TDI Economy down since recent cold weather, why?

[pietch]

My 1.4 TDI mpg is down about 20% since this spout of cold weather, why? Perhaps I just need an air filter change? Could it be something else?

Thanks all!

[Td-eye]

If you are just doing short journeys it's likely because the engine requires more fuel when it's cold and it takes longer to warm up in the winter.

[ap0gee]

Originally Posted by Td-eye

If you are just doing short journeys it's likely because the engine requires more fuel when it's cold and it takes longer to warm up in the winter.

You should find that your economy is BETTER on longer journeys when it's cold, because the increased density of cold air allows more efficient combustion within the engine (and improved intercooler performance in your case too!)

[ScoobyChris]

We're also on winter diesel at the pumps now which doesn't result in as good fuel economy as "summer" diesel

Chris

[mluton]

Same with my petrol vRS, economy has shot down on my short runs.

[Dr Zoidberg]

And having the lights and heater on full will also cause a drop in economy

[P-A]

I've noticed this too. I drive 80 miles a day (ie. no short journeys) and the economy has fallen by around 15-20% in the last month or so.

[mannyo]

I have noticed the drop on short runs, my TDI seems to take about 10 miles before it warms up. Once going though it seems about the same, for the remainder of the journey home from work 58MPG is still achievable depending on traffic. I am still getting 560 miles per tank.

[WW_VRS]

The heater takes most of the energy, I drive with dipped beam on 100% of the time and although they are Xenons so they use about 20W/side less compared to standard bulbs, I doubt that's gonna make much difference.

The warm-up time of the engine is the biggest loss on both petrol & diesel cars + the winter fuel

[anonymouse]

Just checked mpg (brim to brim method) after 1st 300 miles of Fabia vRS ownership.
39 mpg - but no journey has been over 10 miles and mostly in urban i.e. slow traffic conditions.
As everyone says - cold, warming up time, heater & lights, winter diesel.
Old Cavalier used to drop to 36 mpg this time of year, 40 to 42 rest of year.

[ap0gee]

Originally Posted by WW_VRS

I drive with dipped beam on 100% of the time and although they are Xenons so they use about 20W/side less compared to standard bulbs, I doubt that's gonna make much difference.

An redcution of 40 Watts on a car whose engine produces 95,000 Watts - wouldn't worry about it! Then again, they produce a lot more light, so when Newton's 3rd law of motion and Einstein's special theory of relativity are taken into account, xenons probably slow the car down MORE than convention filament bulbs...












*guess who's just been down the pub for a pre-Christmas pint *

[WW_VRS]

I'm just gonna have to crack open a can to recover from that

[devonutopia]

My car has actually failed to reach 90 degrees on the needle for my whole commute on occasions, as its so gentle.... Brrrrr!

Fuel economy has been in mid 40s as a result too, as it's obviously working harder, and I get lots of pale white smoke for the first 30 seconds or so of setting off for work.

[WeirdKerr]

Originally Posted by ScoobyChris

We're also on winter diesel at the pumps now which doesn't result in as good fuel economy as "summer" diesel

Chris

winter diesel????

[bmjb99]

Originally Posted by WeirdKerr

winter diesel????

The oil companies change the composition of both petrol and diesel according to the time of year.

I don't know that it's so much of a problem nowadays, but my father was a lorry driver and occasionally in very cold weather he would be "stranded" after stopping overnight because the diesel had solidified in the fuel lines.

[WaveyDavey]

I noticed on a trip to Skeg-Vegas today that my fuel economy was less than usual..... Mind you i just put it down to the fact that just about the whole journey there and back was done with headlights, front fogs & rear fogs on along with the heater / blower going all the time and the rear window heater on for a couple of 15 minute spells too.....

Originally Posted by ScoobyChris

We're also on winter diesel at the pumps now which doesn't result in as good fuel economy as "summer" diesel

Chris

Am i being a gimmer here when it comes to 'winter diesel'???? Is it real or have i just fell into the trap???


I'll get mi coat.


Cheers

Dave.

[anonymouse]

You've not been had.
Did a quick Google just to check my facts :-

Winter Diesel

"What is FarmDIRECT winter fuel?"

In basic terms winter fuel is normal diesel but with an additve mixed at the terminal to bring the freezing point of diesel (when waxing begins to occur) down to minus 12 degrees. This is an industry-wide standard, and is important to make sure consumers in colder regions such as Central Otago and higher altitude region do not suffer from waxing effects of diesel.

"When does FarmDIRECT winter grade fuel get delivered?"


