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

Brian Whatcott wrote:

Oh yes, they tend to run them on natural gas. That's quite a favorable
factor, apparently.

I have to ask: why?

It's a very clean-burning fuel and the oil lasts for ages, or more
accurately, keeps hold of its properties a fair bit longer than oil
that's steadily getting mankier and mankier in a petrol engine.