I've had my 65-reg Scout for more than 18 months and I think it's brilliant. However I've noticed that my 2.0 TDi 150 engine appears to be adversely affected by temperature so that it's around 10% worse in colder conditions even when warmed up and on longer runs. For example, this last week I've been touring with a caravan on the hook and averaged an indicated 28 mpg with the ambient temperature about 11 deg. C. The oil temperature ran about 107 deg C. In summer I usually average about 32 mpg towing - same caravan with identical load, same driver and passenger, similar roads. Not towing the average is 45-50 in winter, 50-55 in summer on longer runs. Has anyone else noticed this? The car has recently been serviced and no fault found. Is this just a characteristic of this engine?

 

I previous ran 2WD 1.9 TDi 105 bhp Octavia estates for 14 years but didn't notice any difference between summer and winter motoring.

This last 10 days in the UK Winter Spec Diesel has been getting delivered to filling stations in Scotland and the North or England, maybe further South as well.

Not that it makes anything like 10% worse economy.

 

?

Where are you that you have had colder weather conditions & how cold are you talking?

 

When weather does get much lower then obviously vehicles do take longer to warm up, 

and then they often run better when up to temp with nice fresh air, which is what Intercoolers are trying to achieve anyway on TDI's.

I live in the Midland in the UK so it's not Arctic weather here. Indeed it hasn't been very cold in the last 2 winters but clearly it's colder than in summer months. I've allowed for the fact that the Octavia does take a while to warm up (around 5-6 miles for the oil to get hot, way longer than the water temp getting to normal) so I only take note on longer runs. As this is the first 2.0 VW TDI-engined car I've had I just wonder whether this engine is more adversely affected by temperature?

My 2.0TDI 150ps takes 6 miles to get 50*oC showing for the oil when the Ambient Temp is 15*oC and lower, and is only showing 80-90*oC after about 15 miles.

20 Miles and going quick before it is near 100*oC or more.

 

Filled with Winter Diesel a week past Thursday and got better than the 10 miles to a litre i normally get and more than a year ago when the car was new. Normally i do 630 miles and fill up takes 63 liters, then last week did 710 miles in cooler weather but lots of Average Speed Camera Miles A90 & A9 and then 64 litres was all it took.

15,000 miles on since last November now and no Oil or Filter change.

Edited 28 October, 20178 yr by Headinawayoffski

I find that it is noticeable, possibly a result of lower temperatures (I understand the diesel gets thicker?) and a move to the winter diesel blends.

 

Looking at my Drivvo data the mpg in the cold weather is noticeable. 

Normal commute I get around 56mpg, up to 69mpg over a long drive (but I only tend to do these in the summer months anyway), winter time my mpg is usually between 46-48 mpg on the same runs.

 

Could be due to the extra use of the heating system, heated wing mirrors and rear window etc; but the cold temperatures do make a difference for my economy; takes longer for the car to warm up also in a similar way to Headinawayoffshi has stated.

My previous car used to average around 26mpg on the open road and 22mpg on my then commute to work - but during a snowy winter that dropped to 16mpg.

 

Cold weather and stop/start commuting equals higher fuel consumption.

^^^ The Stop / Start does not increase the Fuel Consumption if Stop / Start is working, 

but then on short trips in winter in Stop / Start traffic the Stop / Start will likely not be functioning much, and then it is Winter, Oil cold, 

vehicle not running at efficient temps.

 

Hence why Diesel Passenger vehicles, especially non efficient ones in the real world in real weather will be banned in the 'Next 2 decades or so', 

But then that is the right thing surely,  Taxi sized vehicles with 5,6,7 seats sitting polluting with 1 or 2 people in them.

 

PS,

Snowy weather is often not as cold as frosty / icy weather.....

All the gear will be on though maybe, lights, heated screens, mirrors, radio, phone charging, and stop start disabled by the driver.

Edited 29 October, 20178 yr by Headinawayoffski

29 minutes ago, Headinawayoffski said:

^^^ The Stop / Start does not increase the Fuel Consumption if Stop / Start is working,

Sorry for the confusion I meant stop/start TRAFFIC not the stop/start function.

 

I'm well aware that the intention of the stop/start function is to reduce emissions (in the official tests) and decrease fuel consumption (in the official tests).

I understood, the Stop / Start traffic meant the traffic,  what i am saying is that on cold frosty heavy air mornings and evenings like the next 5 months maybe, 

the Stop / Start does not function so the Governments allowed the Manufacturers to have the Kidology of Stop / Start where it is not able to function on lots of vehicles, 

and then on cars that the keeper got lower VED on up to before April because there was Stop / Start at Type Approval / EU Approval testing, 

but it can be disabled.

