Premium fuels versus standards

[saint-spoon]

I am not normally someone who goes far out of their way to save a penny on a litre of fuel nor am I one for shelling out for the premium fuels being sold on the forecourts of many garages. I did however put half a tank of premium diesel into the tug yesterday and it struck me this morning on my commute to work that the mpg reading on the dashboard had jumped from mid 30s to over 40mpg. Taking into consideration the additional cost of the premium fuel and the fact that the mpg dashboard indication is probably not the most accurate measure of fuel efficiency that gives an increase of efficiency of around 15% or in monetary terms 30p for and extra 5 miles. I wonder if that translates into a true saving or not.
I am not convinced however I shall see how it translates when I am next towing the c-van.

 

[Mike_S]

"Honest John" in the motoring section of the Saturday Telegraph has long been an advocate for improved mpg using premium diesel. I have run my Seat Alhambra almost exclusively on Shell premium diesel and found I do get better mpg than using standard fuel. A good few months ago I did run 3 or 4 consecutive tankfulls of standard fuel by way of comparison. Consumption using premium fuel was improved enough to cover the extra cost - using a Shell drivers club loyalty card also helps reduce the difference by 1p /l. Not sure how performance in terms of acceleration, etc is changed because I use my right foot sparingly. Honest John also reckons that premium fuel is better for injectors, etc.

My wife has a petrol Mazda 2 and it pulls much better when running on premium fuel. Not sure about mpg - my wife is not so bothered about keeping fuel and mileage records as I am with the Alhambra.

 

[Hutch]

I know that I get better mpg in my Santa Fe if I use " Branded" fuel ie shell, Elf, BP etc, rather than Supermarket fuels, might try the premium and see, A sudden hop from mid 30's to 40's cant really see it happening unless you have done less than about 20 miles from resetting the on board computer. On the Santa Fe, but saying that, if your driving around town and then do a 100 mile trip at say 65 mph, it will change the average mpg.
I will fill up with pemium and see what happens.

 

[Raywood]

I have seen posters try to work out if there was a saving by using the premium fuel. The conclusion was the extra mileage claimed gave you roughly the same cost per mile so there was no saving. If as they say the engine runs cleaner it might however save you a big repair bill at some time.
It is almost impossible to be sure of comparisons though as the driving after two tankfuls is never the same and you always are mixing the fuel with what is already there. The only thing I can say is that I fill the car up before long towing trips and Tesco Diesel seems to be giving me the best mileage but not conclusive.

 

[ProfJohnL]

As Ray points out the variables affecting MPG are quite astounding so its almost impossible to produce andy sort of conclusive evidence for improvements except by fully controlled testing.

To some extent the perception about fuel economy can be a self fulfilling prophesy. You fill up with what you expect might improve your mpg, but you are therefore more conscious of it and subconsciously be more sparing with your right foot.

The longer you can run the test the more realistic it will be.

 

[Mike_S]

As Ray points out the variables affecting MPG are quite astounding so its almost impossible to produce andy sort of conclusive evidence for improvements except by fully controlled testing.

To some extent the perception about fuel economy can be a self fulfilling prophesy. You fill up with what you expect might improve your mpg, but you are therefore more conscious of it and subconsciously be more sparing with your right foot.

The longer you can run the test the more realistic it will be.

I quite agree. This is why I used certainly 3 but probably 4 consecutive tankfulls to confirm my findings. Each tankfull represents the best part of 600 miles with my Alhambra. Unfortunately can't find my records to quote chapter and verse!
Mike

 

[Jaydug]

Some years ago on another forum we had a member (Robert Jackson) who had spent his working life as a chemist in the petro-chemical industry and when he met his untimely death a few years ago, he was the UK representative on CEN WG9 – The EU Standards Committee for all motor vehicle fuels. Just before he died he wrote this essay:-

All pump fuel in Europe is produced to meet the relevant EN standard - which you will see written on the pump body.

The major difference between the supermarket fuels and the branded fuels is the exact nature of the additive pack added to the fuel when it leaves the refinery - common rail pump lubricants, injector cleaners, etc.

Synthesised Diesel
The exception to this is the new "synthesised" diesel fuels, such as BP Ultimate (actually researched by Aral in Germany), Shell V-Power (may be called something else in the UK), and Total Excellium. These fuels are manufactured in the refinery by joining simple petroleum hydrocarbons into an exact diesel fuel - you'll need some experience of university level Chemistry to follow what they do - so just accept that they are better - higher cetane rating, better additive pack, etc.

