Is Driving to a Cheaper Petrol Station Actually Worth It? We Did the Maths

The assumption that costs UK drivers millions

Most of us operate on a simple rule: cheaper petrol = drive there. It feels like common sense. But it ignores one crucial thing — getting to that cheaper station uses fuel too. And that fuel costs money at whatever price you already have in the tank.

According to surveys, British drivers make an average of two dedicated trips to cheaper petrol stations per month. If even half of those trips aren't actually profitable, that's a lot of wasted miles across millions of cars.

The break-even calculation explained

Here's the core question: how much does the detour cost you, and how much do you save?

Let's work through a real example. You drive a fairly typical family car that does 40 MPG in real-world conditions. You're going to fill up 45 litres (roughly a full tank for most mid-size cars). The cheaper station is 5p per litre cheaper.

Your gross saving: 45 × 5p = £2.25.

Now the detour cost. Every mile you drive uses fuel. At 40 MPG, you consume roughly 0.57 litres per mile. At today's average UK pump price of around 136p/litre, each mile costs you approximately 77p in fuel. A 1-mile detour there and back is 2 miles total = around 80p.

So with a saving of £2.25, your break-even detour distance is roughly 2.8 miles each way— or 5.6 miles round trip. Drive further than that, and you've spent more on the detour than you've saved on the cheaper price.

Why your MPG changes everything

The 40 MPG example is fairly average, but the numbers shift dramatically based on your vehicle:

A 25 MPG SUV or van burns through fuel far faster. That same 5p/litre deal only breaks even at about 1.7 miles each way. If the cheaper station is across town, you're losing money.

A 55 MPG hybrid, on the other hand, uses much less fuel to get there. The break-even extends to around 4 miles each way. Hybrid drivers genuinely can afford to be pickier about where they fill up.

This is why a generic "is it worth it?" answer is meaningless without knowing your specific car. WorthThePump pulls your vehicle's real-world MPG from the official VCA dataset the moment you enter your number plate — no manual input needed.

When bigger price differences change the equation

Price differences of 5p/litre are common, but sometimes you'll spot a station that's 10p or even 15p per litre cheaper. These larger gaps do extend how far a detour can be justified.

At 10p/litre on 45 litres, your gross saving is £4.50. For our 40 MPG car, the break-even extends to 5.6 miles each way. That's a meaningful difference — but still not "worth a 15-minute drive across town" for most people.

If you're filling a large tank — say 70 litres in a van or 4x4 — the savings scale up and the break-even distance stretches further still. Fleet drivers and those with large-tank vehicles genuinely should be more selective about where they fill up.

The hidden cost nobody talks about: time

We've focused on pure fuel maths, but there's another cost: your time. A 5-minute detour might feel trivial, but if you're making that trip twice a week, that's over four hours a year spent driving to cheaper petrol stations — potentially for a net saving of zero.

WorthThePump doesn't currently put a monetary value on your time (everyone values it differently), but knowing the actual fuel saving is already a huge filter. If the numbers don't work out financially, they certainly don't work out when you factor in your time too.

Know before you go

The solution isn't to stop caring about petrol prices — far from it. Genuine savings are absolutely real, and over a year they add up significantly. The solution is to check the numbers before you start the engine.

Enter your number plate into WorthThePumpand we'll instantly show you every petrol station within your chosen radius, ranked by actual net saving after the detour cost. Green pins mean it's genuinely worth it. Red pins mean you'd be better off filling up where you are. No maths required on your part.