Guide

Is supermarket fuel worse than branded fuel?

What the law says every litre must meet, what the brands say they add, and how much less the supermarkets charge.

By Forecourt Prices Published Updated

The short answer

Not in law. Every litre of petrol and diesel sold at a filling station must meet the same standard, whoever runs it[1].

In Great Britain, petrol must be at least 95 octane, and diesel must have a cetane number of at least 51[2].

Brands add their own additives and say what they do. We quote them below. We have not tested any fuel.

Supermarket petrol (E10) 170.0p

Major brands 171.8p

Petrol gap 1.8p

less at supermarkets, 99p a 55-litre fill

Supermarket diesel (B7) 195.9p

Major brands 198.8p

Diesel gap 2.9p

less at supermarkets, £1.60 a 55-litre fill

On our latest figures, supermarket petrol (E10) averages 170.0p a litre, 1.8p less than the major brands' 171.8p. On a 55-litre fill that is 99p less.

On our latest figures, supermarket diesel (B7) averages 195.9p a litre, 2.9p less than the major brands' 198.8p. On a 55-litre fill that is £1.60 less.

These averages come from 1,409 supermarket and 4,601 major-brand forecourts for petrol, and 1,265 and 4,155 for diesel, in our price data, not counting motorway services. We update it every 15 minutes.

The supermarkets are Tesco, Morrisons, Sainsbury's and Asda. The major brands are Esso, BP, Shell and 12 more. Each figure averages forecourts, not brands.

Most of the prices behind these averages are more than 3 days old.

Updated 6:47am on 2 November.

Compare every brand on our fuel prices by brand page.

What every litre must meet

The Motor Fuel (Composition and Content) Regulations 1999 forbid selling petrol or diesel at a filling station if it misses the set specification[1].

Since 2021 that specification has been a table in the regulations. It applies in Great Britain, and its test methods are those of BS EN 228 for petrol and BS EN 590 for diesel[2].

The main limits for petrol and diesel sold in Great Britain, from Schedule AA1 of the regulations.
Fuel Measure Legal limit
Petrol Research octane number (RON) At least 95
Petrol Motor octane number (MON) At least 85
Petrol Ethanol Up to 10% by volume
Petrol Benzene Up to 1% by volume
Petrol Sulphur Up to 10 mg/kg
Diesel Cetane number At least 51
Diesel Biodiesel (FAME) Up to 7% by volume
Diesel Density at 15°C Up to 845 kg/m³
Diesel Sulphur Up to 10 mg/kg

Source: the 2021 amending regulations, Schedule AA1[2].

The table covers what the fuel is made of. It doesn't list detergents[2].

GOV.UK says standard grade (95 octane) petrol became E10 in Great Britain in September 2021. E10 holds up to 10% renewable ethanol[3].

Stations that sell two grades of petrol stock E10 (95 octane) and E5 (97+ octane), the "super" grade, GOV.UK says[3].

We have not checked Northern Ireland's own fuel rules, so the figures above are for Great Britain.

E10 vs E5: what's the difference, and is E5 worth the extra?

Where supermarket fuel comes from

The CMA studied the UK road fuel market and published its final report in July 2023. Its figures on who supplies whom are for 2022[4].

Retailers buy from independent wholesalers, or straight from refiners and importers that have a wholesale arm, the CMA said[4].

It described two kinds of supply. Unbranded supply "typically covers the supply of fuel only", and retailers sell it "under their own brand"[4].

The CMA said unbranded supply goes "primarily to supermarkets"[4].

In 2022, it found, Greenergy was the largest wholesale supplier, followed by Esso, BP, Shell and Valero. Its table notes that Greenergy and Petroineos "do not make branded sales"[4].

In 2022, the CMA also found that "Shell is not a supplier to supermarkets" and "BP is not a significant supplier to supermarkets"[4].

Read together, those findings put supermarkets in the same wholesale market as the brands[4]. Both sell to the same legal standard[1].

The CMA's findings don't say whose fuel any one forecourt sells.

Asda says "our fuel conforms to the same standards and comes from the same refineries as the branded oil major petrol stations"[5].

That is Asda's claim about refineries. The CMA's findings above are about who supplies supermarkets.

What the brands say they add

In the brands' own words. We have not tested any fuel.

Shell

Shell says "Shell V-Power unleaded contains three times more cleaning and protection molecules than our regular fuel"[6].

Its footnote says that is compared with Shell's FuelSave Unleaded, and "No guarantees provided"[6].

