is the most 'efficient' car, achieving 94%. Therefore, the govt should be encouraging more people to drive the cars that achieve closest to the manufacturers' figures, not working from laboratory tests.

Oh the fun you can have with figures, percentages, averages etc. etc,,

 

[OneForTheRoad]

The above figures 'prove' that the V8 500 petrol is the most 'efficient' car, achieving 94%. Therefore, the govt should be encouraging more people to drive the cars that achieve closest to the manufacturers' figures, not working from laboratory tests.

Oh the fun you can have with figures, percentages, averages etc. etc,,

At least it's a realistic figure . Not pie in dee sky

 

[MikeInWimbledon]

No, it is actually all about snow. Bare roads no matter how cold are child's play. Driving in drifting snow where defining the road edges is partial guesswork is another order of magnitude more difficult. Not that I'd expect to find that in sneering Wimbledon. Really, if you've no experience of the topic, STFU.

And there we have it.

34 million cars (96%) on Britain's roads never switch to Winters.

Of the 4% that do, half of them are in Scotland. The balance are usually used by people who live in hilly, coastal or exposed areas likely to suffer from snow or black ice.

Bear that in mind in deciding whether you dare drive this week, when temperatures across the UK are expected to stay below 7 degrees, with wind chill.

I've bought three sets of Winters over the last decade from EBay Germany, where barely used winters are sold in great numbers as people switch cars, so I recommend Ebay as a source for Winter wheels.

( Note You must thave "Alpine" marked Winters to drive in frost, ice, slush or snow in Germany. The pre-2018 M+S tyres are no longer legal for ice, slush, or snow use in Germany "von Oktober bis Ostern" i.e. from October to Easter)

 

[ChrisPDuck]

The above figures 'prove' that the V8 500 petrol is the most 'efficient' car, achieving 94%. Therefore, the govt should be encouraging more people to drive the cars that achieve closest to the manufacturers' figures, not working from laboratory tests.

Oh the fun you can have with figures, percentages, averages etc. etc,,

I spotted that too. Unfortunately my E500 is currently on only 82% of the manufacturer's figure, but I don't do very many long journeys, and I'm still enjoying the right foot response a bit too much.

 

[MikeInWimbledon]

The above figures 'prove' that the V8 500 petrol is the most 'efficient' car, achieving 94%. Therefore, the govt should be encouraging more people to drive the cars that achieve closest to the manufacturers' figures, not working from laboratory tests.

Oh the fun you can have with figures, percentages, averages etc. etc,,

As we said, more than two decades ago, when the EU introduced these unrealistic benchmarks, these standardised measures don’t reflect real world patterns of use.

Diesels look better than they are because it takes too long for them to warm up on short distances.

These aren’t manufacturers’ numbers, they’re bureaucrats’ numbers: the result of unrealistic sampled tests.

And that’s all long before the major manufacturers, played the software game of “managing the numbers” to hit the Brussels model. For which they were caught out, costing VW customers €33 billion in compensation and regulatory fines.

 

[MrGreedy]

At least it's a realistic figure . Not pie in dee sky

Okay, maybe a different way to ask the question could be this:

After changing old winter tyres to new winter tyres, an oil change and an air filter change, what could cause the reported economy on the dash to drop by 25%?

So even if that's assuming it's gone from pie in dee sky figures to correct now 'correct' figures, what would cause that shift?

Something has changed in ECU mpg calcs, and it surprised me.

 

[ChrisPDuck]

Are your new tyres the right size? I'm struggling to figure out which way the figures would be skewed, but a different sized wheel would certainly affect the ECU mpg calculations.

A bigger than expected wheel would mean the car has to travel further for the same number of revolutions (which is all the ECU knows about), and travelling further would require more fuel - so I reckon a slightly deeper tyre would cause a drop in reported mpg.

 

[MrGreedy]

Are your new tyres the right size? I'm struggling to figure out which way the figures would be skewed, but a different sized wheel would certainly affect the ECU mpg calculations.

