When you’re looking for guidance on a new or used car, how do you decide which information to trust? Car reviews, consumer surveys, research data? Where do you find all the right information, and then work out which is relevant to your needs and which is not that important?
There are tens of thousands of UK car reviews on the internet, from dozens of decent automotive websites (and plenty of reviews from sites you shouldn’t really rely on).
There’s also a lot of crucial data around safety, running costs, reliability and environmental impact. But which reports are trustworthy and which have specific agendas?
So how do you decide whose opinion to believe when you’re looking for a new car? Is Auto Express better than Autocar? How does the Telegraph compare to the Sunday Times? Or what about The Car Expert and Honest John? All of their reviews are written by experienced journalists, but they’re still all human beings with their own preferences and biases.
Not only that, but every website has its own way of measuring and scoring cars. If you’re only relying on one source, you’re not getting the full picture.
Fortunately, we’re here to help with our unique Expert Rating Index. We pull millions of data points together to give you the most detailed analysis possible of every new car on sale – and hundreds of previous models as well.
It’s no understatement to say that this is now the gold standard for rating and ranking new cars in the UK, and the only system of its kind anywhere in the world.
What is an Expert Rating?
The Expert Rating Index is something that The Car Expert has been developing and refining for the last six years. In January 2024 we launched our third-generation Index, which is an enormous leap forward in presenting crucial car buying guidance to UK car buyers.
Each new car on sale in the UK has a New Car Expert Rating. This is created by pulling in thousands of individual data points, covering different criteria for rating and ranking that car against every other car on the market. We gather data from new car reviews, safety testing, environmental testing, reliability records and running cost reports – all from trusted UK and European sources that assess cars sold here in the UK.
Using sophisticated algorithms, we convert these thousands of data points to scores for media reviews, safety, environmental performance, reliability and running costs – with more categories and more data sources coming soon.
These category scores are then fed into separate New Car and Used Car Expert Ratings, which specifically address the different priorities of new and used car buyers.
Expert Ratings, and the category ratings, are scored using our new report card format, presenting a clear and easy-to-understand scorecard for every car. We also include percentage scores alongside the A-F grading for readers who want more detail. We explain each category in more detail below.
Expert Rating categories
Media Rating
In previous generations of the Expert Rating Index, a car’s overall Expert Rating was made up exclusively of media review scores. This is now called the Media Rating, and is only one part of the calculations used for our new Expert Ratings.
The Media Rating for a car is an aggregated rating, made up of a number of individual review scores from up to 35 different sources. This can be as few as 10 reviews and, in some cases, is more than 60. Some car manufacturers limit the number of media titles invited to review their cars (usually luxury and exotic car brands), while others encourage reviews of every version of every model in their ranges.
What’s an aggregated rating?
Rather than relying on one source, we use reviews from up to 35 different media titles and then feed all of those reviews into a special algorithm, using what’s called a ‘weighted average’ to provide our Media Rating. We also calculate different Media Ratings for new and used cars.
The world’s most famous review aggregator website is Rotten Tomatoes, which compiles reviews for movies and TV shows. It then rates them on the number of positive reviews vs negative reviews, but there are many different methods of aggregating scores.
The Car Expert is the world’s only website to successfully apply review aggregating to new car reviews. Our system uses a weighted average of all the reviews of a particular car published by the 35 sites we include in our index. This is a similar process to sites like Metacritic (another film/TV/music review aggregator site), although we have our own proprietary algorithms developed specifically for new and used car reviews.
A weighted average is more complicated than a straight average because there are additional factors we take into consideration.
We factor in the age of each review for new cars, so that newer reviews carry more weight than older reviews. For used cars, we don’t factor reviews by age.
The Media Rating also breaks down the complex web of different scoring systems that different websites use in their reviews. A score of 7 out of 10 from one site might be an above average score from one site, a fairly average score from another site and below average from yet another site. So how is the average car buyer supposed to know which site to trust? The Media Rating pulls all that data together and makes thousands of calculations to produce an updated score – the only number that you can trust.
This rating alone took us us a couple of years to develop and refine, but the huge leap forward of our third-generation Index means it’s now only one part of the overall Expert Rating score.
What about car reviews that don’t provide a score?
Some titles review a lot of cars but they don’t provide scores (like the Daily Mail and the Sun). Other titles won’t score reviews for a short test and will only score vehicles on longer reviews. These reviews are still added to the database so you can find them and read them, but they don’t count towards the Expert Rating score.
