3 minutes ago, SC03OTT said:

Hmm. I'd be surprised if your oil is up to full operating temp within 2 miles. 

 

Im agreeing with the above though, which was the basis for my initial questions. 

 

I will check tomorrow both - water and oil temp.

No way is the oil at around 90*oC actually or even indicated by 2 or 3 miles, even if the Coolant has reached an indicated 90*oC.

Even if starting from cold with an ambient temp in the mid to high 20's.

Would low oil/water temperature have so huge effect on fuel efficiency? How much efficiency is killed driven with air con on?

Looking at your driving pattern - I would say that 38mpg is ok,most diesels would struggle to exceed 60 mpg as a true average,I have driven diesels for 30+ years.

My fabia 1.9tdi probably takes 10 miles or so to get up to 50mpg avg (on dash display),by 20 miles it may be up to 60mpg indicated,but I would never claim any more than 55-57mpg as a genuine avg figure.

As long as I get the expected range from a tankfull I only do a mental calculation of mpg from miles driven (on the odometer) and the fuel required to fill tank. 

2 minutes ago, Robertino said:

Would low oil/water temperature have so huge effect on fuel efficiency? How much efficiency is killed driven with air con on?

Yes - if you look at your mpg figure with a cold engine it is probably down somewhere in the 20's but as the engine warms up the mpg figure will start to climb.

There is not a low Coolant Temperature, engines / vehicles are designed to get the Coolant up to temp and then the oil up to temp, 

the oil is not at an efficient temp quickly in a diesel.

 

As to A/C, there is a minimal affect on economy, and as it is if comfort cost a few pence a journey who cares.

Edited 11 July, 20178 yr by Awayoffski

5 minutes ago, Robertino said:

 How much efficiency is killed driven with air con on?

Probably not too bad at a decent cruising speed but I would guess that air con is probably worse for mpg at low rpm's/below optimum power band.

If it is a scorcher and the car feels like a green house or it is steamy and the windows are fogging do you really care about dropping 2 mpg if it was that much.

If you do would you not be as well using public transport?

This is my recent driving data.

 

 

 

How much motorway/city driving? Amazing figures!

The air-con should always be used if the conditions warrant it, but as I said the official tests do not include their use.

My Octavia mk3 1.4tsi has a 'conveniences' display that shows the affect the air-conditioner use is having on consumption. I'd be surprised if it not standard on all mk3. On a hot day it is usually about 0.5l/hour which is not much but the equivalent consumption of my engine at tickover. Logically that constant circa 0.5l consumption will have a more marked effect at lower speeds than at higher speeds.

Unfortunately manufacturers try to hide the normal dpf regen requirement so you will not get an indication until things get quite seriously wrong. A longer and higher speed run every couple of weeks should be enough to keep it happy. There is a pinned thread on the subject.

 

The other thing is economy driving technique does not usually require driving like your Nan but driving at normal speeds with greater traffic anticipation to avoid unnecessary braking. If you have to slow then use engine braking to achieve it and get that rolling distance for free. Allow a little more distance from the car in front who has not done the same and whose brakes lights are flickering incessantly as they go back and forth from throttle to brake.

 

I can get better consumption returns in our urban environment (60+mpg) than I do on the open road (50+mpg) but only if the distance is about 10km or more. Understand that my mk3 is a petrol and my previous mk2 1.9pd did not have a DPF.

Edited 11 July, 20178 yr by Gerrycan

You can't compare in between different drivers and routes how much fuel car should consume.

 

My wife drives our second Octavia, TDI 150HP, also short distance 5km to work, no congestion. With a few traffic lights and with engine that never reaches working temperatures she gets 33-35mpg for example. This car is simply not made for such a work conditions, as I was getting in Greece with that car 70+ (driving really gently and defensive to be honest).

3 hours ago, Robertino said:

Would low oil/water temperature have so huge effect on fuel efficiency? How much efficiency is killed driven with air con on?

 

Of course, a cold engine will use 2 or 3 times more fuel when it is first started than when it is up to temperature.

You have first the increased engine friction when the metal & oïl are cold.

Plus there are lots of stratégies designed to increase quickly the temperature of the exhaust, catalyst & coolant/oïl etc as this is very important for emissions & passing the EU tests.

 

Driving my car here from cold yesterday (>30°C ambient!!) & the instantaneous fuel economy for the first few kms is around 10L/100km.

When I reach the highway and the engine is up to temperature my average economy is between 4.5-5L/100km. (~50mpg)

 

Air condition has a much smaller effect on fuel economy & is pretty efficient when the vehicle is moving & there is a good airflow through the engine bay.

If the outside temperature is hot or the vehicle is not moving so fast the power draw will be increased but probably only a couple of mpg as others have stated.

I checked this morning using dot matrix display:

Total journey 4.5 miles

Oil temperature showed up first time at 51 degrees, after driving 2.6 miles.

