If you need to drive a car in the UK, you probably need to get an app call "Petrol Price", so that you can see the petrol price of the station nearby. 

Some said that Costco's petrol is the cheapest, so, is it worth it to register as a member, or drive to Costco just for gassing up? 

The calculation behind involves lots of factors, but I will use 1 Apr 2023's data to do a simple calculation here:

The photo above was the petrol that I filled up for my car (approximately half of the tank), the price was reasonable among the most station:

  • 146.9p per Litre
  • 23.92L = £35.14
If I gas up in Costco?
  • 138.9p per Litre
  • 23.92L = £33.22
Difference: £1.92

Well, not worth it to drive there just for gassing up...