Earlier this week it was reported that the wrong fuel was delivered to just three gas stations. However, that number has now expanded to six locations.
The Consumer Affairs Division says the fuel, which is used in propeller-driven aircraft and not jets, was sold as super unleaded fuel between Wednesday and Friday of last week.
Officials say automotive experts say the gas should not damage car engines.
Consumer Affairs officials have received about 30 complaints from motorists who purchased the higher octane fuel.
The stations are owned by Freehold-based Pasmel Property. The stations are Delta, 88 Route 36 South, Keyport; Getty, 1292 Route 22 East, North Plainfield; Express Fuel, 2482 South Broad Street, Trenton; Lukoil, 218 Parker Avenue, Manasquan; Lukoil, 2239 North Avenue, Scotch Plains; and Pasmel, 2515 Brunswick Pike, Lawrenceville.