After filling up with V-Power diesel in Germany i took the car on a dyno run to see the difference. Before it did about 167bhp chipped with 371nm.

After: 181bhp with 387nm. Pretty impressive.

That's interesting, despite all the doubters I've always felt that the ol' snake oil really did make a difference to a CR engine. Couple of questions though, was that on the same dyno? & was that just the one tank of fuel you ran through it?

Same dyno, one tank.

PD engine seems to like V-Power a lot better for some reason. CR engine doesn't have such a high increase i think.

Edited 23 February, 201313 yr by Cown

I know v-power does make some difference but I'd be surprised if it made that much of a difference. Trying to rule out any other factors can be difficult. Time of year, altitude, air-temp etc etc

I know v-power does make some difference but I'd be surprised if it made that much of a difference. Trying to rule out any other factors can be difficult. Time of year, altitude, air-temp etc etc

Yeah it seems amazing... Not sure if there are other factors to calculate with. Temp yesterday, when testing, was -1 celcius. Earlier test which showed 167bhp, was with +13 celcius. Same altitude though, Denmark is very flat... hehe

Odd thing is, diesel engines lose performance in winter months. Maybe the lower air temp helped a little though ... like nature's own intercooler.

Whatever other factors are, good quality diesel does increase peak performance somewhat, ie either max torque or max power. Usually for the simplest reasons of them all, higher cetane rating (ignitability), faster burn speed, and more complete burn under limited air supply.

In winter, the difference between premium vs standard fuel can also be more pronounced because of different energy content.

To winterize "standard" fuel, more thinner is added (there are more waxes to dissolve) and calorific value is lowered more, resulting in lower power/torque under constant fuelling. Premium fuels typically have more uniform composition which results in less winterizer needed.

Though I would not put it to V-Power diesel specifically, I hardly ever use it. But I do notice change in throttle response above 3500rpm/6th from my 2.5TDI depending on where I fill up in Europe. E.g. from 120+ trips "perception average", French and UK fuel is about the same for high engine loads on average, Danish and Swedish is actually worse, Dutch and German fuel is usually very good, and Austrian and Polish tend to vary, sometimes as good as UK, sometimes much better. I fill up with regular diesel in every country mentioned.

You are right (dieselV6) about quality of Danish fuel being total waterish. The fill up with V-Power from a German Shell station could've been the biggest difference resulting in the high increase of power... only a guess.

Observation from another Scandinavian is that the Shell V-power sold here in Norway is not influencing power, torque or economy in any amount I have managed to detect compared to the usual Shell diesel I normally tank.

But, last summer, going through Germany towing a trailer, so obviously keeping a relative constant speed on the Autobahn, I filled up at an Aral station with Aral Ultimate. The small rest I had on the tank were standard Norwegian Shell diesel, and the difference were beyond what I thought possible. The engine (the nightmare 2.0 PD) ran much more smooth, and the consumption sank 10 - 15%. I can't really say anything about power, but it felt better.

I also heard stories about truck drivers, talking about Russian diesel, where they could feel a real difference in power compared to Norwegian diesel, real Russian power!

A theory is that the bio-diesel they are blending in all diesel here in Norway, and perhaps also other places is not very good for the performance. Perhaps the bio-diesel mix is not containing the same energy amount, or is making the blend not so efficient in the combustion, lowering the performance? I think the diesel at the pumps here in Norway by law must contain at least 5% bio-diesel.

And yes, I can definitely measure a difference on the consumption during the winter compared to summer. My average winter consumption is approx 10% higher than in summer. In my area they are starting to sell "winter diesel" in September, normally guaranteed not to "wax" at temperatures down to -30 deg C. It's probably not just the diesel, as cold weather making all movements harder, winter tires with worse performance and snow on the roads probably also is contributing.

I can also confirm that after filling up with Aral Ultimate Diesel in Germany my 2.5 tdi felt more responsive, and it was more economical too, I hit nearly 40mpg despite being most of the time in the 3 figures on the speedo. It was, however, quite expensive indeed, but whether one can fully offset the mpg improvement/ drivability / power against price per litre not sure, but for driving enjoyment it was definitely worth it. Will be tempted by it again.

Let's not forget in this debate that specific countries have specific climatic and road surface characteristics that will bias country-specific-fuel-related fuel consumption statistics. For example, I always find in Hungary my fuel consumption is lowest despite doing the highest speeds - it's all very flat there and in the summer the temperature is regularly close to 40 degrees, so nice low air resistance contributes to fuel economy, and the road surface is smooth too. In the UK (on French diesel) my mpg is always worse than in France (on French diesel) for example as our road surfaces are rough as a bear's a**e.

I've got a shell garage near me, but the v-power is loads more expensive. I've bought some millers to see if that makes any difference, mainly to try and offset DPF issues, though that's more out of hope than basd on knowledge. Has anyone else tried millars vs v-power in their CR and if so what did they find as it's supposed to increase the ceatine rating by 4 (what that means in the real world from a practical point of view I've no idea!)

People say in warm weather the air resistance is lower and this is true. But the air density is also lower therefore less oxygen. In cold weather the air is obviously more dense but that obviously means more air resistance.

