Tool: how far can I travel in x hours?

Really? If I drive 55 mph for 10 hours, I go 550 miles. If I drive 65 mph for 10 hours, I go 650 miles. If I drive 75 mph for 10 hours, I go 750 miles. So by driving 20 mph faster, I can go 200 miles further. I think I have saved far more than 15 or 30 minutes.

It takes 13.6 hours to go 750 miles at 55 mph. Looks like a savings of 3.6 hours going 20 mph faster. It takes 11.5 hours to travel 750 miles at 65 mph. That's a savings of 90 minutes. Quite a bit more than your 15 or 30 minutes.

There are a few problems with your premise; Unless you have the road to yourself, you can't average 75 miles per hour. Lord knows I've tried. In a typical car, with my lead foot, the best I've managed is to average 65 mph for 12 hours. That means there are many times you have to be in excess of 75 mph to keep an average of 65.

That being said, if you keep the throttle at 65 you will not average 65 in the long run. It will be slower as there will be traffic, hills, and construction, even if you had a giant fuel tank, no need to sleep and inserted a catheter.

Most folks here claimed 400 miles per day or less, but let's do the math at 500 miles per day;

500 miles at 65 mph = 7 hours 41 minutes
500 miles at 60 mph = 8 hours 20 minutes
500 miles at 55 mph = 9 hours 6 minutes

We know from practical experience to truly average 65 miles per hour you'd have to spend much time over 75 mph. If you drive like I do, and cap out at 65 with the occasional 70 to pass someone, you're going to average more in the 60 mph range.

Each 5 mph added will save 40 minutes over the day's driving. Not dilly-dallying around at the pit stops can also save that 40 minutes without the expense of the fuel, tickets, added wear and tear on the RV, and the white knuckles.

I'd love to haul my TT down the road at 80 mph, but I know better thanks to the fine folks on this forum.