Hi

My diesel vrs has suddenly dropped the fuel economy, I normally get an average of 55-60mpg when I do a 200 mile trip to Cornwall. Done this trip a few times before, same speeds and driving style, this time I am down to 40-45 mpg.

Always run a Shell fuel.

Not sure if it's down on power a little bit as well.

Any ideas

Have you checked tyre pressures? I know you'll probably have the pressure loss system but just give them a check. It's amazing what just a tiny drop in PSI will do to your economy.

Rain and cold weather also kills economy on my car.

+1 for tyre pressures, they make a big difference.

Also driving into a headwind at motorway speeds can have a big effect on fuel ecomony.

 

mid-40s is not a terrible mpg for the vRS (some people have never managed to see this) and your normal consumption of 55-60mpg is really at the frugal end.

I would give it a while, keep an eye on it & see if it comes back to what you'd expect.

 

It could be just a case of bad timing - unfavourable weather conditions + regeneration during your trip etc

This week the Fuel Depots have started distributing Summer Spec Diesel & Petrol to Filling stations as the end of March in the UK is considered to be the end of the need for Winter Spec Fuel.

 

Could this be the reason for a change in your economy.

?

When did you last fill up your tank?

This week the Fuel Depots have started distributing Summer Spec Diesel & Petrol to Filling stations as the end of March in the UK is considered to be the end of the need for Winter Spec Fuel.

 

Could this be the reason for a change in your economy.

?

When did you last fill up your tank?

 

Yes, good point..

This week the Fuel Depots have started distributing Summer Spec Diesel & Petrol to Filling stations as the end of March in the UK is considered to be the end of the need for Winter Spec Fuel.

 

 

Interesting, i always think the fuel in Devon and Cornwall doesn't seem to be as good as that from Bristol area upwards - i didn't know if it is 'shipped' differently to plymouth or something.

 

 

Hi

My diesel vrs has suddenly dropped the fuel economy, I normally get an average of 55-60mpg when I do a 200 mile trip to Cornwall. Done this trip a few times before, same speeds and driving style, this time I am down to 40-45 mpg.

 

 

 

If it was this weekend, was it particularly windy on your way down (storm Katie and all that) - i notice bad mpg if the prevailing south westerly are blowing when heading home from up country.

Hi,

Tyre pressures were checked before journey.

It was this week and must have been driving in to the wind not that you noticed in the car. Came back yesterday afternoon after filling up with crap supermarket fuel and having to deal with a few cars that thought they were going to out accelerate me up the hills on the A39, anyway the car was up to 55 mpg by the time I got home.

I was wondering when they stopped with winter fuel but hadn't been affecting the car much not like on the Yeti. Went to Edingburgh and back a few weeks ago 600 mile round trip and averaged 58mpg. But the fuel economy dropped after that trip. Maybe picked up so poor fuel there.

I have been surprised what fuel economy I have got out of the VRS but I am also a National Observer for the IAM which does make a difference of how you drive a vehicle and use the power.

Thanks for the replies.

This week the Fuel Depots have started distributing Summer Spec Diesel & Petrol to Filling stations as the end of March in the UK is considered to be the end of the need for Winter Spec Fuel.

 

Could this be the reason for a change in your economy.

?

When did you last fill up your tank?

Shouldn't it go up not down when you move from winter to summer?

Truth be told you have no idea what you are sold other than it meets the minimum standard, and as for the drop in economy with winter spec I have neVer experienced that when you are not experiencing cold winters, and you are not using more fuel because of extended warm up times, and I mean with dirty diesels. Petrols love cold air and winter spec petrol

Truth be told you have no idea what you are sold other than it meets the minimum standard, and as for the drop in economy with winter spec I have neVer experienced that when you are not experiencing cold winters, and you are not using more fuel because of extended warm up times, and I mean with dirty diesels. Petrols love cold air and winter spec petrol

Winter fuels are not provided in my region, but why would petrol specs vary between seasons?

Petrol engines may love cold air for power but economy is worse in those same cold conditions and economy is the topic.

The formulation is made less hygroscopic in winter for Europe and this incudes the UK, ie absorbed less H20. If in doubt check it out. It is not a Internet myth. . It is also less volatile because it can be. Google winter grade gasoline and see what is said in the US of A on cheaper and more pollution.

Edited 1 April, 201610 yr by GoneOffSKi

Economy is worse with defrosting. Lights and heater etc on longer. Then balance travelling slower, less grip on the road so less traction, cool air and an efficient running engine, which really is why many engines now run intercooler. So swings and round a bouts.

Edited 1 April, 201610 yr by GoneOffSKi

Well yes all of that, but my experience with a fully warmed engine, on the same stretch of very flat straight road, at identical speed, zero wind and on the same tank of fuel is that I will get average 5.7L/100 at 110 kph (GPS speed) at around 20 degrees centigrade and 6.0L/100 at around 10 degrees centigrade.

 

I have repeated the experiment many times.

Higher temperatures offer potentially better consumption again but then there is the need for aircon. At 35 to 40 degrees and use of aircon consumption is 5.9L/100

I get worse still at night with low single figures temperatures possible but then headlight use is a factor.

 

In winter sometimes we get a frost but as I live near the coast that is infrequent, more common inland.

My experience is of driving around 37 Scottish Winters and Summers and paying attention to Mpg,s and driving Keepers over several years, and then also Dynoing cars and bikes and using in motorsport , so leaded petrol, Unleaded, and Shell destroying engine formulated in late 80's, so just the experiences of running mostly petrol/benzene, but occasionally Derv, and paying for the fuels.. It is not rocket science, just motoring.

Edited 1 April, 201610 yr by GoneOffSKi

I'm just relating my experience with just one parameter and old school physics where I was taught that warmer air is less dense than cool air.

Warmer less dense air would require less fuel and also lower wind resistance.

Science is great, real world can be as well, an efficient running engine getting cold and denser air (oxygen) might require more fuel and give more performance, 

or just be running efficiently as modern engines can, mapping dealing with it and you can keep your speed for the road temperatures and use no additional petrol, 

or diesel if that is what you run.  No A/C on, and it can be cold and clear and roads dry and no lights required.

Also engines that run above the efficient operating temps for the oil require cooling, cooling uses energy.

 

In the UK many buyers of petrol (Gasoline) have little idea of what they are receiving, they might know the brand and the Minimum Octane, 

and 95, 97 or 99 ron, and Winter Grade Late October til March, then some years it may be for longer.

http://platts.com/latest-news/oil/london/uk-still-buying-winter-gasoline-as-european-refiners-8114744

Edited 2 April, 201610 yr by GoneOffSKi

For some reason my iphone refuses to open your link to platts.com?

Not your phone,

it did work when posted.  maybe Briskoda members caused it to crash.

It was back in 2012 and on Winter Grade Petrol still being bought later than usual for the UK.

 

Parts of the US have had an issue very recently with a shortage of Winter Grade fuel because of the very low temps.

The winter derv contains additives and shorter chain hydrocarbons to prevent waxing.

Hence less energy per litre of fuel and so less mpg.

 

Of course filling up when it's cold also means a greater weight of fuel per litre, so it's a trade off.

Either way, I always found the MPG went up a little bit in the spring as they switched the fuel, but before it got too warm.

 

Still as you say, it's not really a highly predictable thing, because everyone can use a different package if they like, as long as it meets spec.