For V-Power Diesel, Shell claims "60% more cleaning and protection molecules" than its FuelSave Diesel[7].

BP

BP says its Ultimate fuels "are specially designed to remove dirt and protect against its build up in both petrol and diesel engines"[8].

BP claims "up to 375 more miles per year". Its footnote bases this on 6,400 miles a year, and compares Ultimate Unleaded with 95 octane petrol[8].

Its footnote adds "For Ultimate Diesel based on engines tested in dirty vs. cleaned condition. Benefits may vary due to factors including vehicle, driving style and driving conditions."[8]

Esso

Esso says "when we tested Synergy diesel on everyday cars it helped improve fuel economy by an average of 1.8%"[9].

Its footnote says the test was on used diesel vehicles over 4,000 km, and that "Benefits may vary"[9].

Esso also says "Our Synergy Supreme+ Diesel has double the detergent additive than our regular diesel."[9]

Texaco

Texaco says its Premium Unleaded 95 "contains a detergent additive to help keep fuel injectors clean"[10].

It says "Texaco Diesel contains a detergent additive to help keep injectors clean"[10].

JET

JET says "JET ULTRA Premium Fuels contains enhanced detergent levels designed to help remove deposits and help keep key engine parts cleaner over time."[11]

Costco

Costco says "Every grade of Kirkland Signature™ Fuel contains deposit control additive that keeps your engine protected and running like new."[12]

It also says "Variations in deposit control additive formulations are the main difference between brands of fuel." That is Costco's view[12].

Asda

Asda says "Asda fuel includes specially formulated additives and detergents, which keep your engine clean and improve engine efficiency."[5]

Tesco

Tesco says "Our Momentum 99 petrol contains a special blend of additives to help keep a car's fuel system clean and working at its best."[13]

We found no page from Sainsbury's or Morrisons about what goes into their fuel.

The law sets the same floor for all of these fuels[2]. We can't tell you whether any brand's additives make a difference in your car.

How much cheaper is supermarket fuel?

How much less a litre supermarket petrol and diesel cost than the major brands' each day since 5 March 2026, in pence.

How much less a litre supermarket petrol and diesel cost than the major brands' each day since 5 March 2026, in pence. The sentences under the chart say what it shows.
  • On 1 November, supermarket petrol was 1.9p a litre cheaper than at the major brands, and supermarket diesel 3.0p a litre cheaper.
  • Since 5 March 2026, the gap has averaged 3.2p for petrol and 4.1p for diesel.
  • The petrol gap was widest at 7.0p on 27 March, and narrowest at 1.5p on 7 October.
  • The diesel gap was widest at 10.7p on 26 March, and narrowest at 0.9p on 4 April.

We leave out 1 day. On it, a brand was missing from our figures, or a change in one brand's forecourt count moved a gap by more than 0.5p.

Figures to 1 November 2026.

Daily brand averages from our price data, each group weighted by its forecourts, not counting motorway services.

Between 5 March and 1 November, Asda had the cheapest supermarket petrol on 114 days, Tesco on 60, Sainsbury's on 58 and Morrisons on 41.

On 26 of those 241 days two or more shared the lowest petrol price, and each is counted.

For diesel, Tesco had the cheapest supermarket diesel on 94 days, Morrisons on 68, Sainsbury's on 62 and Asda on 36.

On 19 of those 241 days two or more shared the lowest diesel price, and each is counted.

Asda has the cheapest petrol and diesel of the big supermarkets, at 169.6p and 195.4p.

Most of the prices behind these averages are more than 3 days old.

See which supermarket is cheapest on our fuel prices by brand page.

Some other brands' petrol averages less than the supermarkets': Costco (members only), and in Northern Ireland, Go, Solo, Emo, Maxol and Circle K. Most of the prices behind these averages are more than 3 days old.

In 2023 the CMA found that the gap between supermarkets and other retailers "has remained constant at around 4-6ppl since 2017". That held outside "brief periods of disruption associated with Covid and Russia-Ukraine-related supply issues"[4].

The exception was diesel against "dealers". There, the CMA said, supermarkets had been "on average only around 2ppl cheaper during 2023"[4].

The CMA also found Asda was the cheapest supermarket in 89% of weeks for petrol from 2019 to 2021. From January 2022 to May 2023 it was cheapest in 76%[4].

The CMA compared supermarkets with every other retailer, so its figures are measured differently from ours.

Which petrol station has the best fuel?

We can't say any fuel is the best. We have not tested any, and every forecourt sells to the same legal floor[2].