Normal Diesel
This is a straight distillation fraction from crude oil, produced by the nearest refinery to the fuel depot - so for instance, diesel refined by Shell may be sold by any of the other retailers close to that Shell refinery. The major difference is the additive pack - which is brand specific - and any specification difference imposed on the refinery by the other retailers - and the addition of bio-diesel.

Bio-diesel
Another one of our EN committees, pump bio-diesel is a blend of normal refinery diesel (95%) and (5%) of pure bio-diesel. This is an EN standard and all EU countries will be (or are) selling this bio-diesel as a direct replacement for normal diesel.

All the car manufacturers have accepted this 95:5 blended fuel, and we are working on specifications for a 90:10 blend.

Pure bio-diesel is manufactured by mixing and heating vegetable oil with methanol (methyl alcohol) and sodium hydroxide (caustic soda). This splits the vegetable oil into glycerine and fatty acids, which immediately reacts with the methanol to form a "fatty acid methyl ester" or FAME (bio-diesel).

FAME is perfectly fine as a diesel fuel, it has very good lubricating effects - and replaces the lubricant additive in a normal diesel fuel - except that it is not as stable as normal diesel - it tends to go "sour" or "rancid", which is why the car manufacturers don't like you to run a car on pure bio-diesel. Not a problem as a 95:5 blend.

Vegetable Oil
Reasonably OK for an old (pre 1995) diesel engined car - except that the car won't start on cold vegetable oil, but once the engine is running it's OK.

Other problems are that vegetable oil quickly turns in a gummy glop (like the linseed oil that artists use) and the car's fuel system and that the engine needs a lot more maintenance - blocked injectors, gummy residue in pumps and cylinders, etc.

After market additives
After market products like Millers improve the cetane rating of standard diesel, but only when the engine is cold - interestingly it doesn't help a hot engine - so cold starting is usually quieter but no difference to a hot engine - and Millers does provide good, additional pump lubricity.

Self Tuning Engine Computer
So, if your diesel engined car "self tunes" then try Shell V-Power, BP Ultimate, Total Excellium - I see between 3% and 5% improvement in fuel consumption. My Mercedes C270 returned 52.8 mpg driving from Rotterdam to Wendover yesterday - on Dutch Shell V-Power - 320 miles at speeds of around 60, 70 and 80 mph depending on the country / road speed limit - using the electronic speed limiter.

If not, stick with the regular diesel fuel, and add Redex or Millers at the recommended dosage level - adding more won't improve the performance.

And don't be dismissive of supermarket fuel, it can and often is identical to branded fuel.

And if you add Redex or Millers or switch to a branded fuel, then any change to the cleanliness of the injectors won't show itself for quite a few hundred miles, but pump lubrication and maybe a higher cetane rating will show an effect much sooner - depends how much old fuel was in the tank and fuel lines - and how much the old fuel dilutes the action of the new fuel.

So is there a difference between supermarket and branded fuel ? - there can be - but often there isn't.

How can you tell if one fuel is better than another?

To compare the fuel consumption, you need to exactly reproduce two journeys - exactly the same speed, exactly the same acceleration and braking, and under identical conditions:

Atmospheric Pressure
A one percent change in air pressure has an identical effect on power and torque - so driving on days with high pressure makes the engine generate more power

Temperature
Driving on hotter days reduces engine power.

Humidity and Rain
Driving on days when it is humid or raining significantly improves engine power - water injection is used in truck racing and sucking in damp air has a similar effect in increasing power.

These produce percentage level effects on mpg - making it difficult for the driver to make comparisons. Driving on a cold, damp day may see an improvement of 3% or more compared to a hot, dry day.

Even more important are the effects of different traffic levels and the inability of drivers to EXACTLY reproduce a journey on UK roads, for instance:

Speed
A 1 mph increase in speed (say 60 instead of 59) will make about a 2% difference in fuel consumption - rolling friction and wind resistance increase exponentially - on top of the extra fuel need to spin the engine that bit faster.

Unless you drive everywhere using an electronic speed limiter or digital cruise control then it's impossible for most drivers to reproduce even a constant speed.

Acceleration and Braking
Big percentage differences here - and unless you are driving on an empty test track - the effects of other traffic, let alone how you drive the car, have effects at least as large as the difference attributed to different fuels.

