Spearfish SD /Billings MT

[cliffy49]

Planning a month or more this summer stopping at Sturgis for a couple of days during bike week and then up to Yellowstone for about a week.

Google gives me two routes from Spearfish to Billings. Either I90 (boring) or rt 212 going northwest. Both seem to be about the same as far as time goes, but one is going to be a total unknown for me.

I think I know what to expect taking I90 but have no idea about rt. 212. My question is has anyone taken this route and what could I expect if I go that way. Other than reservations I n W. Yellowstone, time is really not a concern so that to me is a wash between the two. This is my first trip west with the tt so really would prefer no long 6-7 degrees ( or more) hills if possible. Also, what are the services like along that stretch. Not absolutely certain of mileage pulling in the mountains, but would expect to get the average of about 8.5-10 mpg.

Thanks in advance for all your help.