I recently noticed the fuel consumption of my 1.6 diesel Fabia wasn't very good. Typically, this time of year, I see 50 to 55 mpg. But a couple of weeks ago in fairly chilly weather, it was under 50. Last Friday I did a 25 mile journey, a mixture of country road, dual carriageway and a couple of miles of town driving, and it was down to 44. The return journey from cold only gave 33mpg!

I was worried something in the engine or exhaust was broken or breaking. So I didn't use the car over the weekend. On Monday I called my nearest Skoda dealer asking for their advice. The car is 2.5 years old and has done 22,400 miles. So it is still under warrantee. The garage - Walkers in Kings Lynn - booked it in for an inspection this afternoon.

On the journey to Kings lynn, the car had averaged 31 mpg after 10 miles. But then it picked up a bit to 37 after a total of 27 miles. The garage checked the car and could find no problems. It started easily, ran smoothly and accelerated well. The idling was smooth with no strange noises.

Sorry about the long build-up.

I keep a log book of fuel purchases. It shows that recently I have been using standard Esso diesel. But the last refill was with Shell diesel. Both brands have introduced new improved fuels recently. Esso claims better fuel consumption and Shell more performance. I had used about one third of the tank of Shell diesel when the car returned 33mpg.so the problem wasn't immediate after refilling.

When I bought the car, 18 months ago, I tried various brands and grades of diesel and noticed that changing from normal to super diesel produced worse fuel consumption by 5-8mpg. I had read somewhere that modern engines 'tune' themselves to get the best performance/fuel consumption from whatever fuel they are fed. So changing brand or grade might lead to a temporary increase. However, I wasn't prepared for a drop from an expected 50 - 55 mpg to a figure in the low 30's which is what I now suspect has happened.

So I will stick to one brand and grade of diesel in future as much as I can. This isn't a rant about one brand being better than another. Just don't change if you can avoid it.

If you have seen similar problems with fuel consumption, I would be interested to hear about them and how they were resolved.

I have to add that the Skoda dealership were very helpful, made no complaints about my possibly unnecessary concerns and no charge either!

Slow Bloke

thing like regen of DPF have a big impact on mpg, as does tyre pressures and roof boxes, less so but still impact are weight carried in boot, number of passengers

I have kept a careful log of fuel as well only big different I have seen is Tesco diesel (my car don't like that stuff at all), all the rest are not to far apart, my car seems to like esso best then bp,shell with morrisons/asda similar

I have 18k / 11 months of data so far tracking fuel brand, mpg, trip meter mpg against calculated mpg and cost per mile

but until I get at least 10 tankfuls on each brand I don't think I have enough data for a definitive answer

Can't say I've ever noticed such dramatic change between fuels when I've owned diesel cars

shell gives me by far the best diesel consumption

Mostly Morrison's fuel sometimes Asda.

Getting a steady 54mpg. Only 2500 miles so far.

Spending more time in Dealers than on the road.

I use whatever I happen to be near, but usuall the local Suzuki garage (no idea on fuel brand), as it is en route on my twice daily trip to the nursery.

My economy has edged up in the last few weeks, from just under 50mpg to nearly 55mpg.

I'm putting it down to it being fully run in (12500 miles), not on winter fuel in the last few weeks (no proof, but guess work), slightly warmer weather, so quicker to warm up and "knowing" the drive like the back of my hand - so can coast at all the right points and blast it conservatively, without smashing economy.

