Consumers must also be given information on the suppliers overall fuel mix at the point of sale.

"You can't eliminate 80 percent of your fuel mix," she said.

The fuel mix and associated carbon intensity of most sectors have tended to be very stable over time.

Weapons grade plutonium can be added to the fuel mix.

The system responded by continuing to diversify its fuel mix.

"Ross, do you really think this fuel mix is what we're looking for?"

Such engines, however, would only be cleaner if they used a carefully blended fuel mix injected at the last moment.

The engines, which must be lightweight, use a very rich fuel mix.

"The idea was to create a more diverse fuel mix," he said.

This is probably to keep the fuel mix concentrated around the spark plug for better combustion.