| Answer | Crossword Clue |
|---|---|
| REV | Run the engine |
| REV | Run up the engine |
| IDLE | Barely run the engine |
| IDLES | Lets the engine run |
| REV | Run up an engine |
| TESTBED | Engine trial-run support |
| WHIR | Run like an engine |
| SPUTTER | Run roughly, as an engine |
| PURR | Run smoothly, as an engine |
| PURR | Run well, as an engine |
| HUM | Run smoothly, as an engine |
| IDLE | Barely run, as an engine |
| TUNEDUP | Made run better, as an engine |
| SMOOTHLY | How a well-oiled engine should run |
| PURR | Run like a charm, as an engine |