A very interesting article in CAR magazine this month - in the Insider section. Audi have been successfully sued by an owner, for claiming an unachievable 68mpg. It went into detail on the EU test cycle - 6.9 miles, never really running at "motorway" speed and lasting about ten minutes. It said that new-generation Turbodiesels are the worst affected and display the biggest gap - in the EU test, they run off boost for most of the time, but in "the real world", they never run like this...

in my experience I would say the official figures are nearly achievable depending on circumstances but you should be able to achieve the urban figure without much issue tanks on tank

from my data the branded fuels are showing a 2-3mpg advantage over supermarket at 60-65mpg so less than 5%, this could be due to difference in conditions, load or driving style at the time, but it is seeming to be consistent

my original Octavia 1.9pd 90 I achieved the extra urban tank on tank for some time but I did a regular long run at steady speeds

my roomster 1.9pd 105 I used to achieve the combine-urban figures depending how heavy my right foot was on the m40

my GLII I am just under the urban figures tank on tank, but regularly seem 70+ mpg(near the combined figure) on individual runs and if I drive carefully on longer motorway runs I get into mid to high 80'smpg, last week on a run back from Birmingham to kent (190 miles) I saw 89.3mpg average over whole journey, less than 5mpg of the official extra urban figures, was in no rush so drove back at 56-60mph and had a clear run

I think the way I look at the "official" mpg figures is you should be able to achieve the urban in reasonable day to day driving, the combined should be achievable on longer runs of 50+ miles and you should be able to get close to extra urban on a rare occasion if you really try and drive like a granddad

if you doubt the official figures look on somewhere like fuelly to see what real people are actually getting for the same make / model you are considering / running

Edited 22 May, 201313 yr by bluecar1

I know from my car, which is a petrol consumer, that when I fill her up with a specific brand of 95RON supplier I can see up to 1140 Km of autonomy, while using another 95RON petrol, it never comes above 920 Km of autonomy.

We all know that these figures are due to our way of driving. Yes it is so, but using the first fuel I can make about 1.000 (980 to 1010) real Km, but when on second fuel brand I make about 850 real Km ( + - 50 ).

And because I am a very strange kind of person I keep up refueling from standard fuel stations (when possible) and when in trip only from the same two brands, because last 15 years I 've never had any fuel related problems, except the difference of autonomy.

Sorry for not naming the brands, but I live in Greece so we have different fuel brands, beyond Shell and BP which are common but I do not use their fuels something that makes me unable to give you a complete report.

Edited 22 May, 201313 yr by stratosg

I have recorded my fuel use geekishly for maybe 25 years. Over the last 15yrs I have recorded the brand used. That is over 3 petrol and 2 diesel cars. In all that time I have never seen any significant difference (ie more than 1 or 2 mpg over a long term average) in fuel consumption between brands or between "super" fuels vs "standard" fuels. With my current car the best mpg has been given by Morrisons or BP and the worst (2mpg behind) is Shell.

I have had several instances where single tankfuls have given unexpectedly low consumption that have taken a couple of fills to recover from. With diesels you definitely get the drop in mpg of 3-5mpg from summer to winter grade.

With Winter Diesel, it is usually sold in the Winter Months.

& Fuel economy will be dropping with all the factors of Winter, (Late Oct-March/April)

Longer Warming up, running engines defrosting, Lights, Heater, Rear Screen on etc.

The way to tell if you get Worst Economy with Winter Fuel/Diesel, might be to Buy some when on sale & Store and use it in the summer months.

You might actually find it gives better MPG in warm weather.

george

With Winter Diesel, it is usually sold in the Winter Months.

& Fuel economy will be dropping with all the factors of Winter, (Late Oct-March/April)

Longer Warming up, running engines defrosting, Lights, Heater, Rear Screen on etc.

The way to tell if you get Worst Economy with Winter Fuel/Diesel, might be to Buy some when on sale & Store and use it in the summer months.

You might actually find it gives better MPG in warm weather.

george

Maybe true but mpg drops off a steeper cliff than the ambient temperature!

When i drove diesels mine improved in winter.

Colder Air more oxygen and better running engine,

Low Ground Temperture/less grip/traction on the road, so lower road speeds driven.

Equalled better MPG and no Waxing of Diesel when the weather got properly cold..

