We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Jethro
saying something like:

When I worked in the motor trade, I would despair of people - egged on
by the AA - who thought a spray of WD40 was actually a full service.
In reality, the *proper* job was to keep the HT leads clean, to
prevent moisture settling. Once WD40 had been used, you'd get a layer
of grime, which actively trapped moisture, and made it impossible to
start the car.

And often you'd get deterioration of the leads themselves, through the
WD40 acting as a solvent on the covering. Turned some of them into a
sticky mess, it did.