5W30 vs 5W40 engine oil for high-mileage cars in the UK - which is better?

For vehicles with over 100,000km mileage in the UK, 5W40 engine oil is generally recommended as it provides better sealing and engine protection. The higher viscosity of 5W40 oil improves engine compression and power output in older vehicles like the popular UK models Volkswagen Golf or Ford Focus with high mileage.

Key differences between 5W30 and 5W40 oils:

1. 5W30 offers better fuel efficiency and faster engine cooling due to its lower viscosity, making it suitable for newer vehicles such as the BMW 3 Series or Mercedes C-Class.
2. 5W40 provides superior protection for worn engines with its thicker consistency, reducing noise and maintaining stable oil pressure - particularly beneficial for older models like the Vauxhall Astra or Nissan Qashqai.

When choosing between these oils for your UK vehicle, consider factors like manufacturer recommendations (check your car's handbook), typical driving conditions (motorway vs city driving), and the vehicle's service history. For most high-mileage petrol and diesel cars on UK roads, 5W40 offers the optimal balance of protection and performance.