My grannying period was both times I broke in the engine. I once got 17.4 MPG.
The only time I came up on a GTR while on a twisty mountain course and I was limited to 4,000 rpm's (break in). It was plenty. The idiot who bought this GTR, CA liscense plate OHMU, was useless.
Not that it has stuck with me this past year plus.