Cost vs Quality in petrol

TwittersPVFC

All,

Thought I'd run this past all the experts on here see if it's just me or others have experienced the same. I've found in the last couple of months that while supermarket petrol is cheaper, it actually costs me more in the long run. Allow me to explain the wierd logic behind this!

Since I purchased a new car in August, I started recording the amount of petrol I was using so that I could make sure I was keeping within my budget. This included where I bought the petrol from, cost per litre, amount of miles done and amount of litres filled up. I also recorded the mpg that my car's computer claimed I'd done and the amount I calculated I'd done from the amount filled up etc. It was only last week that I noticed a very strange pattern building up.

Since the 15th August, I've filled up 6 times. 4 times I've filled up at two different Shell garages, and twice at my local Tesco garage. When I've filled up at the Tesco garage, I've only been able to put 51 litres into my tank before I can get no more in. However, at a Shell garage I've been able to get in between 52 and 55 litres, despite the gauge being at roughly the same point when filling up.

The other item that I noticed was the miles per gallon I'd done. When I've filled up at a Shell garage, it's been consistently between 44 and 45mpg. However, when I filled up at Tesco it's been 42.1 and 38.3, despite doing the same journeys every day and taking care to monitor my consumption when driving.

Anyone else noticed similar trends?

lfc321

Not sure I follow your first point: obviously the amount left in the tank when you stop to fill up varies, even if the guage looks like it's at roughly the same point. Just so happened that when you filled up at Tesco you had more left in the tank. Not sure what the issue is here(?)

On the second issue: that's an interesting finding, although your sample size is very small. You're talking about quite small differences in mpg which could be due to different petrol, but equally could be due to a whole number of diffierent factors. Would like to see if the pattern continues if you average out over a longer period.

Idiophreak

I've little doubt that some fuel is better than others - but would be quite surprised if it's as much as the 10% you're reporting. Are you sure you weren't just late for work a couple of days or something?

maninthestreet

TwittersPVFC wrote: »

All,

Thought I'd run this past all the experts on here see if it's just me or others have experienced the same. I've found in the last couple of months that while supermarket petrol is cheaper, it actually costs me more in the long run. Allow me to explain the wierd logic behind this!

Since I purchased a new car in August, I started recording the amount of petrol I was using so that I could make sure I was keeping within my budget. This included where I bought the petrol from, cost per litre, amount of miles done and amount of litres filled up. I also recorded the mpg that my car's computer claimed I'd done and the amount I calculated I'd done from the amount filled up etc. It was only last week that I noticed a very strange pattern building up.

Since the 15th August, I've filled up 6 times. 4 times I've filled up at two different Shell garages, and twice at my local Tesco garage. When I've filled up at the Tesco garage, I've only been able to put 51 litres into my tank before I can get no more in. However, at a Shell garage I've been able to get in between 52 and 55 litres, despite the gauge being at roughly the same point when filling up.

The other item that I noticed was the miles per gallon I'd done. When I've filled up at a Shell garage, it's been consistently between 44 and 45mpg. However, when I filled up at Tesco it's been 42.1 and 38.3, despite doing the same journeys every day and taking care to monitor my consumption when driving.

Anyone else noticed similar trends?

No. This issue gets raised once or twice a year on these boards The research that has been performed comparing supermarker petrol vs. branded petrol has never indicated better MPG for branded petrol.

Ebe_Scrooge

Branded petrol may give you a marginal increase in MPG, due to the detergents etc. that are added, but the difference really will be absolutely miniscule. Driving style will have a far greater effect, as will the weather - having the windows open, or using any electrical equipment to heat, cool or light the car will marginally increase consumption.

Driving style will have the biggest impact though. A small increase in speed has a small but quite significant impact on consumption - going 10mph faster will use quite a lot more fuel ( within limits, the actual precise figures are very complicated to work out ). Hard acceleration and braking will likewise use an awful lot more than steady gentle driving.

So for the relatively small amount of journeys you're talking about, I would say the brand of fuel really would have no impact - at least, none that you could reliably measure.

vax2002

They are 11 petrol distribution depots in England
They ALL get the same petrol.

fivetide

The only difference I ever found was with the Scooby and using 99 RON stuff.

It seemed to go slightly and i mean very slightly further on Tesco 99 than it did on Shell Optimax. I think that might be because optimax (as was) used to vary in its RON rating which is whay they didn't put one on the pump.

5t.

LandyAndy

I usually run my Mazda2 on Esso petrol but sometimes use Waitrose (cheaper but not worth driving to specially). It doesn't make a noticeable difference to my mpg.

cardinalbiggles

vax2002 wrote: »

They are 11 petrol distribution depots in England
They ALL get the same petrol.

There's only 1 in Scotland and I keep telling people this. They used to add detergents to the fuel as it came from the refinery and that was it "branded"

Thing is nowadays additives are added to all fuels, and, this people don't understand, Supermarkets for example buy whatever is going cheap, that could be a batch of Shell or BP or any other that's coming out the refinery in tankers.

Sure the petrol is different but not that different otherwise your car wouldn't run!

forgotmyname

Problem is the same journey is not the same.

Traffic, Wind, Temperature all play a big part in the fuel consumption.

Gauges are not that accurate, You said the gauge is roughly the same.

Roughly the same is easily enough to be out by 5 litres.

Filling up between 4 and 6 times is nowhere near enough to get a proper average.

If you can done the test with 10 cars in a sealed lab with temperature control and fuel measured down the the nearest ml. I would have thought it was probably right. As long as all cars showed the same results of course.

PsiDOC

vax2002 wrote: »

They are 11 petrol distribution depots in England
They ALL get the same petrol.

That's a bit of a broad sweeping statement, and sadly incorrect.

There are 9 different Oil Refineries in the UK, 6 of these are in England, 2 in Wales and 1 in Scotland. I can also tell you that one of the ones in Wales has it's main distribution centre in england as well. So how can the distribution centres in England all get the same fuels if it is coming from at least 7 different places?

The quality of the fuels you put into your tank is governed by an extremely strict standard with regards it's actual components. These cannot be under certain levels and if they are then that product is deemed as off specification cannot be sold. The testing of the fuels is a continuous process with an independant body doing the final test prior to release from the bonded site. Yes the product can be over specification and the extra specification is classed as give away, however in this day and age the refining and blending processes are monitored very closely so that little or no give away is achieved as this means reduced income for the refinery.

Psi