"An inch of time is worth an inch of gold, but it is hard to buy one inch of time with one inch of gold"
Which always says to me that its not worth it just use the quickest option
Take the example drcongo posted:
"Yesterday I had to drive to a nearby town, just 20 minutes away, and noticed that every single petrol station there was a good 5p per litre cheaper than my town. I might plug this into a map."
Assume he uses 30 litres a week (high end of average UK usage) that's £1.50 per week saving but assume the extra miles use half a litre, that takes about 65 p off the saving (ill not go into wear and tear) over 30 years of work 50 weeks a year this means a saving of £1,275 over 30 years ... sounds a lot but
20 mins away - this assumes 40 minutes per week over 50 weeks is 2000 minutes, and over 30 years 60000 minutes. Now assume you are awake for 16 hours a day this equates to 62.5 days of free time - more than two months of awake time
so as the saying goes... which would you prefer £1,275 saving or 62.5 days of time
But it's still useful to know about price variation so that you can plan ahead. I regularly drive past several different petrol stations, and if I know that one of them is usually cheaper or usually more expensive then I choose to use or avoid it, or to decide that I'll fill up tomorrow when I'm going that way rather than today at a more expensive one.
And that'd be more useful built into satnav, so that if I know I have to fill up somewhere along my route then I can pick the cheapest place, since there's no real time cost to any of the options compared to each other.
It's interesting running the numbers though. e.g. if it only take 10 minutes to get cheaper fuel, how much cheaper does it need to be for your time to be worth more than the UK minimum wage (£12.21 for adults over 21)
based on my maths (from above calculations) it needs to be about 7p per litre cheaper to justify the extra 10 minutes and for your time to be worth more, per hour, than the minimum wage.
A 7p per litre difference does sound like the difference between local station and motorway prices though, and they probably will have factored in that opportunity cost of time...
Only 7p?
Motorway services have shocking price markups, way more than 7p. Most people don't realise this or are just too lazy to find something that isn't quite as convenient.
According to the live feed at https://www.rac.co.uk/drive/advice/fuel-watch/ I see:
Unleaded is 131.80p (UK wide) and 156.80p (Motorway Service Area).
Last time I drove into a motorway services and saw prices ~20p/litre higher I just drove through the petrol station and found a local garage to fill up at.