All this talk of "driving it like you stole it" is BS IMO.
I have 4000 miles tracked with Fuelly and I am barely over 30 MPG. Figure it out.
I drive the vast majority of those miles on the highway.
In other words...within the limits of sanity...and with the help of $2500 in CHP Defense...I am putting as much "load" as can be reasonably expected.
If I experience carbon build up, then ANYONE can.
Only time will tell.
It is unreasonable to expect that the average consumer would drive like I do.