Some South Dakota gas stations are selling lower-octane fuel without telling customers about it.
Selling 85-octane gasoline became legal in South Dakota earlier this month. But the law change says gas stations have to post a warning to customers if they're doing it. Lower-octane fuel can cause knocking and damage car and truck engines.
Several Rapid City stations haven't been displaying a required notice to warn customers about the fuel. They're supposed to be reminded to check the owners' manuals of their vehicles before using 85-octane gasoline.
State rules don't have any penalty for fuel retailers who don't post a warning label. A spokesman for South Dakota's Department of Public Safety says inspectors tell gas station operators about the requirement.