UK motorists are being urged to follow the 45mph rule when driving this week as the country experiences its third heatwave of the year, with temperatures expected to reach 34-35C in some areas. The advice comes from motoring experts who say that using air conditioning or opening windows at the right speed can significantly affect fuel consumption.
Heatwave Conditions and Forecast
According to the Met Office, a prolonged spell of hot and dry weather is set to bring temperatures into the low 30s Celsius across much of southern England from the start of the week, with some locations potentially reaching 34-35C later in the week. Conditions are expected to be less humid than during June's heatwave, with lower peak temperatures and fewer exceptionally warm nights.
Met Office Deputy Chief Forecaster Steven Keates said: "Parts of the UK are entering heatwave conditions: the third heatwave in the UK so far this year. However, unlike the May and June heatwaves, we are not expecting this heatwave to be record-breaking."
The 45mph Air-Con Rule
Mike Fazal, motoring expert and CEO of Leasing.com, advises drivers to follow the '45mph air-con rule' to save fuel. He explains that below 45mph, it is usually more fuel efficient to open windows and let air flow through the cabin. Once travelling faster than around 45mph, especially on dual carriageways or motorways, open windows create aerodynamic drag that makes the engine work harder. At that point, using the air conditioning can become the more fuel-efficient choice.
Research suggests air conditioning can increase fuel consumption by around 10%, while driving with windows open at higher speeds can increase fuel use by up to 20%. By following the 45mph rule, drivers can optimize their fuel efficiency during hot weather.
Safety Measures for Drivers
In addition to fuel-saving tips, drivers are reminded to take safety measures to avoid heat-related illnesses. This includes applying suncream, staying hydrated, and staying in shaded areas when possible. Another important aspect is footwear choice. Hot weather often leads drivers to swap their usual shoes for flip-flops, clogs, or Crocs, but not all summer footwear is suited to driving.
Fazal warns: "Drivers need to be in full control of their vehicle at all times. If your footwear slips, becomes caught or makes it harder to operate the pedals safely, it could contribute to a careless driving offence. While flip-flops and Crocs might be comfortable in hot weather, they're not the best choice behind the wheel. Over summer try keeping a pair of trainers in the car and changing into them before setting off."
Careless driving offences can result in three to six penalty points and fines of up to £5,000, while more serious cases may carry five to nine penalty points, driving disqualification, and in the most severe circumstances, unlimited fines.
