David_1984 said:

Number 1 was mixed fuel. I filled up when the tank was nearly empty with V-Shell.
2 and 3 were using V-Shell.
Yes your right about the 38.80L bit.

By the way, I reset the trip computer? to zero when the fuel is halfway (measuring it on a flat road) and mark it down on a computer program. Thats the way I measure the fuel.

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2009/04/15 21:20
Your readings suggest you’ve improved your mpg from around 37mpg to 44mpg – but I’d argue there’s not enough data to be accurate. As you say, your first reading is a mix (95RON & V-Shell) – so we don’t really know what mpg you were getting on 95RON.

We would need something like 6 readings on purely 95RON fuel to get some degree of accuracy. For example, my last six mpg figures for my ‘54 Mk2B (1.2/8v) on 95RON (Conoco/ASDA) just prior to sale in Jun 08 were: 58, 39, 66, 54, 50, & 54 – which illustrates that one lone reading may not be reliable. My last six mpg figures for my current ’56 GP (1.2/8v) – same engine, heavier car - on the same fuel are: 51, 48, 45, 50, 53 & 51. (The readings are not trip computer based – but calc. from brim2brim … on [fuel low] warning absolutely filled to capacity until pump nozzle shuts off).

Similarly we’d need several readings on purely V-Shell to iron out any inaccuracies. Will you continue to record your data … 4, 5, 6? But say you do, we’re still unable to accurately measure any improvement given we only have one mixed fill to measure against.

I tend not (up until now) to use the [trip] much on my GP – but I do zero it at a brim-up & check the range read-out … usually shows around 500 miles. I also sometimes leave it on showing av.mpg or mpg just out of interest.

The cross-over issue (qisback) is one I’ve not heard before. I did talk with a Conoco tanker driver about a month back & he claimed that all refinery fuel (petrol & diesel) flowed thro the same pipelines. He said the practice of the tanker driver in-putting the additives at the point-of-sale (from the tanker) was history - & that now all petrol was the same 95RON until receiving the additives. He also claimed that higher octane petrol was still 95RON based petrol with more additives. If I recall his figures correctly – I believe he said his tanker took 33K litres of 95RON with 15 litres of additives.

Ok so here's my fuel consumption from April 2008.

David_1984 said:

Ok so here's my fuel consumption from April 2008.

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2009/04/15 22:16
Taking your `last 10’ on Morrison’s fuel, shows an average of 40mpg - & your `last 2’ on V-Shell, shows an average of 40 mpg. (That's not to say that mpg is the only consideration). Let it run & lets see what happens over time.

Update 209/04/15 23:04
Just had another squint at your data - & if you go back further to the `previous 10' you're averaging nearly 42 mpg on (presumably) Morrison's fuel.

Caravadossi said:

2009/04/15 21:20
The cross-over issue (qisback) is one I’ve not heard before. I did talk with a Conoco tanker driver about a month back & he claimed that all refinery fuel (petrol & diesel) flowed thro the same pipelines.

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Yes as far as I'm aware this is true they also use the same pipes for delivery, tanker drivers normally wash the desiel pipes out with unleaded on the drops.

i.e. if they drop 5 pods, 2 desiel and 3 unleaded (any sort) dependant on the recieving tanks they will drop the 2 desiel first then finish with the unleaded to wash the pipes out, this means they don't have to cap the pipes off. Bare in mind that tankers can only drop 2 pods at the same time.

The cross over problem doesn't happen often because the driver can get sacked for causing a crossover (especially if they don't report it), so they also put the resonsibilty on the onsite delivery supervisor (petrol station staff) as well meaning they both have to agree on a drop before it happens.

I've seen cross overs happen about 5 times in the years I was working for various petrol stations, with 1 just topping the tank off and 2 redistrabuting the fuel. The other 2 pumped the entire tank and set it back to the refinary.

Surely petrol is the same regardless of where you purchase it from? I get mine from Sainsbury's and Esso and sometimes BP. I don't understand why there's meant to be a difference, but as long as it makes the car run, I don't care.

Caravadossi said:

2009/04/15 22:16
Taking your `last 10’ on Morrison’s fuel, shows an average of 40mpg - & your `last 2’ on V-Shell, shows an average of 40 mpg. (That's not to say that mpg is the only consideration). Let it run & lets see what happens over time.

Update 209/04/15 23:04
Just had another squint at your data - & if you go back further to the `previous 10' you're averaging nearly 42 mpg on (presumably) Morrison's fuel.

Click to expand...

Shame I can't do this because I'm looking for a new car tomorrow