I've always wondered which is best or has the most affect.

I've put some V-Power into the Yeti today - first time I've ever used anything other than regular diesel. It was a bit disconcerting paying a pound more for three litres less than the last tankful (though prices have gone up 2p/litre in the last fortnight which doesn't help). Primarily I want to see if the economy is any better, so I need an extra 2mpg for the 8p/litre difference. Current long term average is 41mpg with the last half dozen fill-ups being around 42mpg.

Edited 27 February, 201313 yr by dbg400

I've got a shell garage near me, but the v-power is loads more expensive. I've bought some millers to see if that makes any difference, mainly to try and offset DPF issues, though that's more out of hope than basd on knowledge. Has anyone else tried millars vs v-power in their CR and if so what did they find as it's supposed to increase the ceatine rating by 4 (what that means in the real world from a practical point of view I've no idea!)

I use Millers. I never put much stock in thse things until a mechanic friend of mine said the manufacturers visited their dealership. They put the courtesy car on a dyno and ran a benchmark. Then they gave the staff a months supply of Millers, revisited a month later and re-dyno'd the same car. (Keep in mind nothing else was done to the vehicle in that time and the sales rep had no access to said vehicle). The dyno showed a 15bhp increase and the mpg figures improved by around 8%. I thought I'd buy some to see any difference. I'll be completely honest and say I do think there's a difference and my mpg figures may have risen a little ..... but as with anything like this, I reckon some of it may just be psychological. For instance, I can categorically state my car runs better when it's washed and waxed. I didn't run a dyno before/after.

People say in warm weather the air resistance is lower and this is true. But the air density is also lower therefore less oxygen. In cold weather the air is obviously more dense but that obviously means more air resistance.

I've always wondered which is best or has the most affect.

Yes, lower air resistance, so that's good.

In terms of lower oxygen concentration though.... the maps in the car run on the basis of airflow vs fuelling - the airflow maps have temperature correction factors, so the ECU knows the flow rate of "oxygen" into the engine and hence determines how much fuel it's prepared to inject to comply with emissions of smoke transiently (on smoke maps, as in when the boost is building up as you put your foot down). On a steady cruise, it will run off a boost and fuelling table, i.e. for a certain fuelling demand (from the throttle) it will match with the appropriate turbo boost. If you have a hot day, thin air is present, the compressor will just spin a bit faster to give the target boost pressure, it will then get intercooled and then digested by the engine. If the inlet air is of lower density, due to being hotter, the increased compressor speed will compensate for the lower ambient air density. It's in a way similar when you got the Alps, lower ambient pressure in that case (though temperature can be quite cold even in the summer) means that the engine will still target a target boost pressure (as per maps) and the compressor will just spin at a higher speed to deliver the target boost - so as the inlet pressure is lower than at sea level the boost ratio becomes higher - this automatic compensation for atmospheric conditions is one of the wonderful things about turbochargers. And this is exactly why we have altitude turbo protection maps - these lower the amount of boost a turbo is allowed to have at high altitude due to the fact that if you run at say 2.4 bar boost at sea level the TC wil do 150000 rpm while the same boost at 2000 meters will mean it will spin at 180000 rpm and might fail.

Sorry if I am confusing you, but basically I am saying that on a turbodiesel engine higher ambient temperature does not mean less oxygen is available for combustion. On an old naturally aspirated engine it could though (but these were "mapped" to have excess air to fuel ratio by default so some drop could be tolerated in the summer with no increase in emissions), but as all modern engines have MAF sensors, the amount of fuel going in will reduce too, so no smoke will be seen and no increase in fuel consumption either (you could only experience less power being available at WOT). Higher sump temperatures (lower friction) and lower aero loads always win in the summer, all things being equal.

Edited 27 February, 201313 yr by oh_superb

I've put some V-Power into the Yeti today - first time I've ever used anything other than regular diesel. It was a bit concerting paying a pound more for three litres less than the last tankful (though prices have gone up 2p/litre in the last fortnight which doesn't help). Primarily I want to see if the economy is any better, so I need an extra 2mpg for the 8p/litre difference. Current long term average is 41mpg with the last half dozen fill-ups being around 42mpg.

This is the annoying thing for me: all these modern cars have low CO2 numbers yet in real life they use as much fuel as my old V6 lump. My lifetime average is 39 mpg (last 35000 miles), not much less than the Yeti, and yet you probably pay £120 in road tax (or so) while I pay a "gas guzzler premium" at £270, and if it was post 06 plate it might even drop into the £400 bracket as over 225 g/km (I think).

Yes, lower air resistance, so that's good.