At the end of my journey, oil temperature was 74 degrees, water 90.

Edited 12 July, 20178 yr by Robertino

2 minutes ago, Robertino said:

I checked this morning using dot matrix display:

Total journey 4.5 miles

Oil temperature showed up first time at 51 degrees, after driving 2.6 miles.

At the end of my journey, oil temperature was 74 degrees, water 90.

 

Using a diesel engine for such short journeys is the problem with your fuel economy. As you can see from your readings the engine has barely warmed up and diesels are big heavy lumps to get up to ideal operating temperature. Running air con etc will just compound the problem. If you're journey is a lot of stop/start traffic that will kill the economy too, seeing as you're in London I'd imagine this is the case. A small petrol engine would have been better suited. At a guess I'd say your average speed is well down around 15-18mph. Come winter you see a further decrease in economy.  

Why did you buy a diesel?  Doesn't seem to be best suited to the mileage, type of driving you do IMO.  Based on what you've already said about types of journey, MPG and such I would be more concerned about your DPF, EGR valve, etc. 

I bought it because of promised amazing mpg. EGR can be disconnected - it does enough harm - hot air and all that black stuff going into engine. DPF - I`m not rich enough to replace it at 1.5k, will have to try those special cleaning products.

On 10/07/2017 at 19:07, Robertino said:

I have driven on motorway and average goes up to 59 (still miles out from 80 listed). On motorway I can get it to max current 68 mpg, driving 60mph, fiddling with pedal like acrobat waling on rope - hard to keep constant pressure on a

ccelerator - I miss cruise control so badly.

 

 

I regularly get 70+mpg (sometimes 80+) on my 1.6tdi manual (38miles mostly motorways and mostly 50mph average) - shorter journeys will be mid to low 40s.  I don't bother with the Eco setting as it doesn't do much with a non DSG car - so mine's set to sport - doesn't make a jot of difference to the mpg - I just prefer the steering weight and throttle response. 

 

The best way to save fuel is not to accelerate hard and more importantly brake hard.

 

 

Edited 12 July, 20178 yr by io1901

2 hours ago, io1901 said:

 

I regularly get 70+mpg (sometimes 80+) on my 1.6tdi manual (38miles mostly motorways and mostly 50mph average) - shorter journeys will be mid to low 40s.  I don't bother with the Eco setting as it doesn't do much with a non DSG car - so mine's set to sport - doesn't make a jot of difference to the mpg - I just prefer the steering weight and throttle response. 

 

The best way to save fuel is not to accelerate hard and more importantly brake hard.

 

 

Do you even feel a difference in throttle respons in sport vs normal? i feel the weight of the steering but i can't say i notice any better throttle respons. i have a manual too.

anyway, got 72mpg this morning on a 30km (18miles ?) trip, driving like an old lady...

Engine doesn't have chance to warm up enough. With my MK2 diesel VRS, it took closer to 20 mins to properly reach temp (oil min 80c) and never got warm enough during winter commuting. I heard plenty of DPF regens and economy was pretty poor too. Longer runs were far more economical.

46 minutes ago, bytterga said:

Do you even feel a difference in throttle respons in sport vs normal? i feel the weight of the steering but i can't say i notice any better throttle respons. i have a manual too.

anyway, got 72mpg this morning on a 30km (18miles ?) trip, driving like an old lady...

 

I think throttle response was the wrong expression - you don't have to press the pedal as much to get the same acceleration. So it doesn't go any faster but you don't seem to have to push the pedal as much to get there. 

50 minutes ago, bytterga said:

driving like an old lady...

 

I always drive like an old lady

Went on long journey today.

 

From Heathrow to Northampton, 60 mph, average consumption by Maxidot 78 mpg 

From Northampton to Heathrow, 65 mph, average consumption by Maxidot 72 mpg 

 

Woow! This is what I was expecting from this car and so happy.

Edited 15 July, 20178 yr by Robertino

Robertino, what you've been experiencing is completely normal and I wouldn't get lost in oil temperatures or making tweaks to the car's tech somehow.

 

As has been mentioned by others, you should take most 'official' comsumption figures with a pinch of salt. I operate on the basis that the only figure that's likely to be anywhere near what you'll achieve as a real-world average is the urban consumption number. The combined figure may as well have been plucked from thin air for all the technical logic and scientific accuracy behind it.

 

Seems to me that on that basis you've actually been doing pretty well. No, it's not the mega-number those daft official figures might lead you to believe, but you're not doing anything wrong and 38mpg for a five-mile hop is very respectable.

 

One point I would make is that your daily mileage seems low, and the motorway jaunts you mention above a rarity. On that basis, you might be better going for a petrol engine next time. Will cost you less to buy and you might be pleasantly surprised by the economy.

Maybe it also helps that I filled up with Shell V power. In my previous tank I still had some unknown fuel since I bought the car. I never buy cheap fuel, only Shell V power.