& none worse on warm days which is the Majority of the 4/5 month period of Winter Fuel Supplied.

george

Fuel consumption in my MKI Fab vRS nosedived in winter - however, a lot of that would've been down to my short journeys - usually about eight / ten miles - never got a chance to warm up properly.

Since 2005 I've only ever used Shell V-Power (petrol and diesel) unless I haven't had enough fuel to get to a Shell station - pulled into Johnstone Bridge services on the M74 last month - all the Ultimate pumps were tied up - I was raging as its the first time I've had to put 'pauper petrol' in the vRS - only enough to get me home mind (although I didn't actually notice any difference... ).

Thanks for your comments.

My concern was the sudden rise in fuel consumption. The car normally gives 50 to 55mpg this time of year. I was afraid there might be a serious mechanical problem. As this was not the case, I thought I would warn other owners of the strange behaviour.

I

Thanks for your comments.

My concern was the sudden rise in fuel consumption. The car normally gives 50 to 55mpg this time of year. I was afraid there might be a serious mechanical problem. As this was not the case, I thought I would warn other owners of the strange behaviour.

Your drop in mpg was certainly dramatic. My experience with the 1.9 PD has been quite different in that premium diesel always improves mpg. Shell V-Power is the best. Even when I really cane the engine with this stuff in the tank it stays above 50 mpg (maxidot reading rather than brim calculations though) in extra urban settings, and if I'm on A roads and motorways, I can achieve early 60s if I stick to speed limits. The 1.9 TDi is surely one of the best engines VW has produced (completely unbiased view of course ;-)

While I too keep a log of my fuelings, albeit without noting the brand, I have never experienced any difference in mpg when switching brands. What I have noticed is that even slight headwind and/or light rain will significantly increase or decrease my mpg. Besides, IMHO, a 25 mile journey really isn't long enough for settling the mpg at a steady rate; it only takes one or two heavy accelarations (or the lack of such), especially when starting to drive with a cold engine, to change the figures completely.

Here (hopefully!) is real data from my 1.9TDi PD 105PS - but in an Octavia. This is fill data (not trip computer) data gathered over 36,000 miles. You really can't judge fuel differences over a single trip or a single tank. My 8 mile commute to work in the current car varies between 28 and 42mpg. There is also the unconscious skewing of the results by driving that little bit more gently because you want to see if V-Power really is better. That is why blind tests are the only way.

TDi Fuel Consumption.pdf

Nice stats, eccleshill!

I calculate the standard error (margin of error) of your mean MPG values for premium and standard diesel as 1.2 and 0.8 MPG, respectively (assuming your standard deviation per tank is the same as mine: 6MPG).

Conclusion of my analysis: No significant difference in MPG between premium and standard diesel.

In fact, there is no statistically significant difference between any of the fuels.

Edited 5 June, 201313 yr by Igloo Vindaloo

Nice stats, eccleshill!

I calculate the standard error (margin of error) of your mean MPG values for premium and standard diesel as 1.2 and 0.8 MPG, respectively (assuming your standard deviation per tank is the same as mine: 6MPG).

Conclusion of my analysis: No significant difference in MPG between premium and standard diesel.

In fact, there is no statistically significant difference between any of the fuels.

From the point of view of MPG - I agree with your analysis. Though I am intrigued by BP having the best and the worst!

Did I notice any difference in driving? - Maybe!. With BP Ultimate the engine seemed to be quieter. Maybe the placebo effect 'cos I'd just spent £4-5 extra filling the tank!

My reason for persisting with the premium fuel was the cleaner burning aspect - maybe its intermittent use (generally in 3-4 fill "campaigns") helped to keep the engine clean and thereby improved mpg across the piece.

My reason for persisting with the premium fuel was the cleaner burning aspect - maybe its intermittent use (generally in 3-4 fill "campaigns") helped to keep the engine clean and thereby improved mpg across the piece.

These sort of things are very difficult to test - without identical cars doing identical journeys at identical times.

Sometimes I think that is why they claim the benefits come from extended use - because they know it cannot be tested!