DriveSmart allows users to search and compare UK cars using structured vehicle data, including emissions-related information where available.
Vehicle emissions are important for company car drivers, fleet operators, salary sacrifice schemes and private motorists who want to understand the environmental and tax position of different vehicles.
This page explains the main emissions factors used when comparing cars, including CO2 emissions, WLTP figures, Real Driving Emissions testing, Euro emissions standards, NOx, particulates and electric vehicle emissions.
DriveSmart provides factual comparison data. It does not recommend cars or rank cars as best or worst.
Search For Cars By Emissions
Why Search For Cars By Emissions?
Emissions are one of the key factors used when comparing cars, particularly where the vehicle will be used as a company car or as part of a business fleet.
CO2 emissions can affect company car Benefit-in-Kind tax, Vehicle Excise Duty and environmental reporting. Other emissions, such as nitrogen oxides and particulates, may also be relevant for urban driving, clean air zones and fleet policy.
A car emissions search can help users narrow the vehicle dataset using environmental and technical criteria rather than relying only on manufacturer, model, body style or price.
Understanding CO2 Emissions
Carbon dioxide emissions are normally shown in grams per kilometre, often written as g/km.
CO2 is especially important in the UK because it is used in several vehicle tax calculations. For company cars, the official CO2 figure is one of the main factors used to calculate the Benefit-in-Kind percentage.
Lower CO2 cars usually attract lower company car tax percentages. Fully electric cars normally have the lowest company car tax percentages because they have zero tailpipe CO2 emissions.
WLTP Emissions Figures
WLTP means Worldwide Harmonised Light Vehicle Test Procedure.
WLTP is used to produce official figures for fuel consumption, CO2 emissions, electric range and energy consumption. Together with Real Driving Emissions (RDE) testing, it forms part of the modern vehicle emissions approval process.
These figures are measured under controlled test conditions so that vehicles can be compared on a consistent basis.
Real-world results may differ from WLTP figures because actual emissions and energy use depend on driving style, speed, traffic, temperature, load, journey type and charging behaviour for plug-in vehicles.
Real Driving Emissions (RDE)
While WLTP provides a standardised laboratory test, Real Driving Emissions testing was introduced to help ensure that vehicles also perform well in everyday driving conditions.
RDE testing is carried out on public roads using Portable Emissions Measurement Systems, often referred to as PEMS. These systems measure emissions while the vehicle is driven over a range of routes, speeds, traffic conditions and temperatures.
The introduction of RDE testing was particularly significant for diesel vehicles because it helped address concerns that some vehicles produced higher emissions in real-world driving than during laboratory testing.
Modern Euro 6d and Euro 6e standards combine laboratory testing with real-world emissions requirements, providing a more comprehensive assessment of vehicle emissions performance.
Although no test can perfectly reflect every driving situation, WLTP and RDE together provide a more realistic picture of vehicle emissions than earlier testing procedures.
Petrol Car Emissions
Petrol cars produce tailpipe CO2 emissions when fuel is burned. They may also produce other regulated emissions, including carbon monoxide, hydrocarbons and particulates.
Petrol cars often have lower NOx emissions than comparable diesel cars, although the exact position depends on the vehicle, engine, emissions system and test standard.
Petrol vehicles may be relevant where users want to compare purchase price, fuel type, emissions, running costs and company car tax together.
Diesel Car Emissions
Diesel cars often produce lower CO2 emissions than comparable petrol cars because diesel engines can be more fuel efficient.
However, diesel vehicles have historically been associated with higher NOx emissions, which is one reason why Euro emissions standards and modern exhaust treatment systems are important.
Diesel cars may still be relevant for high-mileage users, but emissions, tax, clean air zone exposure and running costs should be considered together.
Hybrid And Plug-In Hybrid Emissions
Hybrid and plug-in hybrid vehicles combine an internal combustion engine with electric assistance.
A conventional hybrid does not usually need to be plugged in. A plug-in hybrid electric vehicle can be charged externally and may be able to complete shorter journeys using electric power.
Plug-in hybrid emissions can vary significantly in real use. The official CO2 figure assumes a particular test cycle, but real-world emissions depend heavily on how often the vehicle is charged and how much of each journey is completed using electric power.
Electric Car Emissions
Battery electric cars produce no tailpipe emissions. They have no exhaust CO2 emissions, no exhaust NOx emissions and no exhaust particulate emissions.
For regulatory purposes, battery electric vehicles are classified as zero-emission vehicles because they produce no tailpipe emissions while being driven.
This makes electric cars particularly relevant for company car tax, salary sacrifice schemes, urban driving and fleet emissions reporting.
However, electric vehicles still use electricity. The wider carbon impact depends partly on how that electricity is generated.
Electricity Generation And Power Station Emissions
Electric cars do not produce tailpipe emissions, but electricity generation may produce emissions depending on the source of the electricity.
Electricity may be generated from renewable sources, nuclear power, gas-fired power stations or other sources. The carbon intensity of electricity can therefore vary over time.
DriveSmart already includes an electric car carbon footprint calculator that considers battery capacity, battery range, annual mileage, renewable electricity percentage and power station CO2.
Users who want to estimate the wider carbon footprint of an electric car can use that calculator rather than relying only on tailpipe emissions.
NOx And Particulate Emissions
Vehicle emissions are not limited to CO2.
Nitrogen oxides, often referred to as NOx, are regulated pollutants that can be relevant for air quality. Particulate matter is also regulated because very small particles can affect local air quality.
NOx and particulate emissions are particularly relevant when comparing petrol, diesel, hybrid and electric vehicles for urban driving or fleet policy.
Euro Emissions Standards
Euro emissions standards set legal limits for regulated pollutants from vehicles.
Examples include Euro 4, Euro 5 and Euro 6 standards, including Euro 6e-bis requirements for certain plug-in hybrid vehicles and the forthcoming Euro 7 standard. Later standards generally impose tighter limits on pollutants such as NOx, carbon monoxide, hydrocarbons and particulates.
Euro 7 is expected to apply to new car and van vehicle types from 29 November 2026. It is intended to continue the development of emissions regulation, including areas such as exhaust emissions, brake particles, tyre particles and battery durability.
Euro emissions standards can be relevant for clean air zones, low emission zones and business fleet policies, especially where vehicles operate in towns and cities.
Company Car Tax And Emissions
For company car users, CO2 emissions are a central part of the Benefit-in-Kind calculation.
A lower CO2 figure normally means a lower Benefit-in-Kind percentage. Fully electric cars usually sit in the lowest company car tax bands because they have zero tailpipe CO2 emissions.
This is one reason why emissions search, fuel search, company car tax calculations and running cost comparisons should be considered together.
Using Car Emissions Search With Other Search Tools
Emissions are only one part of a vehicle search.
Users may also want to compare emissions with body style, fuel type, gearbox, seats, manufacturer, model range, budget, equipment and running costs.
DriveSmart search pages are designed to work together so users can start with a broad search and then move to more specific filters where required.
Search Cars By Emissions
The DriveSmart car emissions search page is intended to help users compare cars using emissions-related data where available.
This can include CO2 emissions, fuel type, electric vehicle information and other emissions-related fields depending on the structure of the vehicle data.
The search tool should be used as a factual comparison tool rather than as a recommendation engine.
Search For Cars By Emissions
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