Diesel consumption increase

[mrvito]

Hi all
I'm new here so not sure where to post, so i apologize if I'm in the wrong section. I have a vito 110d, and in the last few weeks the fuel consumption has increased noticeably. I wanted to know if there is something wrong or is it just normal?
Thanks any help would be much appreciated.

 

[ringway]

Welcome aboard Mr Vito.

By how much has the consumption increased?

 

[mrvito]

Cheers mate. Id say its gone up by 15%.

 

[Will]

It has been pretty cold over the last couple of weeks, although not freezing and 15% sounds like quite a lot...

Will

 

[christopherwk]

Slow puncture?

 

[GrahamC230K]

Heavier consumption is typical in colder weather. Certainly enough to notice. I don't think a rough 10% wouldn't be unbeleiveable, we are only talking what something like 3-4mpg difference?

Dieselman can explain, I am sure I won't remember it right. Think it has something to do with the fuel, but we noted it straight away in our diesel cars.

 

[wemorgan]

Hi all
I'm new here so not sure where to post, so i apologize if I'm in the wrong section. I have a vito 110d, and in the last few weeks the fuel consumption has increased noticeably. I wanted to know if there is something wrong or is it just normal?
Thanks any help would be much appreciated.

Was this change measured over a full fuel tank?

Are you sure you did the same amount of motorway and city driving as before?

Even with these colder mornings my wife's petrol Smart car is still giving the same mgp. The biggest change comes when the engine is idling whilst I'm scrapping the ice off the windows.

 

[timskemp]

Welcome to winter diesel, for a few years me and a mate have kept stats on this and late september / early october the fuel gets changed to a winter grade, more anti-wax agent and less actual fuel. So yes, you get less MPG. In addition your auxiliary heater and electricals all use more fuel (lights, everything) and the kids going back to school means more time in traffic. Add to that extra drag from wet roads (yes, we're that sad) and we reckon it's about 8-10% worse due to the fuel and similar amount due to conditions.

Come april/may time and summer fuel will be back!

 

[st4]

yes I too have noticed from full to empty about a 10-15% drop in MPG and from best to worse given a similar avg speed, similar driving style a 20% drop. No amount of millers helps. I've noticed this last year with my diesel car and its most irritating. My pals focus diesel is also returning abysimal mpg compared to the summer.

I am now using a/c and lights etc too when i didnt but i tried without the a.c and its still worse.

 

[Dieselman]

Welcome to winter diesel, for a few years me and a mate have kept stats on this and late september / early october the fuel gets changed to a winter grade, more anti-wax agent and less actual fuel.

Do you know for sure that filling stations are stocking winter diesel. I would doubt it very much as it isn't needed until near freezing temperatures and we're only at 10c recently.

Back to the O/p's query.

A diesel engine requires approx 15% more fuel when cold for the first 1 km or so, after that it gradually reverts back to normal consumption as the engine heats up.
This contrasts with a petrol engine requiring 400% more fuel for the first 1km, etc..

What you are experiencing is increased losses from the engine and power-train as a result of colder start temperatures, thicker fluids, greater use of electrical consumers and greater heat loss from the engine as a result of lower ambient temperatures and increased use of the cabin heater.
Electrical consumers create a noticeable drain, headlamps = 1mpg, for example.

As the CDi is reasonably efficient so doesn't waste a lot of heat, why not try a radiator grille block to aid quicker warm up and lower thermal losses.
As a side effect the improved aerodynamics should assist with lesser consumption due to improving the Cd by 15-30 points.

I've not noticed any reduction in economy on my cars yet.

 

[stevesey]

yes I too have noticed from full to empty about a 10-15% drop in MPG and from best to worse given a similar avg speed, similar driving style

I thought you'd slowed down after you chat with the blonde on the M5.

As the CDi is reasonably efficient so doesn't waste a lot of heat, why not try a radiator grille block to aid quicker warm up and lower thermal losses...

Noooo .. don't open the can of worms about rad blocks and warm up time - remember it's an areodynamic aid.

 

[Dieselman]

Noooo .. don't open the can of worms about rad blocks and warm up time - remember it's an areodynamic aid.

Ah..so it is. Maybe I'll try the continental quilt method of engine insulating as well though.

 

[timskemp]

Do you know for sure that filling stations are stocking winter diesel. I would doubt it very much as it isn't needed until near freezing temperatures and we're only at 10c recently.
:

Nope, I have no hard evidence, just that the charts we used to keep showed a marked difference around october and april, too steep and regular to be down to weather.

 

[icedillon]

Weather is getting colder, are your journeys short as this will also make it worse! Cars do really need to get up to operating temp quicker these days!

 

[st4]

I thought you'd slowed down after you chat with the blonde on the M5.

Hmm this is since then. I drove down the 74 to Carlise (on way to Newcastle for a boozy weekend) 2 weeks back and at same speeds + traffic conditions the MPG was 10% worse. The trip to Carlise to surrender licence was done in warmer weather and at identical cruising speeds (well below 100mph).

I'll take wills explantion re heatloss as the cause. Makes me want to move away as this cold weather really doesn't agree with the car.