Struggling going uphill in Rockies Colorado

hello, i just did the drive you are doing, 04 155k, 8000m trip in 21days, jellystone it got 65mpg for 426 miles. get a run at the hills then just enjoy the scenery, slow up quick down, 57mpg average, here in socal only 44to48mpg. i did put 91 ethenol free in once, I DID notice the difference. last time 1977 my 69bug, had to rejet carb, vapor lock issues, and killed motor. enjoy your vacation!!!

 

I personally just set the cruise at the speed limit (traffic and weather permitting) and let the car do its thing. I average ~48MPG on the trip from El Paso, TX to northern Utah (and back) doing the speed limit according to my GPS with cruise. Many hills and I would say its over half at 75MPH with the rest mainly at 65MPH.

 

As others have said, the trick is to not let the battery discharge to 2 bars.
I gain speed before the hill and then go up at ~ 2500 - 3000 rpm without a problem. I might have to climb a little slower than some other vehicles, but so what.