Summary
There is a reproducible improvement of between 3% and 5% by buying the synthesised diesel fuels - BP Ultimate, Shell V-Power, Total Excellium, etc - compared to the standard branded diesel fuels.

There are smaller differences between supermarket and standard branded fuels - sometimes they are physically the same fuel - sometimes they differ only by the additive (cleaner) pack - and sometimes they are different.

Day to day variations in the weather, driver reproducibility and traffic make it very difficult for drivers to reproduce journeys.

Comparing two fuels
If you do want to make a comparison, drive your car until the fuel tank is almost empty, then fill the tank and after you have driven 200 miles (any old fuel should have been used up), drive at a fixed speed on a motorway for 10 miles and record the fuel consumption.

Then the next time you fill up, repeat the exercise with a different brand of fuel - but remember to test on exactly the same section of motorway and on a similar day.

Checking your fuel consumption over normal driving, in stop start traffic, over a period of weeks - just tells you that you have had to drive differently.

Finally, don’t rule out the placebo effect!

 

[JonnyG]

excellent post . could i just point out without getting my head bitten off the following paragraph below does not make any sense with regards trying to compare 2 fuels mpg.. as it is as error redden as any other method suggested. ie still not a controlled environment , and the distance used, only 10 miles? no mention of how you record the fuel consumption surely not suggesting using the trip computer to work out an average mpg? Frankly there isn't a system that is fool proof but the longer the distance the ave is taken over, the better. 10 miles? waste of time.

"Comparing two fuels
If you do want to make a comparison, drive your car until the fuel tank is almost empty, then fill the tank and after you have driven 200 miles (any old fuel should have been used up), drive at a fixed speed on a motorway for 10 miles and record the fuel consumption."

 

[chrisbee1]

excellent post . could i just point out without getting my head bitten off the following paragraph below does not make any sense with regards trying to compare 2 fuels mpg.. as it is as error redden as any other method suggested. ie still not a controlled environment , and the distance used, only 10 miles? no mention of how you record the fuel consumption surely not suggesting using the trip computer to work out an average mpg? Frankly there isn't a system that is fool proof but the longer the distance the ave is taken over, the better. 10 miles? waste of time.

"Comparing two fuels
If you do want to make a comparison, drive your car until the fuel tank is almost empty, then fill the tank and after you have driven 200 miles (any old fuel should have been used up), drive at a fixed speed on a motorway for 10 miles and record the fuel consumption."

For the purpose of comparing 2 fuels it won't matter if the car's trip computer is reading incorrectly so long as it reads out by the same percentage for both trips.

 

[JonnyG]

excellent post . could i just point out without getting my head bitten off the following paragraph below does not make any sense with regards trying to compare 2 fuels mpg.. as it is as error redden as any other method suggested. ie still not a controlled environment , and the distance used, only 10 miles? no mention of how you record the fuel consumption surely not suggesting using the trip computer to work out an average mpg? Frankly there isn't a system that is fool proof but the longer the distance the ave is taken over, the better. 10 miles? waste of time.

"Comparing two fuels
If you do want to make a comparison, drive your car until the fuel tank is almost empty, then fill the tank and after you have driven 200 miles (any old fuel should have been used up), drive at a fixed speed on a motorway for 10 miles and record the fuel consumption."

For the purpose of comparing 2 fuels it won't matter if the car's trip computer is reading incorrectly so long as it reads out by the same percentage for both trips.

and we will assume it will do that because? .
you cannot ... basically what i read was the replacing of one flawed but acceptable system for measuring mpg and making comparisons ,with one that's just as flawed if not worse..but hey just my opinion. ..
oh i use the premium brand fuels BP and shell offer. mainly in the hope they help keep things cleaner in the engine department.but.as for the the better MPG claims? well i doubt it at least the shell stuff whilst it does have a 1 to 2 higher cetane rating the fuel itself is less dense than normal diesel . so off setting any advantage,in theory.

 

[Gafferbill]

.........and surely the main point of interest is the cost of use of which fuel consumption is just a part.
My most cost effective car was a 20 year old VW 1048cc Polo which cost £375 to buy. I kept it 5 years, it did 20,000 miles and cost £100 in maintenance.It did 40mpg and I sold it for £225.
I now have a fairly new diesel Ford as a runabout that does 55 mpg........ nowhere near as cheap to run as the old Polo!!

