Even such an efficient engine, if large enough to deliver the proper performance, would have a low average fuel economy.

I have really developed a very efficient solar engine.

This provided a very efficient engine, which won many awards both at home and abroad.

The higher octane would permit the design of a more efficient engine.

Coal was used to power ever more efficient engines and later to generate electricity.

And yet he worried about it: "Do you think the oil companies are going to let me develop a more efficient engine?"

This allows a smaller, more efficient engine to be used.

It is therefore necessary to produce efficient and economical engines.

They have a quite efficient engine of destruction - a "rifle" is their thought.

But by the end of the decade, smaller, more efficient engines had been developed and were starting to come on the market.