Originally Posted by roadfix
This is assuming your grill is operating at or near peak performance.
Gas grills don't operate efficiently if the burners are not clean and full of gunk, resulting in much lower temps. Also, if using lava rocks, make sure they're spaced evenly, not full of gunk, and not restricting heat flow.
Thanks for the info. It's a fairly old grill and, based on your description, I'm pretty sure it's not performing at peak efficiency
I did grill a porterhouse on it yesterday, which came out beautifully seared and cooked medium-rare, just like we like it
I really think the meat thermometer is the key.