I've traveled through Canada many times but have only had a walk through about 3 times in 4 years. Last one was yesterday. The agent opened every car ahead of us and confiscated a bag of citrus from the one ahead of us. This was the American side in Port Huron. She came in our motor home and opened the refrigerator, bathroom and just seemed to be looking for humans as she didn't open any compartments or cabinets. The refrigerator was more like opening it to make sure it was actually a refrigerator.
Traveling through I now have a policy of fueling up before I enter and only after I exit Canada. I stopped at an Esso on Oil Heritage Rd. at 402. The guy wouldn't let me pay at the pump. So I filled up and then he told me that he can't take American credit cards unless I call them before hand and tell them that I am going to use it in Canada. So I ended up having to give him most of my cash and he told me the exchange rate is .05 in his favor. BTW it was supposed to be .05 in my favor. This is the first time this has ever happened in Canada. I camp in Canada frequently and everyone takes my credit card.