🚗 Is Supermarket Petrol Bad for Your Car? Resolvo Explains

Your mate swears Asda petrol ruined his engine. Your dad only uses Shell "because it's better quality." Your colleague says Tesco fuel is watered down. Your wallet is crying.

Who's actually right?

With supermarket fuel typically 7-10p per litre cheaper than branded stations, this question matters. The difference between filling up at Tesco (133p/L) versus Shell (142p/L) is £4.50 per tank, or £234 per year for an average driver.

So is that saving a smart move or slow engine damage? We spoke to mechanics, checked the regulations, and dug into the science. Here's the truth.

👉 Find the cheapest petrol or diesel prices near you

💷 The Short Answer: No, Supermarket Fuel Is NOT Bad for Your Car

UK fuel regulations are strict. All petrol and diesel sold in the UK — whether from Tesco, Shell, or a random independent station — must meet exactly the same British and European standards:

• Petrol: BS EN 228 and E10 specification

• Diesel: BS EN 590 specification

These standards cover:

• Octane rating (RON 95 minimum for regular unleaded)

• Sulphur content (max 10ppm)

• Detergent additives (minimum required levels)

• Density and volatility

• Contaminant limits

If a fuel doesn't meet these standards, it cannot legally be sold in the UK. Full stop.

So when you fill up at Asda, you're getting fuel that meets exactly the same regulatory baseline as BP, Esso, or Shell regular unleaded.

🔬 But What About "Quality" and "Additives"?

This is where it gets nuanced.

The Base Fuel Is Identical

Supermarkets and branded stations often buy from the same refineries. The tanker that delivers to Tesco in the morning might deliver to Shell in the afternoon. Same fuel, different branding.

The Difference: Additive Packages

Branded stations (Shell, BP, Esso) add extra detergents and cleaning additives beyond the legal minimum. These proprietary blends are marketed as:

• Shell V-Power

• BP Ultimate

• Esso Synergy Supreme+

What do these additives actually do?

• Help keep fuel injectors and intake valves cleaner

• Reduce carbon deposits over time

• May improve fuel economy by 1-2% (manufacturer claims)

The catch: These premium fuels cost 25-30p per litre more. That's £12.50-15 extra per tank.

🔧 Why Supermarket Fuel Gets a Bad Reputation (And Why It's Wrong)

The "supermarket fuel is bad" myth persists for a few reasons:

Reason 1: Confirmation Bias

Someone fills up at Asda, their car develops an unrelated problem a week later, and they blame the fuel. Meanwhile, thousands of other drivers using the same fuel have zero issues.

If supermarket fuel genuinely caused engine problems, we'd see:

• Mass recalls and scandals

• Mechanics refusing to recommend it

• Manufacturer warnings

• Legal action

None of this exists. Because the fuel is fine.

Reason 2: The 2007 Tesco Contamination Incident

In 2007, a batch of Tesco fuel was contaminated with silicon, affecting around 250 cars. This made national news and became the foundation for the "supermarket fuel is bad" myth.

But context matters:

• This was nearly 20 years ago

• It affected ONE batch from ONE supplier

• Tesco compensated all affected customers

• Contamination can happen to ANY fuel supplier (Shell had issues in Aberdeen in 2017, BP in Edinburgh in 2019)

• Modern testing catches these incidents faster

Reason 3: Branded Fuel Marketing

Shell, BP, and Esso spend millions on marketing their premium fuels. Part of that strategy involves implying (without directly stating) that supermarket fuel is inferior.

This benefits them in two ways:

• Keeps people buying expensive premium fuel

• Creates doubt about cheaper alternatives

The reality: All UK fuel meets identical baseline standards. The difference is additives, not quality.

Reason 4: The Placebo Effect

People who switch to branded fuel and "feel" a difference are experiencing psychological effects, not mechanical ones. Blind tests consistently show drivers cannot tell the difference between supermarket and branded regular unleaded.

What Actually Causes Fuel-Related Problems

When cars DO have fuel system issues, it's usually:

• Old/dirty fuel filters (maintenance issue)

• Contaminated fuel tanks (any fuel supplier)

• Wrong fuel type (petrol in diesel or vice versa)

• Aged fuel in rarely-driven cars (sitting for months)

None of these are specific to supermarket fuel.

🚗 What Car Manufacturers Actually Say

We checked owner's manuals for the UK's most popular cars:

Key finding: 95 RON (standard supermarket unleaded) is the minimum for virtually every car. Some German cars recommend 98 RON but don't require it.

💡 When Premium Fuel Actually Matters

There are a few specific scenarios where premium fuel makes sense:

1. Manufacturer REQUIRES 98+ RON

Some high-performance cars explicitly require super unleaded:

• Porsche 911 Turbo

• BMW M3/M4

• Mercedes-AMG models

• Some Audi RS models

Check your manual. If it says "requires" or "must use" 98 RON, then use it. If it says "recommended" or "for optimal performance," standard fuel is fine.

