grease the wheels
Also, oil the wheels. Make things run smoothly, as in You can count on Ben to grease the wheels so we'll be waited on promptly. This metaphoric expression transfers literal lubrication to figurative. [Mid-1600s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.