What happened The cost of shipping oil around the world is on the rise this week, and if you think that might be good news for oil tanker stocks, you're right! As of 3:20 p.m. EST Wednesday, shares of Nordic American Tankers (NYSE: NAT) are up a strong 8%, Teekay Tankers (NYSE: TNK) is up 10.5%, and Scorpio Tankers (NYSE: STNG) is up 11.4%. Image source: Getty Images. So what Not all "tankers" are created equal, of course. Nordic American focuses its efforts on the transportation of crude oil, while Scorpio transports primarily refined petroleum products, and Teekay does both. The good news for these stocks, though, is that no matter what they transport, the prices they can charge for transportation are going up. According to the latest data out of Lloyd's List, after a slump that began in January, both the "clean" (refined petroleum) and "dirty" (crude oil) indexes have been rising over the past several days. From a 2021 low of 478, the Baltic Clean Tanker Index (BCTI) was up 5.2% yesterday, and the Baltic Dirty Tanker Index (BCDI) was up 4%. Now what All three stocks are up much more than 4% or 5% today, of course, and that may seem disproportionate to the gains racked up in the indexes -- especially given the tenuous state of the companies' balance sheets. Nordic American, for example, is carrying more than $350 million in debt on a market capitalization of just $480 million, while both Teekay and Scorpio carry debt levels considerably higher than their respective market caps. Investors, though, I suspect, are betting that the gains we've seen over the past week are just the beginning of a resumption of the longer-term trend of rising prices for oil transport that began last summer. If they're right about that, then the gains oil shipping stock investors are enjoying today could be just the start of the good news. 10 stocks we like better than Teekay TankersWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Teekay Tankers wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Rich Smith has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source