Weird. If your RPMs increase during these slow downs then it’s from engine braking.

It could be that your car is downshifting for the uphill and then remains in that lower gear for the downhill, causing unintentional engine braking.

Are you using cruise control to set the speed? If so, it could be engine braking to keep it at the desired speed. Some cars do this, some don’t.

I used these a bunch in some jungle training. Any petroleum based jellies worked great, so we used bacitracin packets as our additive.

Fun fact: dead bamboo will always be dry in the middle between two joints. You can split it up into a couple thin pieces and it makes great kindling.

Live bamboo will create a small pressure bomb.