not really, ur only adding a lil bit.. done it many times before on carb engines.. u are only adding a gal or so mayb less then your fillng it up after u test.. but also like i said fix it first.. then as a last resort do the meth trick.. i know in some states you dont pass the smog u cant drive it then no ride to work.. so if all else fails use the meth... actully 1/2 gall will clean it up pretty good.. did this on my 74 van many yrs ago.. had carb issues.. no money and no job. had to do what i had to do..van is still runing same fuel system, no problems.. i did fix the carb tho, same fuel lines.. my local NAPA gave me this trick and the meth