He runs so much faster than me. The FORMAL way is: He runs so much faster than I. ...however a great deal of people do say "He runs so much faster than me." ... Choose the form that best matches tone and formality level of your writing !!

Going to the answer below to add a bit more. That might be formally used, but in all seriousness, on a day to day level most native speakers tend to say 'me'. You might also say "faster than I do"