Brimming the tank also needs to be done when the car has been sitting cold for a decent period of time (like overnight). Pretty much all cars put warm fuel back to the tank which makes the fuel in there expand. You will always get a little more in at the same level with cold fuel in the tank.

Statistically trying to get accurate fuel economy numbers from ~4 gallons of fuel is pretty much impossible. 3 tanks is where the errors and deviations from each fill start to even out.

I can get +/-10% on my vehicles (no trip computers, done via fill-up) fuel consumption on any given tank. But if one tank is high, the next is low and the overall average doesn't change much apart from summer vs winter.

My vehicles give their best fuel economy on hot trips. Like 35C.

As far as I am concerned, diesel fuel is diesel fuel and I haven't found any provable variation over here. WIth petrol octane plays a big part (particularly on high compression or boosted engines).

I was basically trying to say the compass (polar axis) does not dictate incline.

That's so disappointing. I find if I'm driving say from Birmingham south down the M5 I can virtually freewheel to Bristol. Maybe there's a following wind. Doing the journey on a Tuesday seems to help. I don't know why this should be.

(For those who don't do 'silly' yes this and my previous post were not intended to be serious! I apologise for any confusion caused and I don't really believe the our little island is on a slope.)

That's so disappointing. I find if I'm driving say from Birmingham south down the M5 I can virtually freewheel to Bristol. Maybe there's a following wind. Doing the journey on a Tuesday seems to help. I don't know why this should be.

I quite agree with you here. Every time I drive from Bristol to Brum & back, which is every few months, I always, without fail, get about 3-4mpg greater on the journey when heading South. You really can just feather it.

My logic says that the start of my journey is a few miles of central Bristol, and quite a bit of stop/start traffic with a warming up engine. Destination is usually just off the motorway at J3. Return leg means Bristol stop/start bit is done with a nicely warmed up engine.

This is quite interesting actually. I always use my local BP for petrol and even though my car is a 1.2 it is quite punchy and responsive. But I filled up with petrol in Tesco today and it feels sluggish and unresponsive. I intend to fill up with BP this weekend but I will let you all know. Coincidence or what?

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No conincidence! It's rubbish! I get 50 miles less to a tank using Tesco!

i second that! i always only ever used shell fuelsave diesel in my humble 1.4 tdi fab,due to my dad saying it was better fuel and the fact that the shell is about 60 seconds from my front door! that was until my shell shutdown for a refurb. so i had to use tesco fuel for 5 weeks, and ive been getting only 118-120 miles off each £20 refill since, now after using shell fuelsave diesel again for 3 weeks, and flushing that crap out my engine im again getting 148-150 miles driving from £20 of fuel. which equates to about 65 miles to a tank. i wont be using supermarket crap again! also sorry to higjack a topic, but could i use the millers stuff mentioned before in my fuel to?

i second that! i always only ever used shell fuelsave diesel in my humble 1.4 tdi fab,due to my dad saying it was better fuel and the fact that the shell is about 60 seconds from my front door! that was until my shell shutdown for a refurb. so i had to use tesco fuel for 5 weeks, and ive been getting only 118-120 miles off each £20 refill since, now after using shell fuelsave diesel again for 3 weeks, and flushing that crap out my engine im again getting 148-150 miles driving from £20 of fuel. which equates to about 65 miles to a tank. i wont be using supermarket crap again! also sorry to higjack a topic, but could i use the millers stuff mentioned before in my fuel to?

The problem with this is fuel prices change so your data is worthless as fuel prices have peaked and gone back to the feb 2012 level in recent weeks. This is why people calculate mpg and not distance per £20. Also if you're only putting £20 in you have no fixed point of reference, fuel light coming on isn't as accurate as a vented fill for example.

Yes you can use Millers in your diesel but again it's easier to calculate how much per tank for exactly the same reason mentioned above.

As well as the pounds changing size, tank-fills tend to vary as well. Calculating volumes (litres or gallons) against distance is the only consistent way.

Edited 23 May, 201214 yr by Kiwibacon

All crude in to UK refineries is the same (there is an established acceptable range for certain attributes). All petrol/diesel out the other end is the same (within an accepted range).

The tankers line up, fill up with petrol and then add 'additives' relevant to who's buying the petrol. Therefore the base petrols all the same there is no concept of Shell say getting the 'good' stuff.

None of the oil majors owns tankers any more. They are all sub-contacted out. They may carry an oil companies livery but they don't own or run the tankers. I'm not sure if Tesco's own their own tanker or not. Don't think it matters.

All sellers are party to a net fuel agreement whereby they swap fuel if someone has an unexpected shortage. They are one or two fuels outside the agreement such as Optimax but nearly all are in it.

So the only difference between supermarket fuel and branded fuel is the 'additives' unless you happen to be filing up with swapped fuel in which case you could be buying Tescos fuel at a Shell station or vice versa.

The oil majors have never made any claims in their advertising that these 'additives' do anything as if they did they would have to prove it.

It does seem that the refineries have an agreement to supply each other based on location. This is to reduce the amount of road transportation of the fuel. So who actually supplies who depends on how close they are to a specific refinery. As an example, all fuel here in Scotland originates from Grangemouth (which is BP owned) no matter what the forecourt badge says.

Once I spoke to a guy who is fairly senior in Tesco management. It was a few years back about three/four years ago and he told me that Esso had the contract to supply Tesco.

I have Tesco almost next to me and over the last 5+ years never had a single issue. Over the years I've seen almost all the brands name tankers supplying them, so for me is the price and the points

Recently I went to London and back and there was not a difference on the MPG at all. Going south on Tesco, driving north on BP.

