Fast food giant McDonald's is trying to be more environmentally friendly by re-using its cooking oil to power its delivery trucks in the UK.
Scientists have found a way of recycling the oil that burgers and chips are cooked in as a fuel that makes a lot less pollution than petrol.
The fast food chain has been criticised in the past for not being green enough.
Now, after a successful trial, bosses say they are expecting to convert about six million litres of oil every year.
They have also promised to convert all 155 of their trucks to be able to run on the green fuel - called bio-diesel - by next year.