I usually have the Octavia stop/start enabled, also have the climate control enabled all year round set at 20 deg C. As my journeys are similar summer and winter then I guess the difference between summer/winter fuel consumption is mainly due to the engine (and oil) taking longer to get hot. It's useful to have the feedback from other Octavia owners to see that I'm not alone in getting better fuel consumption in summer.

 

Time was when I was getting 28 mpg average in summer when i had a dreadful Morris Marina 1.8. Also a Morris 1000 towing a caravan used to return about 23 mpg so it just shows how good modern engines are when the Octavia is capable of much better consumption.

Leaded fuel was wonderful stuff really, 2, 3 & 4 Star and a couple of shots of Redex.

Obvious people are dying now from cancer and also asbestosis from the days that brake linings were made of asbestos, 

but they were good old days.

Diesels getting Oil and Filter changes every 3,000 miles and petrols getting Multigrade every 6,000 miles.

Edited 29 October, 20178 yr by Headinawayoffski

1 hour ago, Headinawayoffski said:

Leaded fuel was wonderful stuff really, 2, 3 & 4 Star and a couple of shots of Redex.

I remember National Power which was 5 Star, 101 octane IIRC?

On 28/10/2017 at 17:33, JohnGarth said:

I've had my 65-reg Scout for more than 18 months and I think it's brilliant. However I've noticed that my 2.0 TDi 150 engine appears to be adversely affected by temperature so that it's around 10% worse in colder conditions even when warmed up and on longer runs. For example, this last week I've been touring with a caravan on the hook and averaged an indicated 28 mpg with the ambient temperature about 11 deg. C. The oil temperature ran about 107 deg C. In summer I usually average about 32 mpg towing - same caravan with identical load, same driver and passenger, similar roads. Not towing the average is 45-50 in winter, 50-55 in summer on longer runs. Has anyone else noticed this? The car has recently been serviced and no fault found. Is this just a characteristic of this engine?

 

I previous ran 2WD 1.9 TDi 105 bhp Octavia estates for 14 years but didn't notice any difference between summer and winter motoring.

it was 9 degrees today and i noticed a drop in economy by 7mpg. I double checked oil and everything was fine. I'd like to think it was the weather. 

^^^ ? What was the Ambient temperatures at when you were getting 7 mpg more, and how many miles to the gallon do you usually get?

Got my 1.4 TSI pre reg with couple of hundred miles on clock at end of last December, economy did improve when the weather warmed up but by this time had done a few thousand miles which may have helped.

 

For some any comparisons will be further complicated by summer v winter tyres.

 

Should be putting my winters on soon.

 

 

What is really hard to believe is that anyone doing a long trip during the day with the ambient temp at maybe 18*oC would get say 47 mpg and if continuing the trip 

at night and the temperature was down to 9*oC and the economy drops to 40mpg.

Usually those cooler temps give more efficient running, as when in warmer weather cooling oil requires energy. 

Radiator and maybe cooling fans to get the oil down, and keep it down.

3 hours ago, Headinawayoffski said:

^^^ ? What was the Ambient temperatures at when you were getting 7 mpg more, and how many miles to the gallon do you usually get?

 

on the same 35 min journey i was getting 60mpg easily (city driving). Today there was no traffic but it was around 10/11 degrees Celsius outside all the way. I averaged 52 mpg this time and on the instant display i can see that my engine was working harder than before. 

Edited 30 October, 20178 yr by Bertie90

If you have filled up in the past days then maybe your engine is not happy on the Winter Spec Diesel if that was in the filling station tanks.

10 or 11 degrees C is hardly cold weather, and your usual 60 mpg city driving is pretty wonderful.

 

You had The Fix imposed on your car as well, best keep an eye on your higher fuel consumption as VW Group gave you a guarantee that would not be happening after the new Engine Management was applied and the plastic hardware fitted.

Edited 30 October, 20178 yr by Headinawayoffski

My experience is that colder air temperatures do have an adverse effect on consumption for both diesel and petrol.

This is noted with my previous 1..9pd and current 1.4tsi Octavia.

The context is: on the same tank of fuel with the outward journey (100 - 200 km) undertaken in near 20 deg C temperature and the return journey at around 5 deg C. at night.

Conducted in our (Adelaide) winter in high pressure condition so no wind and clear sky, flat open roads and very low traffic; no air-conditioner.

Fully warmed engine and there would seem to be a 0.2 to 0.3L/100 penalty. Only obvious difference being headlights instead of DLRs'.

 

I'd even argue there are further economy benefits in higher ambient temperatures of around 40 deg C but they are disguised by running the air-con although the consumption penalty of running the air-con on a run seemed remarkably small even at those high temperatures (particularly with the diesel).

