you can absolutely run regular fuel in these things...no doubt about it..the computer is actually set for that possibility. That's why when you may 'chip' the computer you must absolutely use premium, it insists upon premium fuel whereas the stock chip expects you to probably/possibly not. It's programmed for potential thriftiness ...... actually throwing premium in an around town car is worthless....As to potentional engine damage..none...remember, the fuel concerns contribute to car manufactures in a political type of fashion....