Well, I usually don't hit 60 at all, since only one short stretch of my commute is even 55 mph limit. That's part of my secret: a good route.
I haven't measured, but it's probably about 15 sec to 40 mph. I'm still in the ballpark of other traffic while accelerating. 1st gear only to get rolling (5-10 ft), 2nd up to 10 mph, 3rd up to 20 mph, then 4th gear up to 40. I usually stop there and glide down to 20, then pulse back to 40. If I'm in a hurry I'll use 5th gear with 30-50 mph pulse-and-glide instead, and lose about 5% mpg.
Gauges to use (I have Scanguage which shows 4):
- Trip mpg - my most important gauge. Keep this moving up for the entire trip. If you must lose some on a hill, gain it back and more on the other side.
- Load - 85-90% load for acceleration is most efficient.
- water temp - for diagnostics
- volts - for diagnostics, especially with engine-off coasting and headlights
- instant mpg - if I had another spot, I'd show this one