We have all read those consumer stories about, for example, people in the tropics who don't realise that they may be pumping their cars full of hot air, literally. The science is simple: when petrol heats up in the storage tanks, it expands, becoming less dense.
So there is plenty of advice telling motorists that even the time of day they fill their cars can have an impact early mornings being cheaper for the average motorist. The difference per visit is very slight, but over a year, it can add up, goes the theory.
I've done some of my own adding up. The number of vehicles on Britain's roads has reached an all-time high. As the DVLA says, this is nothing new. Every year since World War II sees another all-time high. At the end of 2012 there were 34.5 million vehicles licensed for use on British roads, of which 28.7 million (83%) were cars.
Now, given that there are fewer than 9,000 forecourts left (down from 37,500 in 1970), it stands to reason that, with the amount of fuel those stations are handling, temperature changes and density of fuel becomes something that can add up very quickly indeed.
Dipsticks are no longer used to measure petrol so you have to accept what the pre-loading ticket says. If you order however many thousand litres then that is what the ticket says and that is what you hope you get. As Phil Monger, technical director at the Petrol Retailers Association, says: "More transparency is needed."
I had an anonymous tip on the subject with the retailer claiming discrepancies between what was ordered and what was delivered but equally there have been others who have reported how scrupulous their supplier is.
So, what if anything, can be done? I asked Steve Coombe of fuel management company BigOil for a comment since the website (www.bigoil.net) contains subscribers' comments that mention savings of tens of thousands.
He gave me a little commercial: "Will just say and quote unashamedly that our new website portal BigOil powered by Vianet is the perfect answer for retailers.
"It now combines the Big Oil Platts pricing feature to confirm 'contract pricing' but, with the wet stock element, provides the retailer with the actual litres delivered underground taking temperature effect into account."
He explained that it therefore confirmed actual product delivered along with the comforting thought that the correct supply price has been applied.
And finally he adds: "Human error in pricing does happen and we find that there are approximately 10 anomalies a year for a typical forecourt."
Ga-a-ah! A tricky one
'Gassing around' (GA) has emailed me again. He gets in touch every so often with a rant or a query or even a tip. I have no idea who he is or where he is and I'm really only guessing at his gender (probably a bloke though, even though he has admitted to liking that air of mystery). He writes: "Got an Asda not far away which is going to offer Click & Collect. I'm relaying the store, on a shoestring. Any ideas?"
My first one was to ask whether he belonged to any group because that makes a difference. He replied: "No, totally indie and indignant. Why else would I be asking you?"
These days when the reps' visits are rapidly drying up, it is sometimes difficult to sort out your layout but the reps were always biased anyway (although offered good promotions and freebies at times). No doubt P&H (which, I am guessing, does the deliveries) brings point-of-sale material too.
P&H does, for example, offer category advice in the key area of news and mags, a complex one. The advice comes with planograms, a helpline and sales reports.
If GA goes to the cash and carry for supplies, there will still be pos and planograms available. In addition there are websites, apps and of course, this magazine and our sister paper Convenience Store, never short on layout advice. In fact, c-store retailers rack up an estimated £1.2bn of lost sales each year because the stocks are wrong or not there at all. You might think you know your best sellers but an electronic analysis can be quite revealing.
There was some interesting insight into how shoppers shop reported a few months ago in The Grocer magazine. Real proper technological stuff tracking shedloads of shoppers. Turns out they don't look at those promos by the front door too busy sorting out the list, the trolley, checking their mobiles.
In forecourt c-stores though, I reckon the old rule still applies in many cases. They buy petrol, they come in and queue, and they reach out for anything else at arm's length. If they are hungry too, they will wander over and look at the fresh so make sure it is and have all the snackie, sweetie, drinkie stuff alongside.
Men apparently like red in store, so if you use pos well, let some of your store blush!
Keep it all spotless regularly 'walk the store' as though it belonged to someone else. You might surprise yourself.
And finally, GA shouldn't worry too much about click & collect yet. The Institute of Grocery Distribution says it is still a niche market. It conducted a study which showed only 3% of shoppers used it.
But Asda's doing it and so is Tesco, so it is one to watch out for.