A bigger than expected wheel would mean the car has to travel further for the same number of revolutions (which is all the ECU knows about), and travelling further would require more fuel - so I reckon a slightly deeper tyre would cause a drop in reported mpg.

Tyres are the same size and spec (or better) as those that came off.

Details in post #6

Post in thread 'Reported economy in the toilet after air filter, oil and filter, and winter tyre change'

Dec 4, 2024

Tyres ?

Poor ratings and very noisey!

View attachment 164836

Yes, they are not the best compared with summer or all season tyres, but they are full winter tyres for grip and this is compared with the winter tyres I've just replaced. I don't notice any noise difference except on concrete motorway, where if I listen carefully I can possibly detect a hum/buzz that maybe wasn't there before, but this is a 'can I hear something worse, I'm not sure?' level of noise, so not significant.

In 245/45/R17 the tyres are reported as:

Hankook iCept Evo 3
C for fuel
B for wet grip
72 dB for noise

Conti...

• MrGreedy

• 

 

[rf065]

So, to the original question, could changing from one winter brand of tyres to another winter brand of tyres (see posts at beginning of thread for details and tyre ratings) cause an enormous drop in economy?

At this point the virtues of winter tyres is not worth discussing, as they are on my winter alloys and I'll run them over the winter, swapping to summer alloys and tyres in the Spring.

Regarding the tyre labelling, there is no independent testing, the manufacturers test their own tyres and come up with their own tyre labelling info.
I wonder how many are 100% truthful?

 

[OneForTheRoad]

Okay, maybe a different way to ask the question could be this:

After changing old winter tyres to new winter tyres, an oil change and an air filter change, what could cause the reported economy on the dash to drop by 25%?

So even if that's assuming it's gone from pie in dee sky figures to correct now 'correct' figures, what would cause that shift?

Something has changed in ECU mpg calcs, and it surprised me.

I've no idea tbh. Possibly fuel temperature sensor fault , that's how VW's were tricked into extra horse power and bull$hit mpg readouts.

 

[colinallcars]

Apologies if this has already been covered. Have you done a brim to brim calculation?

 

[OneForTheRoad]

Apologies if this has already been covered. Have you done a brim to brim calculation?

Id estimate hes still using diesel he put in during 2022 tbh. @ 80 mpg .

 

[MrGreedy]

Id estimate hes still using diesel he put in during 2022 tbh. @ 80 mpg .

Hilarious and intelligent input.

I'm looking for ideas about why the sudden change in reported economy. Repeated jibes isn't it.

I'll see how things go since the adaptation reset, as without any fault codes, I think it's a little too soon to be chasing down a fuel temperature sensor coincidental fault. Although nothing can be ruled out.

 

[OneForTheRoad]

Hilarious and intelligent input.

I'm looking for ideas about why the sudden change in reported economy. Repeated jibes isn't it.

I'll see how things go since the adaptation reset, as without any fault codes, I think it's a little too soon to be chasing down a fuel temperature sensor coincidental fault. Although nothing can be ruled out.

Sorry , but it tickled me that someone driving a v6 3 litre thought he was getting 70+ mpg . I don't think there's an issue with the car now , I'd suspect it's giving you the correct mpg figures. I'll get me coat .

I'll leave you with this .

Average fuel consumption is calculated from the amount of fuel injected within a specific period. If the display is reset it can take approx 2min or 4km for sufficient data to be collected in order to display the data correctly. This would suggest the data is collected real time and not read from a map?

WIS shows the consumption signal is generated by the ME-SFI/CDI control unit (N3/10, N3/9) and the distance travelled by the four wheel speeds. Signals come from the traction control unit N47

So it's my thinking your previous wheel set up was incorrect for the car if n47 was playing a part. Or you disturbed an ECU connection?

Can you confirm tyre sizes for both sets and rim sizes .