Unlike some aggregator sites (Metacritic is one example), we don’t manually alter scores up or down, or create scores for unscored reviews. That works for their system, but we don’t think it’s the right solution for us. Occasionally, however, we may include a review but not its score if we think that it is not a fair representation. This decision is made solely by our editor.
Safety Rating
Our Safety Rating score is based on Euro NCAP testing results, using all of Euro NCAP’s testing categories rather than just the headline score.
This includes a complete breakdown of scores for adults, children, pedestrians and assist systems, so you can see the information that matters most to you. We also highlight any scores that have expired.
Euro NCAP scores expire after six or seven years, as the scoring criteria gets tougher each year and cars that were tested several years ago can no longer be guaranteed of maintaining their initial score. A car may be re-tested if it’s still on sale, although this doesn’t always happen.
We also take age into account, as Euro NCAP testing gets tougher almost every year so a five-star score from 2019 doesn’t necessarily equate to a five-star result in 2024.
Eco Rating
As of January 2024, our eco rating is based purely on official carbon dioxide (CO2) tailpipe emissions data for each model, averaged across all the different versions available (petrol, diesel, hybrid, plug-in hybrid) for each car.
Electric cars produce zero tailpipe CO2 emissions, so they automatically score 100% in this category.
Plug-in hybrids officially produce very low CO2 emissions, but in the real world this very much depends on how often the car is charged from an external charging point and how much driving is done with the electric motor rather than the petrol (or diesel) engine. All we can do is use the official government data.
We realise that this doesn’t usually reflect the overall pollution produced by electric cars, as the electricity has to come from somewhere – potentially a coal- or gas-fired power station. However, we firmly believe that tailpipe emissions are a critical contributor to human health, especially in towns and suburbs where most people come into contact with cars, so tailpipe emissions are still an important and relevant factor. To be fair, CO2 emissions also don’t account for how efficiently oil is extracted, transported and refined into petrol or diesel, before finding its way to your local service station, so it roughly balances out.
There are plenty of nasties other than CO2 in car exhaust, but they are broadly produced in line with CO2emissions, so this data point is a reasonable representation of overall tailpipe emissions.
We also show Green NCAP eco ratings for each car where they are available, including air quality and energy efficiency ratings for each model and engine tested. However, relatively few cars are tested by Green NCAP each year, which is insufficient for us to use in calculating our Eco Rating.
We are currently assessing additional data sources to strengthen our Eco Ratings, so stay tuned.
Reliability Rating
We include reliability data from one of our commercial partners, MotorEasy. This is taken directly from MotorEasy’s network of service centres, both from franchised dealers and independent garages. We also look at warranty claims for each model, assessing both the number of claims and the average cost of the claims.
MotorEasy also provides reliability data to many other sources, such as the What Car? Reliability Award.
Running Costs Rating
We take running cost data from our technical partner, Clear Vehicle Data. Analysing millions of data points, we provide average scores across a model range for the biggest expenses when running a car. These are:
- fuel consumption
- CO2 emissions (which affects road tax and other charges)
- insurance group (a crucial factor in your annual car insurance premium)
- servicing, maintenenace and repair costs (covering the first five years)
Clear Vehicle Data also provides running cost data to many of the UK’s top leasing and fleet companies.
We have separate algorithms for new and used car running costs, which use different weightings and servicing data points.
Security Rating
Some cars display a security rating, which is based on a theft prevention assessment by Thatcham Research. This includes theft by relay attack for keyless entry/keyless start systems.
The programme started in 2019 but was discontinued in 2021, so very few cars display this security information. AS such, it’s not included in our Expert Ratign calculations. We still display this information for cars that have been tested, as it’s useful for potential customers, but no new additions to the Index will have a security rating.
Thatcham Research is also the UK’s member of Euro NCAP. Along with sister organisations in other European countries, it conducts many crash tests and other assessments for Euro NCAP ratings each year.
FAQs
How can you justify your ‘gold standard’ claim?
Rather than one person’s opinion or one website’s view on what makes a car good or bad, we compile and analyse new car reviews from 35 of the top UK motoring websites. Then we apply a complex set of calculations to bring you the definitive rating for every new car.