 

[Dustydog]

There is a 10 -15p per litre difference between the two.
I doubt overall there will be any real significant gain other than perhaps less wear on injectors and pumps.
The water /steam systems have an appeal but I guess they are expensive and not readily available.

 

[ProfJohnL]

There is a 10 -15p per litre difference between the two.
I doubt overall there will be any real significant gain other than perhaps less wear on injectors and pumps.
The water /steam systems have an appeal but I guess they are expensive and not readily available.

I know these figures are not exact but it will give a ball park figure. Based on a vehicle 30mpg typical mileage, the additional cost of using premium blends will be about 2p per mile. A car that does 10K miles per year will spend an extra £200 on fuel. If that extra spend saves the need to replace injectors (£250 each) and or fuel pump (£800 to £1000), then it's a reasonable investment.

But if the car is covered by warranty then its money wasted.

 

[WoodlandsCamper]

When I first had a caravan I towed it with a 1.8 petrol Cavalier. After about a year I changed the tug to a 1.8 petrol Vectra and the fuel consumption (dropped from average 40 mpg to 30 mpg) and power when towing were abysmal compared to the Cavalier. I tried a few tank fulls of premium petrol and the extra power when towing was very noticeable, but I can't remember if the fuel efficiency improved.

 

[Dustydog]

There is a 10 -15p per litre difference between the two.
I doubt overall there will be any real significant gain other than perhaps less wear on injectors and pumps.
The water /steam systems have an appeal but I guess they are expensive and not readily available.

I know these figures are not exact but it will give a ball park figure. Based on a vehicle 30mpg typical mileage, the additional cost of using premium blends will be about 2p per mile. A car that does 10K miles per year will spend an extra £200 on fuel. If that extra spend saves the need to replace injectors (£250 each) and or fuel pump (£800 to £1000), then it's a reasonable investment.

But if the car is covered by warranty then its money wasted.

My warranty is long expired.aHowever I do use a proprietary additive to the fuel tank every six months. About £5.00 a go.
my last car treated this way did 136k before I traded it. No problems with injectors or pumps.

 

[MichaelE]

I have always used branded fuels but never the premium stuff as i could never feel any benefit, although when i had a fuel card the BP stuff had double nectar points and one of my Audi's used to run on 98 octane.
I have had an issue with supermarket fuel on my car, once it went into limp mode on the way home , re started no fault logged and thought nothing of it a few months later it happen again and realized we had filled up both times from Tesco's when they were doing the 25p off a litre.

 

[saint-spoon]

I think that the key thing here is that my observation lacked any credibility either scientifically or from the perspective of an engineer. The MPG meter has also dropped down to mid 30s again which in no way reflects a loss of economy over the long term, it’s just that I have been doing short distances around town.

 

[ProfJohnL]

I think that the key thing here is that my observation lacked any credibility either scientifically or from the perspective of an engineer. The MPG meter has also dropped down to mid 30s again which in no way reflects a loss of economy over the long term, it’s just that I have been doing short distances around town.

I don't think there is anything wrong in trying to do an MPG check, its just that all too often people will do a check and perhaps not realise how many variables have been involved and will mask the reality of the fuels impact on MPG. However if you do get a difference difference in your recorded MPG well that's good however it came about.

 

[chrisbee1]

I have always used branded fuels but never the premium stuff as i could never feel any benefit, although when i had a fuel card the BP stuff had double nectar points and one of my Audi's used to run on 98 octane.
I have had an issue with supermarket fuel on my car, once it went into limp mode on the way home , re started no fault logged and thought nothing of it a few months later it happen again and realized we had filled up both times from Tesco's when they were doing the 25p off a litre.

Did you get the car repaired? If it won't run correctly on supermarket fuel there's obviously a fault with it.

 

[MichaelE]

I have always used branded fuels but never the premium stuff as i could never feel any benefit, although when i had a fuel card the BP stuff had double nectar points and one of my Audi's used to run on 98 octane.
I have had an issue with supermarket fuel on my car, once it went into limp mode on the way home , re started no fault logged and thought nothing of it a few months later it happen again and realized we had filled up both times from Tesco's when they were doing the 25p off a litre.

Did you get the car repaired? If it won't run correctly on supermarket fuel there's obviously a fault with it.

It was checked out and it didnt log any faults, the only conclusion was that the previous fill ups were Tesco fuel. Never had an issue with the car before or since as i have never used Tesco fuel again.
All base fuel is the same its the additives that make the difference.