Originally Posted by dognamedboo
...WD was the 40th attempt at making a Water Displacement formula. It's really thin as an oil and disappears pretty quick...
As a kid, I sprayed WD-40 on fishing reels, then noticed a gummy residue as the carrier evaporated.
That residue interfered with the reel operation, and was an all-around bad idea.
The 'water displacement' formula was developed decades ago.
In the decades since, we developed specific lubricants to fit individual requirements for shear resistance, heat-tolerance, and corrosion prevention.
If moisture in your distributor cap is preventing your spark-plugs from firing (or firing in the correct order), a 'water displacement' spray might get you moving again.
Or wipe around the contacts with a paper-towel.
Or just wave a warm hair-dryer at it.
On computer-controlled or diesel engines, WD-40 is an anachronism.