[Motor31]

I use cruise control all the time including in the mountains. Then again I have a very large tow vehicle too. I get the best mileage that way and only drop out of cruise if the mountain grade is better than 6% on secondary roads. I do drop out of cruise on the back side and use the exhaust brakes as well as down shift.

If you are finding the truck is "hunting" or shifting between overdrive and the next gear down, drop out of cruise and hold it in the lower gear. Down shift on the back side of mountains / hills as well to help with braking especially if you do not have an exhaust brake.

Watch your temperature gauge and slow down if you are getting hot. I hope you also have a transmission temperature gauge as well. That can save you from having to replace the fluid often or get a transmission rebuild early. Make sure you have a good and large transmission oil cooler too, assuming it's an automatic transmission truck.