10 ppm diesel contains a maximum of 10 parts per million (ppm) of sulfur, significantly reducing sulfur dioxide (SO₂) emissions. This low sulfur content helps improve air quality and mitigate the effects of acid rain, making it an environmentally friendly choice. It complies with the strictest EU emissions standards, making it suitable for use in most modern diesel engines. Additionally, this fuel is generally compatible with advanced emission control systems, such as diesel particulate filters (DPF) and selective catalytic reduction (SCR) systems, ensuring optimal performance and reduced emissions. 

500 ppm diesel contains a maximum of 500 ppm of sulfur, leading to significantly higher SO₂ emissions compared to its lower sulfur counterparts. The increased sulfur content can contribute to environmental issues such as acid rain and poor air quality. This higher sulfur variant is becoming less common in the EU due to stringent regulations, though it may still be found in some markets or used for specific applications. While it can work in older diesel engines, this fuel is not compatible with modern emission control technologies and may result in increased engine wear and fouling over time.