"I think oil has bottomed. I think we should be buying oil stocks," said Jim Cramer on Wednesday's "Stop Trading!" segment on CNBC. "The multiples are the lowest I've seen, and if oil stays in the $40s, these companies are going to make a lot of money."He specifically recommended Exxon ( XOM), ConocoPhillips ( COP), Terex ( TEX) and Occidental ( OXY). "I want that dividend," he said. Copper inventories "have been going down, down, down, down, down," Cramer said. "I believe that this is a sign that the Chinese stimulus is working. He said that Freeport-McMoRan ( FCX) "is ramping, and I don't think it's done." Caterpillar ( CAT) is experiencing a "big short-cover rally," Cramer said. That said, "You can't build roads and bridges without CAT, so maybe the money is going to start trickling down." Cramer said that people "confuse BJ's ( BJ) with Costco ( COST)." Whereas Costco sells avoidable products such as electronics and jewelry, BJ's "is much more staple, staple, staple." Costumers at BJ's and Big Lots ( BIG) can "buy cheaper products and more of them." Last night, Cramer said, Aecom ( ACM) "did a secondary at $20, and if you bought it, you're up a buck. When is the last time that happened?" He said it's an "extra signal that there's demand."