In terms of lower oxygen concentration though.... the maps in the car run on the basis of airflow vs fuelling - the airflow maps have temperature correction factors, so the ECU knows the flow rate of "oxygen" into the engine and hence determines how much fuel it's prepared to inject to comply with emissions of smoke transiently (on smoke maps, as in when the boost is building up as you put your foot down). On a steady cruise, it will run off a boost and fuelling table, i.e. for a certain fuelling demand (from the throttle) it will match with the appropriate turbo boost. If you have a hot day, thin air is present, the compressor will just spin a bit faster to give the target boost pressure, it will then get intercooled and then digested by the engine. If the inlet air is of lower density, due to being hotter, the increased compressor speed will compensate for the lower ambient air density. It's in a way similar when you got the Alps, lower ambient pressure in that case (though temperature can be quite cold even in the summer) means that the engine will still target a target boost pressure (as per maps) and the compressor will just spin at a higher speed to deliver the target boost - so as the inlet pressure is lower than at sea level the boost ratio becomes higher - this automatic compensation for atmospheric conditions is one of the wonderful things about turbochargers. And this is exactly why we have altitude turbo protection maps - these lower the amount of boost a turbo is allowed to have at high altitude due to the fact that if you run at say 2.4 bar boost at sea level the TC wil do 150000 rpm while the same boost at 2000 meters will mean it will spin at 180000 rpm and might fail.

Sorry if I am confusing you, but basically I am saying that on a turbodiesel engine higher ambient temperature does not mean less oxygen is available for combustion. On an old naturally aspirated engine it could though (but these were "mapped" to have excess air to fuel ratio by default so some drop could be tolerated in the summer with no increase in emissions), but as all modern engines have MAF sensors, the amount of fuel going in will reduce too, so no smoke will be seen and no increase in fuel consumption either (you could only experience less power being available at WOT). Higher sump temperatures (lower friction) and lower aero loads always win in the summer, all things being equal.

No you're not confusing me. You've cleared up something I've long pondered. Thanks! Clever little things these cars then lol.

But obviously a Supercharged engine wouldn't be able to compensate as it spins relative to engine speed, yes?

I used to have a supercharged, the noise was amazing!

Im on it right now and it feels better than usual fuel from tesco or sainsbury

No you're not confusing me. You've cleared up something I've long pondered. Thanks! Clever little things these cars then lol.

But obviously a Supercharged engine wouldn't be able to compensate as it spins relative to engine speed, yes?

I used to have a supercharged, the noise was amazing!

With a s/c engine, you are right, it's just a fixed volume ratio (Roots type blower assumed rather than centrifugal) so lower inlet pressure will mean lower output pressure.. it's just a fixed ratio of absolute pressure (not gauge). Yes, s/c is the way to go if you have deep pockets and don't mind short fuel tank autonomy...

With a s/c engine, you are right, it's just a fixed volume ratio (Roots type blower assumed rather than centrifugal) so lower inlet pressure will mean lower output pressure.. it's just a fixed ratio of absolute pressure (not gauge). Yes, s/c is the way to go if you have deep pockets and don't mind short fuel tank autonomy...

Lol I so mind. That's why I no longer have it. Was an awesome car though but struggled to get 25 MPG.

My Superb with Eco remap and 60+ mpg is just fine

Thanks for your time replying anyway!

Im on it right now and it feels better than usual fuel from tesco or sainsbury

Even regular Shell is better than Sainsbury's stuff. My car definitely runs better and delivers better mpg on branded stuff, particularly Shell. I have never tried V-power diesel. It's mostly GTL (gas to liquid) sourced, so literally no sulphur and high energy density and high cetane number, which reduces ignition delay and maximises engine work on the crank reduces smoke and exhaust temperatures and maximises fuel economy. It's all good stuff but expensive at that too. Tempted to try MIllers EcoMax cetane booster soon, many people claim 10% improvement in mpg.

Lol I so mind. That's why I no longer have it. Was an awesome car though but struggled to get 25 MPG.

My Superb with Eco remap and 60+ mpg is just fine

Thanks for your time replying anyway!

An XJR perhaps??

Even regular Shell is better than Sainsbury's stuff. My car definitely runs better and delivers better mpg on branded stuff, particularly Shell. I have never tried V-power diesel. It's mostly GTL (gas to liquid) sourced, so literally no sulphur and high energy density and high cetane number, which reduces ignition delay and maximises engine work on the crank reduces smoke and exhaust temperatures and maximises fuel economy. It's all good stuff but expensive at that too. Tempted to try MIllers EcoMax cetane booster soon, many people claim 10% improvement in mpg.

got bottle of redex-diesel so after tank of v-power will try redex and then one tank of normal and then will try Millers ECOMAX

I've seen elsewhere that you might need to do a few tank fulls to allow the ECU thingy to adapt to what you're putting in. I can't say whether that's correct or not.... but if it is what you're thinking of doing might not show any differences accuratly?

I'm not suggesting what you're doing is incorrect, just don't want you potentially wasting your efforts/money if it takes a while for the car to adapt and get the benefits.

What do you think?

Cheers

ade

I've seen elsewhere that you might need to do a few tank fulls to allow the ECU thingy to adapt to what you're putting in. I can't say whether that's correct or not.... but if it is what you're thinking of doing might not show any differences accuratly?

I'm not suggesting what you're doing is incorrect, just don't want you potentially wasting your efforts/money if it takes a while for the car to adapt and get the benefits.

What do you think?

..

You may be right actually but I just wanted to clean up the fuel system

So may be after my process of few tanks full I'll stay with Shell-fuel

and may be use one specific additive