What we can show is each brand's premium grade, what it calls it and what it charges. The table has each brand's prices.

Each brand's average price for each fuel at its own forecourts, not counting motorway services, cheapest petrol first, with its own name for a premium grade.

Brand averages from our price data, from each brand's forecourts away from motorway services.

Each brand's average price for each fuel at its own forecourts, not counting motorway services, cheapest petrol first, with its own name for a premium grade.
Brand Petrol (E10) Super unleaded Diesel (B7) Premium diesel
Costco Members only 164.1p, mostly from older prices 174.6p Premium Unleaded 97 189.5p, mostly from older prices No figure
Asda 169.6p, mostly from older prices No figure 195.4p, mostly from older prices No figure
Morrisons 169.8p, mostly from older prices No figure 196.5p, mostly from older prices 206.4p, mostly from older prices
Sainsbury's 169.8p, mostly from older prices 181.8p, mostly from older prices 196.2p, mostly from older prices No figure
JET 169.9p, mostly from older prices No figure 197.5p, mostly from older prices No figure
Texaco 169.9p, mostly from older prices 186.2p, mostly from older prices Texaco Supreme Unleaded 196.8p, mostly from older prices 212.0p, mostly from older prices Texaco Supreme Diesel
Tesco 170.6p, mostly from older prices 181.3p, mostly from older prices Momentum 99 195.5p, mostly from older prices No figure
Esso 171.7p, mostly from older prices No figure 199.3p, mostly from older prices No figure
BP 172.6p, mostly from older prices 191.8p, mostly from older prices BP Ultimate Unleaded 199.6p, mostly from older prices 218.2p, mostly from older prices BP Ultimate Diesel
Shell 174.2p, mostly from older prices 195.4p, mostly from older prices Shell V-Power 200.3p, mostly from older prices 222.8p, mostly from older prices Shell V-Power Diesel

Super unleaded costs from 10.7p a litre more than the same brand's petrol, at Tesco, to 21.2p more, at Shell. Most of the prices behind these averages are more than 3 days old.

Premium diesel costs from 9.9p a litre more than the same brand's diesel, at Morrisons, to 22.5p more, at Shell. Most of the prices behind these averages are more than 3 days old.

Costco sells one diesel, which it calls Premium Diesel, so its diesel figure is for that fuel[12].

Figures marked † are mostly from prices over 3 days old.

Brand averages updated 6:47am on 2 November.

Super unleaded and premium diesel at supermarkets

GOV.UK calls E5 the "super" grade, at 97 octane or more[3].

Tesco says most of its petrol stations in England, Scotland and Wales stock Momentum 99[13].

It says it doesn't currently have a supply terminal in Northern Ireland that can produce its high octane base fuel[13].

Of the big supermarkets, Tesco and Sainsbury's have a super unleaded price in our data, at 396 and 291 forecourts respectively. Morrisons and Asda superstores have none.

Tesco Momentum 99 averages 181.3p a litre and Sainsbury's super unleaded 181.8p. Most of the prices behind these averages are more than 3 days old.

At the major brands, premium petrol runs from 186.2p for Texaco Supreme Unleaded to 195.4p for Shell V-Power. Most of the prices behind these averages are more than 3 days old.

Morrisons is the only big supermarket with a premium diesel price in our data, at 81 forecourts. Tesco, Sainsbury's and Asda superstores have none.

Morrisons' super diesel averages 206.4p a litre. Most of the prices behind the Morrisons' super diesel average are more than 3 days old.

We have found no name for Morrisons' premium diesel, so we call it super diesel.

At the major brands, premium diesel runs from 212.0p for Texaco Supreme Diesel to 222.8p for Shell V-Power Diesel. Most of the prices behind these averages are more than 3 days old.

Each brand's average from our price data, at its own forecourts, not counting motorway services.

Why supermarket fuel is cheaper

In 2023 the CMA found that supermarkets "remain, on average, cheaper than other types of retailer"[4].

The CMA's report put supermarkets at 43% of road fuel sold but only 18% of forecourts, on December 2022 figures[4].

In 2022 a supermarket forecourt sold 10.6 million litres on average, the CMA said. An oil company site sold 4.8 million, and an independent 2.5 million[4].

The CMA found supermarkets' average fuel margin rose from 4.6p a litre in 2019 to 10.8p in 2022[4].

In its 2023 study, supermarkets told the CMA the "halo effect" had declined. That is the idea that cheap fuel brings shoppers into the store[4].