This varies from year to year, but on the whole winter grade diesel usually begins around the last week of March to the first week of April depending on condtions, and ceases around the first week of October, once again depending on weather conditions.

"What if I still have problems with diesel waxing?"

If you are experiencing problems with diesel becoming "waxy" even after the winter fuel is in use, there are still options to reduce the problem. Examples of customers adding kerosene to diesel tanks is a common occurrence, but the rate and the added costs far outweigh the benefits gained. One low cost option is if you are in a high altitude area and have had problems with waxing fuel, is to find an alternative position for your storage tank.

There are also additives that may be added to your farm tank when filling with diesel. These additives once added are proven ways of lowering the freezing point of diesel to a maximum of -25 degrees.
-----------------------------------
What has also to be factored in by the petroleum companies is that in very severe conditions 'wind chill' (that much bandied term) comes into effect. Below zero degrees for every 1 mph the temperature effect on an exposed object is a drop of 1 degree, which is why moving vehicles have been known to grind to a halt as exposed fuel lines will be affected.

[Emily-Elizabeth]

Surely diesel is very changeable depending on temperature. In hotter weather it expands more, colder weather it is more compact. That is why I would never fill my overflow tank on a hot day.

My car seems to pack a lot more punch in the cold weather, I always assumed because of the colder air combined with the more concentrated diesel meant that the car was more efficient at burning.

At the moment I am getting about 40mpg, that improves to about 45mpg in hot weather. I only use ultimate and have taken to adding cetane improver as well.

My length of journies reamin unchanged.

[Decron]

Originally Posted by Emily-Elizabeth

Surely diesel is very changeable depending on temperature. In hotter weather it expands more, colder weather it is more compact. That is why I would never fill my overflow tank on a hot day.

Not as much as petrol, but a wise precaution

Originally Posted by Emily-Elizabeth

My car seems to pack a lot more punch in the cold weather, I always assumed because of the colder air combined with the more concentrated diesel meant that the car was more efficient at burning.

Indeed. The air is significantly more dense meaning the combustion is more efficient and produces more power per unit of mixture although I doubt the density of the diesel will effect it either way as the fuel is heated anyway.

Originally Posted by Emily-Elizabeth

At the moment I am getting about 40mpg, that improves to about 45mpg in hot weather. I only use ultimate and have taken to adding cetane improver as well.

That must be costing you a fortune. You really don't need both, I would can the Ultimate (Loads of threads about it. I have never seen any benefit from using it and I doubt it could ever justify it's price over supermarket diesel which is not that different anyhow) and just use the cetane booster in moderation.

[devonutopia]

You know? I'm soooooo drunk I don't care what goes in my fuel tank..... Gents... put your cox away!

[Emily-Elizabeth]

Originally Posted by devonutopia

You know? I'm soooooo drunk I don't care what goes in my fuel tank..... Gents... put your cox away!

MUST QUOTE THIS BEFORE HE DELETES IT WHEN SOBER CLASSIC JASON!!

Jason is w@nkered, Jason is w@nkered.

Lalalalala

[vRSLen]

Well done Jason!

[Emily-Elizabeth]

Originally Posted by Decron

That must be costing you a fortune. You really don't need both, I would can the Ultimate (Loads of threads about it. I have never seen any benefit from using it and I doubt it could ever justify it's price over supermarket diesel which is not that different anyhow) and just use the cetane booster in moderation.

Nah... I like the ultimate, it creates less smoke out the back and seems to sort of snap a little more. The cetane stuff was given to me the other day and only run one tank full of it so far. Not sure yet.

I get about 100 miles for every £15 I put in, so I am happy with that really.

[anonymouse]

Cetane improver - injector cleaner
Miller Oils Diesel PowerPlus - even the wife can tell when it's not in the tanK (and that is something not to be scoffed at), seriously, for it to be so noticeable I reckon it must be adding 10 to 15 % extra power !!!! On the old Cavalier if it was not added the car felt sooo sluggish.

Improves mpg or performance - trouble is you tend to use the extra performance, but it is very noticeable, engine quieter, acceleration better (recommended it to loads of friends and not one has been dissappointed, mechanic now recommends it to diesel owners).

Forgot, Cavalier went through every MOT with 'astonishing' results due to PowerPlus - right up to 200k.

[WW_VRS]

Mine likes Diesel Extra - also my wallet prefers it by 7p / liter vs the BP Ultimate stuff in this area

When generic derv was about the same price I used BPU for a while and yes it is good, but too expensive by a mile unfortunately, and really I dont like to pay 7p / liter more for it, even though it smokes less