If you have proof that the fuel is not compliant you report to Ministry of Energy, Science, Technology, Environment and Climate Change (MESTECC) or the Department of Environment.
Thru the powers under the Environmental Quality Act 1974 they imposed standards on Euro4 and Euro5 for petrol and diesel, more specifically the Environmental Quality (Control of petrol and diesel properties) regulation.
Anyone found to have made an offence under this Act can be fined or jailed.
EURO6 is not a fuel standard.
It is a emission standards for cars, vans, lorries, buses and etc.
Your car has to be certified that it is EURO6 compliant.
There are a few types of Diesel available, either EURO2M (Black hose) or EURO5M (Blue hose). The price difference between the 2 is 10 sen.
EURO4M is more environmentally friendly compared to EURO2M due to the significantly less sulphur content. Other countries such as Singapore are already using EURO6 fuel.