| Share | Phrase |
|---|
| 23.67% | inefficient [effectiveness] operation |
| 17.98% | inefficient [effectiveness] burning |
| 15.91% | inefficient [effectiveness] combustion |
| 9.10% | inefficient [effectiveness] engine |
| 8.61% | inefficient [effectiveness] screw |
| 7.81% | inefficient [effectiveness] system |
| 6.07% | inefficient [effectiveness] use |
| 5.91% | relatively inefficient |
| 4.92% | very inefficient |