Hi: I am giving my car to a family member who never buys premium fuel, and I am not sure if they ever will. I cannot find my OEM chip so will filling with 89 do damage to my engine? It is my mother and she will not be redlining the car ever...70th birthday present. Thanks

nf
'00 540/6
'99 323i
'90 535i
'73 2002
'70 2800CS