2. High-Performance Driving

If you're regularly:

• Track driving

• Towing heavy loads

• Driving in extreme conditions

Premium fuel's higher octane can prevent engine knock under high stress.

3. Very Old Cars (Pre-2000)

Older engines designed before modern fuel standards may benefit from premium fuel's extra additives. But even this is debatable.

For Everyone Else?

You're wasting £12-15 per tank for negligible benefit.

🔍 The Additives Debate: Do They Really Help?

Premium fuels advertise proprietary additive packages. Let's break down the claims vs reality:

Claim: "Cleans Your Engine"

Reality: All UK fuel contains detergent additives (required by law). Premium has more, but the baseline is already effective for modern engines.

Independent testing: Some studies show 1-2% improvement in fuel economy after using premium fuel for several tanks. But that 1-2% gain doesn't offset the 20% price premium.

Claim: "Prevents Carbon Build-Up"

Reality: Modern engines with direct injection are prone to carbon build-up regardless of fuel type. Premium fuel helps slightly, but doesn't eliminate the issue.

Mechanic perspective: "If you want to prevent carbon build-up, drive your car properly — don't just do short trips, get it up to temperature, and use higher RPMs occasionally. That's more effective than expensive fuel."

Claim: "Better Performance"

Reality: Only noticeable in high-performance engines designed to exploit higher octane. Your Vauxhall Corsa won't feel any different.

🧪 The Water/Contamination Myth

The myth: "Supermarket fuel is watered down or contaminated more often."

The reality:

• All fuel suppliers face the same contamination risks

• Supermarkets have high turnover = fresher fuel

• Contamination incidents are extremely rare and affect all fuel types equally

• When contamination happens, it makes national news (Shell Aberdeen 2017, BP Edinburgh 2019) — not exclusive to supermarkets

Fuel testing is mandatory: Random samples are tested regularly. Contaminated fuel is caught before it reaches consumers in almost all cases.

💳 What About Loyalty Cards and Fuel Rewards?

If you're debating supermarket vs branded fuel, factor in loyalty schemes:

Tesco Clubcard

• 1 point per £1 on fuel = 1p value

• Effective discount: 1p/L

• Makes Tesco even cheaper

Sainsbury's Nectar

• 1 point per £1 = 0.5p value

• Regular 5p/L off events

• Check app before filling

Shell Go+

• 1 point per litre

• Redeem for fuel discounts

• Still doesn't overcome 10p price premium

BP Plus

• Points on fuel and shop purchases

• Similar to Shell — doesn't offset premium

Verdict: Supermarket loyalty schemes add value. Branded schemes don't overcome the base price difference.

🔍 FAQs About Supermarket Fuel

Q: Will supermarket fuel void my warranty? A: No. As long as it meets the manufacturer's specified RON rating (usually 95), your warranty is valid.

Q: Why do some people swear their car runs better on branded fuel? A: Placebo effect, confirmation bias, or they coincidentally fixed another issue (spark plugs, air filter) when they switched fuel. Blind tests show no performance difference.

Q: Is supermarket diesel different too? A: Same story. All diesel must meet EN 590. Supermarket diesel is not lower quality.

Q: What about supermarket premium (Tesco Momentum, Sainsbury's Super)? A: These are 99 RON fuels with added additives, comparable to Shell V-Power or BP Ultimate. Still cheaper than branded premium.

Q: Can I mix supermarket and branded fuel? A: Yes, they're 100% compatible. Your car doesn't care.

Q: Should I use fuel injector cleaner additives? A: If you're concerned, use a bottle of injector cleaner once a year (£5-10). Far cheaper than premium fuel year-round.

Q: Does E10 petrol affect this? A: E10 (10% ethanol) is now standard in the UK. All suppliers use it. Same standards apply whether supermarket or branded.

Q: What if I accidentally use the wrong fuel? A: That's a different issue (petrol in diesel or vice versa). Call recovery immediately, don't start the engine. This risk is equal regardless of where you buy.

🧾 Final Thoughts

The "supermarket fuel is bad" myth has cost UK drivers millions over the years. It's marketing genius by branded stations — make you doubt the cheaper option so you pay a premium for identical baseline quality.

Here's the truth:

• Supermarket fuel meets the same legal standards as branded

• Your car manual specifies the minimum RON — usually 95 (supermarket regular)

• 95% of UK cars see zero benefit from premium fuel

• The £200-350 you save annually by using supermarket fuel is real money

Your car doesn't care whether the fuel comes from Tesco or Shell. But your wallet does.

Stop wasting money on expensive fuel myths. Start using supermarket fuel and spend the savings on things that actually matter — proper servicing, good tyres, or just keeping the money in your pocket.

👉 Find the cheapest petrol or diesel prices near you

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