Forget what it says on the tin, these real-world economic numbers name the best gas guzzlers and the biggest gas guzzlers

• The most economical car is a hybrid Toyota crossover that gets 60.1 mpg
• The least efficient model tested by What Car? It manages just 21.17 mpg
• Based on current petrol prices, the difference in annual fuel bills is up to £1,100

With the price of petrol still above £1.50 a litre, and the country still in the grip of cost of living pressure, having an economical car with low fuel bills is crucial for some drivers.

The problem is that you can’t always rely on the miles per gallon (mpg) numbers that car manufacturers display in their showrooms, on their websites, and in their TV ads.

This is because the “official” tests to produce these numbers are performed in laboratories with unrealistic driving behavior.

However, which car? It launched its Real MPG database more than a decade ago to tell motorists which of the latest vehicles are the most and least efficient.

According to Consumer Headline, the most efficient model I’ve tested so far is a £25,000 Toyota crossover in showrooms today, which is £1,100 a year cheaper on fuel than the largest gas-guzzler I’ve reviewed.

The difference is that the driving methods used to calculate the figures are more representative of British motoring habits, with urban, rural and motorway sections with more aggressive acceleration and braking than used in official testing.

This provides miles per gallon numbers that motorists are likely to see when they are behind the wheel every day and driving as they normally would.

There is a separate “real range” test for electric cars, which means those tests are not included here.

While regular hybrids are tested as part of the Real MPG database, plug-in hybrids – or PHEVs – are not included because numbers for the latter vary widely depending on how far you travel and how much charge you have in the car. The beginning of your journey.

With this in mind, which car? It revealed which of the hundreds of models I’ve tested in recent years got the highest and lowest mpg results.

The best performing car tested was the Toyota Yaris Cross 1.5 Hybrid, which recorded a real mpg rating of 60.1mpg, which (using current fuel prices) works out at just 11.2p of petrol per mile.

In second place were the Toyota Yaris 1.5 Hybrid and the Suzuki Ignis 1.2 Dualjet Hybrid, both of which managed to achieve 59.9 mpg.

By contrast, the worst-performing car tested was the high-performance Audi S8.

Since it’s powered by a 4.0-litre twin-turbocharged V8 petrol engine, it’s no surprise to see that it achieved 21.7mpg under real MPG conditions – at an average fuel cost of 31p per mile.

The Audi S8 was followed by the Alfa Romeo Giulia Quadrifoglio – a contender in the hot hatch segment with a 2.9-litre twin-turbo V6 – achieving 23.5 mpg.

Lexus The LC Cabriolet — a naturally aspirated gasoline V8, not the hybrid sports car — comes in third from bottom with a score of 24.2 mpg.

Looking at the average real world mpg across all 371 cars tested by What Car? It is 42.3 mpg, which represents a much greater fuel expense.

Below we’ve listed the best and worst performing cars in Real MPG measurements, although all cars are still available in showrooms and can only be purchased second hand today.

Using the latest annual mileage figures from the UK Department for Transport – which show the average mileage for petrol and diesel cars is 5,550 miles per year – combined with fuel pricing data, the annual fuel cost of an Audi S8 is £1,722.32, while The Toyota Yaris Cross Hybrid costs just £621.87.

Even within vehicle categories, making the right decision can result in significant savings.

In the popular family SUV market, for example, the gap between the best and worst performers was more than 28.1mpg, meaning drivers could save £657 in fuel costs each year by choosing a used Renault Kadjar diesel over a petrol Volvo XC40.

Steve Huntingford, what car? The editor said: “There is often a huge discrepancy between real-world driving efficiency and the official government figures that carmakers are required to publish.

However, our real MPG tests give car buyers realistic numbers to help inform their purchases.

“As our figures show, by choosing carefully, it is possible to save a lot of money in the long term, especially with fuel prices as high as they are today.”