What is the fine-grained topic of the following text: CO2 emissions which have been reduced to 189g/km, down from 199g/km on the previous 4x2 manual transmission model, while fuel economy is now up to 39.2 mpg, compared with 37.2mpg over the model it replaces. Only return the topic.
Reduced CO2 emissions and improved fuel economy in a new car model.