 

Whereas higher density cold air does offer improved power outputs it does not seem to translate to better fuel efficiency  and the high density cold air does increase air resistance at speed.

 

Different ball game with short urban journeys from cold or very cold starts, and different again in Nordic conditions with engine heaters fitted and running

 

Edited 31 October, 20178 yr by Gerrycan

There are many many factors that go into engine mapping vs ambient conditions. The official tests are done at 23 deg (for Euro 6c there is now a 14 deg test as well which goes into the mix) however the official tests are still far from perfect (part my day job is to be involved in the official tests for certain manufacturers).

 

as the ambient air reduces the fuelling is altered and increased to help with cold starts, warm up plus EGR rates are reduced to help with condensation in the EGR system etc... plus as it’s generally winter you will have the heaters on, so taking heat from the engine meaning longer warm up times, plus electrical energy used to power the heater fans, head lights, rear screen heater, and the battery discharges more over night, when starting (colder oil, slower to start due to harder to burn the fuel... ) which all depletes the battery so the alternator has to work harder to charge it back up.. this uses extra fuel and a surprising amount.

 

add in winter fuel as well, and it all stacks up. In summer my first mile of my trip can be 35-40mpg average, in winter that can be as low as 25mpg, so to get back to the same average by the time I reach work 35 miles away I have some how be more efficient than I am in summer, which isn’t easy..

Do drivers of identical vehicles that drive very similar and do similar journeys but one does it in the colder north and the other near the warmer south coast get so different fuel economy. Better fuel consumption in the South or Midlands to the north of England or North of Scotland!

Maybe Fuelly comparisons needed, or fleet operators would need to give the real world experience.

 

 

The Real World Testing is now started in the EU, thing is, empty cars, testers choose locations, time of year etc, but they are building and testing cars for the EU. (Empty that is other than Test Equipment & Driver, so really like a Rep Mobile / commercial travellers journey.)

Figures never given for a full loaded car to Revenue Weight, or maybe one towing a caravan... Like 'Real World users us vehicles as well as solo drivers'..

 

Edited 31 October, 20178 yr by Headinawayoffski

As Gerrycan pointed out, I think the ambient & road conditions have a significant impact, perhaps more so than any effect on the engine.

I have a 4.5km stretch of steady downhill on my way home from work.

In hot summer conditions starting at the top at 120kph & coasting in 6th gear the car will slowly accelerate to around 135kph & often I have to brake to reduce the speed.

On colder days, the car will maintain 120kph without any intervention.

On wet days the car with decelerate down the hill perhaps losing 10kph by the time I reach the bottom.

Without any changes to the engine or fuel, you can see the effect of air pressure & road friction/drag on the load on the engine.

 

This is 20minutes into my journey so the engine is fully warm by this point.

Diesels always get less MPG as the temperatures drop but also a more power. This is because the air is more dense at lower temperature which is measured by the MAF before it is compressed further by the turbo. Fuel is then injected in to match the air density and throttle position as calculated by the ECU. You'll notice the opposite in hot weather with the MPG rising but the power is down too. 

Add the more dense air to travel through, tyres being colder for longer and the engine itself taking more time to reach peak operating temperature and there you have your answers.

^^^ ?

If you have your summer tyres (ECO tyres) still on as the road surface gets cooler and the friction / grip is less does that assist the Economy?

http://trafficscotland.org/weatherstations 

*Many drivers in Scotland today will be driving in day time & night time temps 10*oC higher than 24-48 hours previously will it improve there MPG, 

or will the foggy conditions cause more traffic delays than yesterday?*

?

Do those winter tyres you fit with better grip in the cold but maybe narrower and a bit taller total diameter help in better economy or hinder it?

?

Does slowing down because of colder weather / road surfaces etc and longer braking distances assist in better fuel economy?

 

Swings and roundabouts

 

PS

Turbo / Twincharged Petrol Engines and Turbo Diesels can love 'Slightly Moist cool weather', yet rainy days can have so much affect on increasing fuel used especially on small capacity & power output vehicles, as can headwinds, yet sidewinds, tail winds are wonderful though..

Edited 31 October, 20178 yr by Headinawayoffski

Summer tyres in cold weather are less efficient grip wise and regardless of traction control you will still lose some traction which is wasted energy and therefore fuel. Winter tyres can also be the same as they can be too grippy so more energy used to overcome rolling resistance even with narrower tyres.

There the other factors too brought on by winter driving including heated screens and seats that all require electrical power which means the alternator needs to top up the battery which creates more work for the engine to do. Also take into account how much more traffic there is on the roads as it gets colder too with much more stopping and starting.  

Like most things a car requires more energy to operate in colder weather.