Our advanced Expert Rating algorithm factors in the age of the review and the scoring methods used by all 35 different sites. Every day, it recalculates and updates the Expert Rating score for every single car. The scores for every car can shift every time a new review for any car is added to the database.
For car buyers, it’s an easy-to-use guide to all the key information on each new car. You can see, at a glance, what each website has said about a car, and click on a link to visit that site and read the full review. We also include complete Euro NCAP safety ratings, Green NCAP eco ratings and a list of any awards the car has won.
So far, we have published more than 500 new car ratings and we’re adding more each week. Our database contains more than 15,000 individual reviews and is growing daily. We currently track 35 automotive titles and we’re currently reviewing the sites we include – with a view to either removing some existing sites and/or adding new sites. We’re also testing how the results are changed by reducing that number to 30 sites or expanding it to 40.
How do you calculate the Expert Ratings?
The Expert Rating score is an aggregated rating made up of a number of individual review scores. Unless it’s a very niche model, we usually require a minimum of 12 scored reviews before we include a car in our Expert Rating Index. Some cars have more than 60 reviews used in our calculations.
When we launched the Expert Rating Index in 2019, we used a simple average of all the review scores to determine the Expert Rating score. While this was much better than relying on any one single score, it had limitations based on aggregating reviews from different sites with very different scoring systems and methodologies. So we developed version 2.0, which rolled out in 2021.
Version 2.0 of the Expert Rating Index used a “weighted average” of all the reviews of a that model published by the 30 sites we include in the Index. We factored in the age of each review (newer reviews carry more weight than older reviews) and we normalised the scores from each publication to account for variations in how they each score their reviews. Over time, we also increased the number of media sources to 35 titles and added a separate rating for used cars.
The latest generation of the Expert Rating Index is Version 3.0, which rolled out in January 2024. This is an exponential jump in terms of the amount of data we pull in to create each car’s Expert Rating, and we have added individual categories for safety, environmental impact, reliability and running costs. The previous Version 2.0 score is now the Media Rating. We have also more clearly separated ratings for new and used cars, using different criteria and weightings to reflect different customer priorities.
We are continuing to develop the latest version of the Expert Rating Index, and Version 3.1 will add at least one more category and some additional data sources. Stay tuned…
So how exactly are the scores calculated?
Scores for each category (media, safety, eco, reliability and running costs) are calculated using complex mathematical algorithms. We use both an A-F report card format as well as percentages to provide both simple and detailed scores for each category.
The data from each category score are then funnelled into two more algorithms to create overall New Car Expert Rating and Used Car Expert Rating scores.
If you want to know how our algorithms work, then bad luck. That information is classified Ultra Top Secret and is above your security clearance.
That car’s score has changed twice in the last month. Why is that?
It’s perfectly normal for Expert Rating scores to shift up or down over time – the percentage scores will change more frequently than the headline A-F scores – and there are a few reasons for that happening.
Firstly, we are constantly adding new data to our database. New car reviews are published daily, safety ratings are published monthly, and our reliability and running cost data are updated almost constantly.
Secondly, some media sources will adjust their reviews scores over time. This may be as cars are re-evaluated against newer rivals, or it may be for a specific reason if particular issues have been uncovered. Similarly, Euro NCAP will sometimes re-test cars after several years if they are still on sale, which often results in their safety ratings bring downgraded.
Thirdly, new car reviews and safety scores are weighted for age. Older tests carry less weight than newer tests, which means the overall score is more influenced by newer data. Usually (but not always), a car’s scores will gradually decrease over the course of its production cycle as it slowly goes from being the hottest new model on the block to being old and outdated at the end of its life.
Finally, our advanced algorithm automatically accounts for any changes in scoring scales or methodology from any of our sources.
Which publications contribute towards the Expert Ratings?
The original Expert Rating Index was launched in 2019 and tracked 12 sites, concentrating on the largest and best-known automotive publications that review the most cars. Over the last five years, we have broadened that out to a current total of 35 carefully selected sites, including national newspaper sites that have substantial and regular motoring content. We have also added specialist titles that target specific areas of the new car market (green cars, fleet buyers, performance cars, etc).
As of January 2024, the list is:
Auto Express, Auto Trader, Autocar, Business Car, Car, Car Keys, Carbuyer, Carwow, Company Car Today, Daily Mail, Daily Mirror, Discover EV, Driving Electric, Electrifying, Eurekar, Evo, Fleetworld, Green Car Guide, Heycar, Honest John, Motoring Research, Motors.co.uk, Move Electric, Parkers, Regit, The Car Expert, The Intercooler, The Scotsman, The Sun, The Sunday Times, The Telegraph, Top Gear, What Car?, Which?, and Which EV?
