Diesel owners: Loss of mpg in the recent cold?

[fjord]

Just wondering if anyone else has noticed a drop in mpg since the cold weather set in?

My 320d gives me 36mpg driving like a complete Doris. This is st to be honest but i cant be bothered to spend the time/money/effort to get to the bottom of it, and it seems like e46 diesels are a lottery as to whether you get one that does good or bad mpg.

Anyway, was wondering if this may change in summer? Maybe reach 40mpg?

I heard that diesels really struggle in this cold weather, and operate and run much better in the warmth?

Anyone else got similar issues in the low temperatures?

[All that jazz]

Yes it's normal in the winter.

[Six Fiend]

Perfectly normal behaviour

[anonymous-user]

36 mpg seems pretty low, We've had temperatures down to -16 and i'm getting about that out of my petrol is200

[thinfourth2]

Colder air = denser air = more oxygen

Combine with a heavy right foot and you use more fuel

[munroman]

If you are having an issue with the E46, check the running temperature.

I recently bought a Rover 75 Auto, with the M47R engine, they are notorious for cold running due to high thermal efficiency, compounded by the thermostat failing open, and it's a major job to change.

Someone came up with the idea of putting an inline thermostat from a Renault 5 into the top radiator hose, which I have done on 2 different 75's now, this took the OBD2 max temperature from a max of 69-71c in my cases, up to 84C.

The MPG on the Auto's computer display went from 33 to 48 on similar commuting journeys.

[DrDeAtH]

The additive package is different in winter to reduce fuel waxing. By default, it reduces consumption also.

[Schermerhorn]

My Passat gave me 62 miles (not mpg) from £20 of diesel.

Usually I can get close to 100 miles. Maybe slightly higher if more motorway travel is involved.

[Fartgalen]

fjord said:

Just wondering if anyone else has noticed a drop in mpg since the cold weather set in?

My 320d gives me 36mpg driving like a complete Doris. This is st to be honest but i cant be bothered to spend the time/money/effort to get to the bottom of it, and it seems like e46 diesels are a lottery as to whether you get one that does good or bad mpg.

Anyway, was wondering if this may change in summer? Maybe reach 40mpg?

I heard that diesels really struggle in this cold weather, and operate and run much better in the warmth?

Anyone else got similar issues in the low temperatures?

I drive like a complete Doris in my daily - a 2.4 5cyl petrol Volvo, and get around 42-43 to the gallon. Admittedly little traffic, and fast A roads.

[PaulGT3]

Yes my 2.1TD has gone from around 700 miles to a tank (45mpg) to around 600 miles to a tank (40mpg)

[lowdrag]

aany of you thought of blanking off part of the radiator? Used to be de rigeur when I was young, and then she'll run at a proper temperature and give better mpg.

[V88Dicky]

fjord said:

Just wondering if anyone else has noticed a drop in mpg since the cold weather set in?

My 320d gives me 36mpg driving like a complete Doris. This is st to be honest but i cant be bothered to spend the time/money/effort to get to the bottom of it, and it seems like e46 diesels are a lottery as to whether you get one that does good or bad mpg.

Anyway, was wondering if this may change in summer? Maybe reach 40mpg?

I heard that diesels really struggle in this cold weather, and operate and run much better in the warmth?

Anyone else got similar issues in the low temperatures?

Sweet baby Jesus!

And 7-9p per litre more for the privilege.

Time to ditch the oil burner?

My last daily, a 2.0 petrol, would do 42-45mpg week in week out and 49 on a long enough run.

[Lee540]

I'm getting an OBC average of 42mpg from my 2.0TDi 170

Haven't really noticed any difference since July, seems to be around that all of the time.

[DCLXIV]

CDB1983 said:

36 mpg seems pretty low, We've had temperatures down to -16 and i'm getting about that out of my petrol is200

Really? I've never heard of anyone getting above low-30s in one of those. I'm only getting mid20s at the moment.

[stevesingo]

http://www.bmwland.co.uk/forums/viewtopic.php?f=17...

Follow the instructions and you need to be in 7.0. This will give you a didgital temp readout on the OBC. It should be 080-090, i.e 80-90degC. If it is not, there are two thermostats that may have gone tits up. Replace both as it is not much extra work.

Very common problem.

[C.A.R.]

Tanks over the last few weeks have gone down to 52, 48mpg average. I typically get 55-57mpg. It's not only because of the cold but also due to the increased number of traffic jams caused by the traffic because of the weather!

[excel monkey]

V88Dicky said:

My last daily, a 2.0 petrol, would do 42-45mpg week in week out and 49 on a long enough run.

Good for you. Presume this was your Avensis - they are very very economical.

OP, this is normal. As others have said, diesels take longer to warm up, and on short journeys may not reach normal operating temperature at all. Also the fuel companies add anti-gelling agents to the fuel in winter, which doesn't help.

Discussed here at length a few years ago:
http://www.pistonheads.com/gassing/topic.asp?t=793...

I'm a loser and track fuel economy via the fuelly website. My wife uses our E90 320d mostly for short journeys, and the fuel economy dips by about 5mpg in winter.

[GroundEffect]

Engines run more efficiently the hotter they are. This is due to a multitude of reasons, one of which is lubrication, but also combustion temps.

[Hubris]

Not a huge difference tbh.

Try a can of bg244 in it next fill up, and an italian tune up.

[monthefish]

thinfourth2 said:

Colder air = denser air = more oxygen

Combine with a heavy right foot and you use more fuel

but on the other side of the coin, cold air = more efficient in a turbo'd engine.



36mpg driven like a doris???? Something seriously wrong there.
My 320d (E92) returns average 60mpg driven sensibly, and will near 70 if driven like a doris.



ETA (and I've not seen any drop in the recent cold weather either)

Edited by monthefish on Thursday 31st January 10:34