Originally Posted by mick

don't know but your 370z should run fine at 45 mph in 6th gear.
my 2.5 liter beetle is a lot weaker and even it runs fine at 40 mph in 5th gear.

i think the recommendation of driving in 5th gear at 45 mph is for 4-cylinder cars with 1.5 liter engine, not for 6-cylinder cars with 3.7 liter or larger engine.