Should we be changing oil by hours on oil instead of miles on oil? I started thinking hour meters should be on vehicles also. Let say you average 50 MPH for 200 hours on oil it works out to 10,000 miles. Let say you average 25 MPH for 200 hours on oil it works out to 5000 miles. Seems reasonable But now let say you only drive a vehicle around town and only average 14 MPH suddenly were down to 2800 mile OCI for 200 hours. Now let say you do 7500 miles OCI with a 15 MPH average in stop and go city traffic were up to 500 hours on the OCI. Is changing oil by miles driven a crude way to do it?