I honestly don't drive it fast by any means. I'm never flying past traffic, although sometimes keeping up can be 70-80 mph but most of the time the speedo is under 70mph and I know it's 4mph fast at highway speed. I'll have fuel mileage to post in a month, comparing all mileage since new vs using fuel power. I have that posted with the camaro somewhere around here. There's been articles claiming a lot of foreign automaker's mileage claims have been exageratted, it was also in relation to that SAE article I read about the LS7 which is why I remember it, describing the new test being used to rate engine power under a more controlled and less variable test because manufacturers were tweaking environment conditions and whatever else they could to produce the greatest hp/tq numbers and i'm sure also the highest fuel economy numbers.
sure you can interpret the numbers as hp per liter so a Honda S2000 or Acura nsx has more, but their total output is only 237 and 290 hp. Putting out 500hp, even 400+, consistently and i'll dare to use the word 'reliably' from a factory production non-assisted engine, running on pump gas, is something different!
I'm not saying pushrods are better, but the reason they are still around are because they are that good, they are reliable, and some will say cost less to produce than an OHC/DOHC engine.