2nd gear @ 3000 rpm (about 45mph in my car) as long as you can stand it.

Some folks would go higher rpm in higher gears, but then the police get involved.

Historically, the point is to run the engine fast enough, long enough, to help it break up and blow out carbon deposits that might be in the combustion chambers.

Sometimes helps to add some of the cleaner that goes into the gas tank, like Techron (from Chevron).

If you can, it it probably better to do normal highway speeds for a long time, like several hours, than it is to 'blow the cobs out' for a few blocks in town.

Sometimes, improvement from this sort of thing is mostly in one's imagination.

Probably won't hurt anything as long as rpm's (and speeds) are kept reasonable, might be fun.

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