E5, E10, B7, premium — what they all mean

Walk onto any UK forecourt and you'll see four nozzles: E10, E5, B7 and (sometimes) a premium diesel. Plus two or three proprietary names — Shell V-Power, BP Ultimate, Tesco Momentum. All of them fit one of these four standards.

E10 — standard unleaded

E10 has been the UK's default unleaded since September 2021. The "10" is the maximum percentage of bioethanol in the blend; the rest is regular 95-octane petrol. Switching to E10 cuts CO₂ emissions by roughly two percent over the lifetime of the fuel because the ethanol is renewable.

Almost every petrol car built since 2011 runs on E10 fine. If yours is older, GOV.UK's E10 compatibility checker will tell you in two clicks whether to use E5 instead.

E5 — "super" or premium unleaded

E5 is up to five percent ethanol and a higher octane (97–99 rather than 95). On the forecourt it's the more expensive green pump. There are two reasons to use it:

• Your car is on the GOV.UK list of vehicles that need it — mostly cars built before 2011, plus a handful of high-output modern engines.
• Your car is tuned for higher octane (look for "95 RON minimum, 98 RON recommended" in the manual). For most modern cars the manufacturer says E10 is fine.

B7 — standard diesel

B7 is up to seven percent biodiesel mixed into regular fossil diesel. Practically every car-grade diesel sold in the UK has been B7 for over a decade — you don't need to think about it unless you have a 1990s Mercedes that's been converted to run on something exotic.

Premium diesel

Premium diesel — V-Power Diesel, BP Ultimate Diesel, etc. — is the same B7 base with a stronger detergent additive package. On a normal car driven normally, the fuel-economy difference is within the noise. If your engine has a known sensitivity to deposit build-up (mostly common-rail diesels with a long history of short trips), running a tank of premium every few thousand miles is reasonable preventive maintenance. Doing it every fill-up rarely pays back at the pump.

What the brand additives actually do

Every major UK retailer adds a detergent package to its fuel — Shell's "FuelSave", BP's "ACTIVE", and so on. They are real and they are measurable, but the differences are small. The difference between two retailers' E10 prices on the same street is usually larger than the efficiency difference between their additive packs.