You pay your money and you make your choice...

I think shell fuel save diesel is the nuts. That's the only thing I put in my vrs.

The oil majors have never made any claims in their advertising that these 'additives' do anything as if they did they would have to prove it.

http://www.shell.co....uelsave/diesel/

http://www.tesco.com...ts-overview.asp

The name 'Shell Fuelsave' is pretty clear but while they don't state every person will get x more miles per tank as they haven't tested it in every possible car/engine designed but they do suggest it. BP, Shell and Tesco (probably everyone else but i've not looked up the details) all claim additional cleaning properties from the additive packages and have proven it, BP used to have an info pic on a Focus engine after xx thousand miles and then stripped the same engine after xx thousand on nothing but BP ultimate and it was significantly cleaner. Personally I get better results with Shell petrol on car's/bikes set up to benefit from it.

Shell Fuelsave is 'enriched with Shell Efficiency Improver'. Reminded me of PAL dog food. 'Enriched with nourishing marrowbone jelly.' Or 'cotton rich' socks for Christmas. Try 'Farm Assured' M&S red diesel for fun with Customs and excise. And if Carling made diesel would it be 'probably the best diesel in the world'.

As someone has already said you pays your money. If you think one brand of fuel is the mutts then use it.

I think shell fuel save diesel is the nuts. That's the only thing I put in my vrs.

Why do you think that?

The problem with this is fuel prices change so your data is worthless as fuel prices have peaked and gone back to the feb 2012 level in recent weeks. This is why people calculate mpg and not distance per £20. Also if you're only putting £20 in you have no fixed point of reference, fuel light coming on isn't as accurate as a vented fill for example.

Yes you can use Millers in your diesel but again it's easier to calculate how much per tank for exactly the same reason mentioned above.

Using the light as a reference each time is accurate, no more or less variables involved than brimming as this changes each time too. I find usin the light accurate as each time I Calculate my figures are accurate and match that of when brimmed for example.

...I find usin the light accurate as each time I Calculate my figures are accurate and match that of when brimmed for example.

Neither method is very accurate. The light can come on going around a roundabout/corner. Using the same pump each time helps but there is a small variation. The temperature makes a difference too.

The important thing is to do the measurement over a full tank of fuel, so the error is less.

The only way to get really accurate results, is to drain the tank and fill with a measured volume of fuel at a known temperature

Shell Fuelsave is 'enriched with Shell Efficiency Improver'. Reminded me of PAL dog food. 'Enriched with nourishing marrowbone jelly.' Or 'cotton rich' socks for Christmas. Try 'Farm Assured' M&S red diesel for fun with Customs and excise. And if Carling made diesel would it be 'probably the best diesel in the world'.

As someone has already said you pays your money. If you think one brand of fuel is the mutts then use it.

Neither method is very accurate. The light can come on going around a roundabout/corner. Using the same pump each time helps but there is a small variation. The temperature makes a difference too.

The important thing is to do the measurement over a full tank of fuel, so the error is less.

The only way to get really accurate results, is to drain the tank and fill with a measured volume of fuel at a known temperature

I'm not THAT concerned lol

Using the light as a reference each time is accurate

....only in la la land

Tesco had some company produce a pseudo-scientific report on their Momemtum 99 stuff, saying how it improved MPG etc, even on cars not specced for the higher octane fuel. I gave it a go and found there was no advantage whatsoever. Have tried Shell Fuelsave a couple of times, and it seems to help. Not done so recently as my nearest petrol stations are a rather expensive Texaco, and a Tesco and Morissons. The nearest Shell with reasonable prices is a bit out of my way.

Using the light as a reference each time is accurate

Going around a corner or up/down hill can bring the light on.

Edited 23 May, 201214 yr by anewman

I'm not THAT concerned lol

But you are basing some big claims off that inaccurate method.

It's not inaccurate, it's easy to tell when the light comes on round a corner, cause it goes off again on the level! Lol

Neither method is very accurate. The light can come on going around a roundabout/corner. Using the same pump each time helps but there is a small variation. The temperature makes a difference too.

The important thing is to do the measurement over a full tank of fuel, so the error is less.

The only way to get really accurate results, is to drain the tank and fill with a measured volume of fuel at a known temperature

I kinda disagree. Either method over a period of time IS accurate.

As a one off, definitively not.

i find running the vrs on tesco diesel it smokes a lot more and i get about 4-5mpg less, now have emmision lamp on due to sticky egr valve, and have gone back to shell / esso diesel and it is now intermittently going out for periods on an increasing regular basis, indicating to me the decent stuff is slowly unclogging the egr valve

Edited 24 May, 201214 yr by bluecar1

i find running the vrs on tesco diesel it smokes a lot more and i get about 4-5mpg less, now have emmision lamp on due to sticky egr valve, and have gone back to shell / esso diesel and it is now intermittently going out for periods on an increasing regular basis, indicating to me the decent stuff is slowly unclogging the egr valve

You have an EGR valve problem that is unrelated to fuel. The EGR valve only sees soot, it can't be unclogged by a different brand of fuel.

Maybe the valve sticking open (which causes more smoke) co-incided with a tank of supermarket diesel. But correlation =/= causation.

A bit off topic and showing my age perhaps. The year 1952, The car:- Humber Super Snpe MkI with a Stromberg carburetter, it would only run on National Benzole and nothing else. BP Super Plus, Cleveland, Esso Golden (put a tiger in your tank) were all rubbish and the bloody car would have difficulty even starting. Petrol was then 4/2p a gallon. Bring back National Benzole.

Edited 24 May, 201214 yr by hussarman