How far is it worth driving for cheaper fuel? The sum, with this morning's numbers

[jameswhitfield]

The car talk in the winter thread got me doing a sum I should have done years ago, so here it is with today's figures in case it saves anyone a wasted trip.

This morning the motorway average is 192.0p a litre against 173.9p on ordinary forecourts. That is a premium of 18.1p, or £9.05 on a 50 litre fill, and £10.90 against a supermarket. The 168 service areas that report prices are the dearest fuel in the country and have been all year: motorway fuel prices sit that far above the rest whatever the barrel does.

Now the cost of the detour. A car doing 40 mpg burns roughly 0.11 litres a mile, so at 173.9p you are spending about 20p a mile to go and fetch the cheaper fuel.

Put the two together and leaving the motorway buys you about 45 miles of round trip before the detour has eaten the whole saving. Nobody drives 45 miles for fuel, so coming off is almost always the right call, even for a junction or two of faffing.

Locally it turns over completely. Between two forecourts in the same town the gap is usually two or three pence. At 3p a litre you save £1.50 on a fill, and the break even is under eight miles there and back. Driving across town to save a penny is a hobby, not a saving, and it is worth knowing which one you are doing.

One caveat that applies to every price site, the one I check included. Stations are meant to report a change within half an hour, but plenty of entries are three or four days old, and a stale reading is a guide rather than a quote. Worth a glance at the timestamp before you commit to the drive.

[Peter]

I don’t chase fuel prices, as I don’t let the tank drop below half I can choose where and when to fill up,
and if I see fuel reasonable top up. I’ve not driven on a motorway for a few years now but I would only
buy fuel from a service station if there was no option, as motorway services get priority fuel deliveries.

[grenfell]

I normally use the local supermarket for my fuel . There's one other petrol station in the town that's normally a penny or two dearer. People complain about both of them on the local Facebook page. Closest after that is about four miles away and that either matches the supermarket or is a penny or two cheaper. I don't tend to think it's worth driving to it just to fill up but I do use it if I go past it to a job. I have a Costco card and they can be up to ten pence a litre cheaper but the nearest to me is about 20 miles away. It also entails something like a 20 minute wait in the queue. We do use it if we go there although seeing as we end up spending a fair wack at Costco filling up as well means quite an outlay even if we are saving. Though I tend to use my van most days for work the majority of my work is less than ten miles away so a thankful can last quite a while.

[GeraldTheBonzai]

Normally have a quick look on Waze. Tend to know which are the local expensive places.

[korolev]

I use an app called (unsurprisingly) Petrol Prices. It gives you the cheapest garages nearby ranked either by distance or price.

It varies enormously across the country, I filled up in Telford* this morning at £1.75/l. Here in Devon its 12p/litre cheaper at Trago Mills**. On the motorway we saw it was £1.95/l. As I sid to the Mrs "You'd have to be loaded, daft or desperate to pay that".

* Nice place, nice people.
** If you know, you know.

[GeraldTheBonzai]

Just drove back via the Cotswolds. Diesel 201.9p. unleaded 175.9p.........

[Peter]

There’s a Tesco petrol station 1/2 mile away from us but our 25yr old car runs rough on their E10,
there’s a BP station a little further away, car runs smoother and engine seams more responsive
and I think gives more MPG, so guess which I use, you get what you pay for.

[Arzosah]

The car talk in the winter thread got me doing a sum I should have done years ago, so here it is with today's figures in case it saves anyone a wasted trip.

This morning the motorway average is 192.0p a litre against 173.9p on ordinary forecourts. That is a premium of 18.1p, or £9.05 on a 50 litre fill, and £10.90 against a supermarket. The 168 service areas that report prices are the dearest fuel in the country and have been all year: motorway fuel prices sit that far above the rest whatever the barrel does.

Now the cost of the detour. A car doing 40 mpg burns roughly 0.11 litres a mile, so at 173.9p you are spending about 20p a mile to go and fetch the cheaper fuel.

Put the two together and leaving the motorway buys you about 45 miles of round trip before the detour has eaten the whole saving. Nobody drives 45 miles for fuel, so coming off is almost always the right call, even for a junction or two of faffing.

Locally it turns over completely. Between two forecourts in the same town the gap is usually two or three pence. At 3p a litre you save £1.50 on a fill, and the break even is under eight miles there and back. Driving across town to save a penny is a hobby, not a saving, and it is worth knowing which one you are doing.

One caveat that applies to every price site, the one I check included. Stations are meant to report a change within half an hour, but plenty of entries are three or four days old, and a stale reading is a guide rather than a quote. Worth a glance at the timestamp before you commit to the drive.

I really like this analysis - it sounds like it's a game of two halves, so to speak I don't drive long distances, but who knows when I might, it's still useful to know.

[jameswhitfield]

Thanks all, some good sense in here, and Arzosah, glad it was useful.

Peter, on the E10 point, it may not be the brand. Since 2021 the ordinary unleaded at Tesco and at BP is E10 at both. If the car runs better at the BP it could be that you are putting super in there, which is still E5 at most big stations. For a 25 year old car that is worth doing on purpose, and the gov.uk E10 checker will tell you whether yours is on the list.

korolev, any app is only as good as the prices the stations send in. They are meant to report within 30 minutes of a change, and some do: this week about 81% of Tesco prices were less than two days old, against 12% for Sainsbury's. So the cheapest one on the screen is sometimes just the one that has not updated. Worth a glance at when it was last reported before you drive to it.

grenfell, the Costco sums are the same as the motorway ones in reverse. Ten pence on 50 litres is £5, so a 40 mile round trip only pays if you were going anyway, which it sounds like you are.

[grenfell]

We went to Scotland over the weekend . Prices varied by quite a bit. On the motorway petrol was 199.9 a litre and we saw diesel at 219.9 but then we topped up in Gretna on the way back and paid 172.9 for petrol.