octane, octan

Octane or octane means a chemical, made from petroleum, and used to make a type of gasoline that makes a car run more smoothly, without engine knocking, or without running noisily and irregularly --
The car may run better if you use a high-octane gasoline.
Check the octane rating at the gas pump.

Octan or octan describes a fever that returns every eight days --
He has an octan fever, and today he's feeling ill.
If she has an octan fever, she'll be sick again in eight days.

Now that you know that, you can say --
"The car seems to knock only sometimes, as if it had a mechanical version of an octan fever; a gasoline with a high octane level may help."

Note--"high-octane" is also a slang term meaning supercharged or powerful --
The star gave a high-octane performance, and the fans went wild.