During the recent period of sub zero temperature (ranging from -1 to -12 deg-C), I noticed a maked decline in mpg.

I realise that driving in icy and snow conditions involve lower gears so for any given engine rpm the vehicle forward speed will be lower, and therefore the mpg will lower. However during a few opportunities to drive at speed in 4th , as I do mostly on local roads, the mpg was definately much less than normal.

Would adding a radiator grill cover be beneficial?

Has anyone else with the diesel engine noticed a big drop in mpg during the cold?

My car is a diesel 2.0 litre 110bhp

Normally average 48mpg, mostly A & B roads, not much city driving; during the cold spell averaging about 40mpg.

Comments?

Yep -agreed!

I average usually 44-46 in normal driving brim to brim except when carrying my PA kit in the car for a month when it fell to 42!!

However, in the cold, and on the hills, it fell to 38. Quite a noticeable difference.

The cold could be the reason my DSG140 doesn't seem that economical....or 900000's either.

Mike

This is real world mpg and the weather affects it significantly when really cold. It does the same with my petrol yeti as well, and most of the other cars I've owned. It should improve with higher temps. Modern efficient engines don't produce as much wasted heat, so take longer to warm up and that hammers the old mpg. It should average out over time and I bet that engine will do wonders when its nice and warm.

During the recent period of sub zero temperature (ranging from -1 to -12 deg-C), I noticed a maked decline in mpg.

I realise that driving in icy and snow conditions involve lower gears so for any given engine rpm the vehicle forward speed will be lower, and therefore the mpg will lower. However during a few opportunities to drive at speed in 4th , as I do mostly on local roads, the mpg was definately much less than normal.

Would adding a radiator grill cover be beneficial?

Has anyone else with the diesel engine noticed a big drop in mpg during the cold?

My car is a diesel 2.0 litre 110bhp

Normally average 48mpg, mostly A & B roads, not much city driving; during the cold spell averaging about 40mpg.

Comments?

Apparently it's normal to see a drop in mpg during the winter. Combination of winter diesel with additives to reduce tendency to freeze giving lower economy, lower ambient temperature means it takes longer for the engine to get to optimum operating temperature and it's using more fuel until it does get to optimum, lights, heater, bum warmer etc all adding to the consumption. Light a fire under the engine block and fuel tank to warm things up, you'll see an improvement in economy.

Stewart

This is real world mpg and the weather affects it significantly when really cold. It does the same with my petrol yeti as well, and most of the other cars I've owned. It should improve with higher temps. Modern efficient engines don't produce as much wasted heat, so take longer to warm up and that hammers the old mpg. It should average out over time and I bet that engine will do wonders when its nice and warm.

Nigel - good to hear you. Hope you had a good time over Christmas.

Do you mean higher engine temps or higher ambient temps? I was expecting more from Elsie on the trips up and down from Scotland.

Mike

Personally, I think it's a change in the diesel spec for winter (additives added for the cold weather etc), the Yeti (and the Fabia vRS before it) suffers at least a 5% MPG drop off come November or so then March time it magically reappears. There may be an element of engine warm-up time involved as well but the sudden decrease/increase doesn't always tie in with cold ambient temps.

Edited 31 December, 201015 yr by aerofurb

But for my Scotland jaunt the car was running at motorway speeds for about 8 hours over a 10 hour period for both waysa, so I was hoping for better mpg, as I was only doing max indicated 70-75mph where possible.

Mike

Hi Mike, glad the Scotland trip went well, enjoyed the write up on that.

Ambient temps are what I meant, as once warmed up, the engine temps should be fairly constant. Yes, winter additives in diesel bring it down a little, but every diesel I've run in winter has reduced mpg in line with the cold. Ancillaries like heated seats impact slightly, but doubt if it would have a massive effect at motorway speeds. Aerodynamics of the Yeti aren't the slipperiest, so higher than say strict legal limit, and things are likely to change mpg wise. If you've been running through snow drifts and such, that will tend to bring it down a little as well, so it all adds up.

Couple those factors with a brand new engine and there is scope for a big chunk of improvement. My last 2.0 PD engine was absolutely terrible when it was new, barely cracking 40 mpg, after around 1000 miles, on a run. That improved to about 44 or 45 on a good day at fairly swift motorway speeds.

The maxidot readout appears a lot more accurate than the readout on my old Altea, which was a good 6mpg out. At least that's what I've observed so far, maxidot is only 1 or 2 different to what I'm calculating on brim to brim fills.

We'll see what the new maps do to things pretty soon I guess Mike.

Weather (wind, rain etc.), temperature, air density and altitude will all play a part besides what they put in the fuel.

You may notice that even when the engine coolant reaches temperature the oil particularly on a cold day takes much longer to reach it's operating norms. This will be similar for other oil based bearings in the drive system, which all increase frictional losses. Then you have cold tyres again taking time to warm up with yet more losses due to slight deflation and there's air density which effects drag (aerodynamics).

The list goes on :S

TP

hi all,

i agree that driving in winter conditions will lower the average mpg because of lights, heaters, demisters all being on (and all the other stuff mentioned above) but i reckon you've all missed something.

the average consumption is calculated from the moment the engine is started to the time it's switched off again.

how long is your engine running while you scrape ice and defrost the windows before you set off?

i reckon mine is about 5mins.

if you are only doing a relatively short journey then stationary running time will have a large effect on overall mpg.

even on a long trip it can take many miles for the mpg figure to sort itself out.

i regularly drive to birmingham and the 1st half of the trip is on A roads averaging 55 to 60 mph, then 2nd half on the motorway normally at about 75mph.

i've seen an average 50mpg before joining the motorway, but this quickly drops to 42mpg average at the end of my journey.

the return trip seems to work in reverse.

42mpg on the motorway but it takes until i'm nearly home for the figure to rise to just 46mpg average for the whole return trip.

it's a time/fuel economy conundrum.

i would rather sacrifice a few mpg to get there in a reasonable time if it's just a weekend trip.

however on a week or two away i would take a chill pill and stick to the A and B roads.

Edited 31 December, 201015 yr by YetiClive