Dear John: I never noticed this before because I always used 87 octane gasoline.

My new car requires 89 octane. The price difference between 87 and 89 ranges between 20 and 60 cents, depending on the station. Any insight into this? M.R.

Dear M.R.: I asked the US Energy Information Agency, because those people know it all — in the good sense of the phrase. And the answer isn’t that surprising.

“It’s a combination of higher manufacturing (refining and blending) costs; supply and demand for the octane-enhancing components of gasoline, and retail pricing to what the market will bear,” says my source at the EIA.

If you want to know more about why you are being screwed, here is the EIA’s long explanation: “Growing octane needs widen the price difference between premium and regular gasoline.”

Personally, my inclination is to just go with the 87 octane. But that would probably void your warranty, so I guess you shouldn’t do that.

Happy motoring!