Why have you selected those sites?
We have a range of criteria for inclusion, but mainly we’re looking at the quality and quantity of reviews. We also consider the variety of cars reviewed by each publication and how the reviews are scored. We only take websites into account, rather than printed titles, with links back to the original review sources so you can read them in full for yourself.
We review our media sources periodically and sometimes remove some sites from the Index if we don’t think they are contributing sufficiently to warrant their ongoing inclusion. Our next review is set for late 2024, when we will decide whether to add any new sites and/or remove any existing ones from our calculations.
We only use UK sites in our Expert Rating Index, although many of the reviews are conducted in Europe or other parts of the world as part of a new model’s global press launch. A car’s pricing and specification can vary dramatically around the world, so a review from a US or European website won’t necessarily reflect that car’s position in the UK market.
Does anyone else use your rating technology?
Our aggregated ratings are available to licence. The data is already being used by Leasing.com, one of the UK’s leading leasing comparison sites. Leasing.com’s ratings are powered by the same media review data as our own Expert Rating Index, but we run them through a bespoke algorithm to provide a unique set of scores.
If you would like to enquire about licensing our ratings, please email editor@thecarexpert.co.uk.
How often are the Expert Ratings updated?
We’re updating information in the Expert Rating Index daily, although that doesn’t mean we update every car every day. On average, each car will be updated about once a month so the information is about as current as you’ll see anywhere.
How do you decide which cars to add to the Index?
We have almost every new car on sale and we’re working as fast as we can to get the rest. Currently, there are only a few niche models not currently listed.
Broadly speaking, we prioritise the UK’s most popular cars, as well as those with the most data available. Inevitably, that means there are more small cars and SUVs than supercars.
We’re also adding more used cars to the Expert Rating Index, since 90% of all households buy used cars rather than new. Getting quality data from older models is tricky, as there are fewer sources available. This is another reason why we have separate Used Car Expert Ratings for each car.
How do you separate different versions of the same car?
It can get tricky deciding whether to lump different versions of a model together or rate them separately. We look at this on a case-by-case basis.
For example, the Audi A4 has a multitude of different variants. We include the saloon, Avant (estate), A4 allroad and S4 versions all under the one general umbrella of “Audi A4”. But the Audi RS 4 is considered separately because it’s a very different vehicle.
Similarly, we always consider electric models separately from equivalent petrol/diesel/hybrid models. A good example is the Vauxhall Corsa (petrol) and the Vauxhall Corsa Electric.
Do you include owners’ reviews from any of the sites?
No, we don’t currently count user reviews, even though some of the sites we track display owners’ ratings or carry out owner surveys (like the annual Auto Express Driver Power survey).
Owner reviews have some good points, but they can also be problematic. Most of the time, owner surveys are completed by people who’ve just bought a new car and are still in love with it, or by those who have had a bit of a nightmare and want to vent about it. This tends to create a very polarised data set of very good and very bad reviews, rather than balanced and objective opinions that encompass a range of scores. You see the same thing across the internet in almost all situations – just look at customer reviews on Amazon, for example.
Owner reviews are also much harder to verify and easier for PR and marketing departments (or salespeople, Russian bots, MI6…) to influence, whereas reviews from recognised media sources and journalists are more reliable and trustworthy.
We are investigating ways of aggregating different user reviews to create an Owners Rating category, but so far we have found the data to be too sporadic and unreliable to provide a valuable score that readers can trust. We’re still working on it, so watch this space.
Can you add my site to the Expert Rating Index?
We are currently reviewing the websites we include in our Media Rating category, with a view to adding and/or removing sites. We have a range of criteria for inclusion, but mainly we’re looking at the quality and quantity of reviews, the variety of cars reviewed and how the reviews are scored.
We only take websites into account, rather than printed titles, so we can always link back to the original review source.
We’re always open to additional data sources, and are working hard to continue growing and developing the Index with the best possible data available. If your company provides industry data that could be of use to UK car buyers, we’d be happy to chat to you about it.
If you would like your site to be considered for inclusion in our Index, please email editor@thecarexpert.co.uk.
Last updated: 27 April 2024