The CMA judged the halo effect by its size as "estimated in supermarkets' own internal documents". In 2023 it said that size "is nowhere near large enough to account for the scale of margin increase we have seen on fuel"[4].

In August 2026 the CMA said: "Non-supermarket retailers also remain consistently more expensive relative to supermarkets."[14]

For June 2026, it put supermarket margins at 10.4p a litre across both fuels, against 12.0p for other retailers[14].

Common questions about supermarket fuel

Is supermarket fuel inferior?

Not in law. Every litre sold at a filling station must meet the same standard, whoever runs it[1]. In Great Britain that means at least 95 octane for petrol, and a cetane number of at least 51 for diesel[2]. We have not tested any fuel.

Is BP diesel better than Tesco diesel?

Both must meet the same legal standard, with a cetane number of at least 51 and up to 7% biodiesel[2]. BP makes claims for its Ultimate fuels, quoted above[8]. We have not tested either fuel. On our latest figures, Tesco diesel averages 195.5p a litre, 4.1p less than BP diesel at 199.6p. Most of the prices behind these averages are more than 3 days old.

Is Shell petrol better than supermarket petrol?

Shell says V-Power unleaded has "three times more cleaning and protection molecules than our regular fuel", meaning its FuelSave Unleaded[6]. Both must meet the same legal standard[2]. We have not tested either. On our latest figures, Shell petrol averages 174.2p a litre, 4.2p more than supermarket petrol at 170.0p. Most of the prices behind these averages are more than 3 days old.

Which supermarket has the cheapest petrol?

Asda has the cheapest petrol and diesel of the big supermarkets, at 169.6p and 195.4p. Most of the prices behind these averages are more than 3 days old. Between 5 March and 1 November, Asda had the cheapest supermarket petrol on 114 days, Tesco on 60, Sainsbury's on 58 and Morrisons on 41. Compare supermarket prices by brand.

Why is supermarket fuel cheaper?

The CMA found in 2023 that a supermarket forecourt sold 10.6 million litres in 2022, against 4.8 million at an oil company site[4]. It also found supermarkets' fuel margins rose from 2019 to 2022[4].

What is the difference between unleaded and super unleaded?

Standard unleaded is E10: 95 octane, with up to 10% renewable ethanol. Super unleaded is E5, at 97 octane or more[3]. E10 vs E5: is super unleaded worth the extra?.

Do supermarkets sell super unleaded?

Of the big supermarkets, Tesco and Sainsbury's have a super unleaded price in our data, at 396 and 291 forecourts respectively. Morrisons and Asda superstores have none.

What happens if I put 91 instead of 95?

Petrol sold at forecourts in Great Britain must be at least 95 octane, so 91 octane isn't on sale there[2]. Your car's handbook gives the grade it needs.

Which petrol is ethanol free?

Not standard unleaded: the law says 95 octane petrol must hold at least 5.5% ethanol[2]. Super unleaded is sold as E5, with no more than 5% renewable ethanol, GOV.UK says[3].

Sources and method

  1. legislation.gov.uk: The Motor Fuel (Composition and Content) Regulations 1999, checked 15 October 2026.
  2. legislation.gov.uk: The Motor Fuel (Composition and Content) and the Biofuel (Labelling) (Amendment) (No. 2) Regulations 2021, checked 15 October 2026.
  3. GOV.UK: E10 petrol explained, checked 13 October 2026.
  4. GOV.UK (CMA): Road fuel market study, final report, checked 15 October 2026.
  5. Asda: Asda Petrol Stations, checked 15 October 2026.
  6. Shell UK: Shell V-Power unleaded, checked 15 October 2026.
  7. Shell UK: Shell V-Power Diesel, checked 15 October 2026.
  8. bp UK: bp Ultimate fuels with ACTIVE technology, checked 15 October 2026.
  9. Esso UK: Synergy Fuels, checked 15 October 2026.
  10. Texaco UK: Our motor fuels, checked 15 October 2026.
  11. JET UK: JET ULTRA, checked 15 October 2026.
  12. Costco UK: Fuel Q&A, checked 15 October 2026.
  13. Tesco: Tesco Momentum 99, checked 15 October 2026.
  14. GOV.UK (CMA): Enhanced road fuel monitoring report: August 2026, checked 15 October 2026.

Our figures: each brand's average is over its forecourts' latest prices reported in the last 30 days, away from motorway services, leaving out prices far from what the rest of the UK charges. Each group's figure weights its brands by their forecourts. How we work out the figures