NEW YORK ( TheStreet) -- I was talking to Jim Cramer about the relative strength of oil stocks and where to invest in this very volatile time. There is an old trader's axiom that says you should always look to buy strength and sell weakness. Never has that rule seemed as obvious as right now with the higher-beta exploration and production oil stocks such as Anadarko ( APC), Apache ( APA), Noble Energy ( NBL) and EOG Resources ( EOG). All of them have exhibited tremendous strength in the last several days, despite a major market shakeout. And there are reasons why all of these stocks should remain strong and why you should look to adjust your portfolio towards these names now. First, crude oil prices have remained expensive despite a major selloff in virtually every other asset class, including stocks, bonds and most other commodities. Second, these exploration and production oil stocks are not reliant upon their dividends for their valuations, and are more cyclical in their price action and therefore are less sensitive to big bond-market fluctuations. Oil is the most "staple-like" of the hard assets and represents a defensive sector in an equity market under siege. All four of the companies I highlight share all of the important characteristics we're looking for in a "defensive" oil name. None relies upon its dividend for valuation. All are large-cap players with market caps between $25 billion and $45 billion. All have acted very strongly in the last week since the end of the latest FOMC meeting. Where they diverge is in their specific areas of production. I do a deeper dive in understanding the similarities and differences between these four exploration and production companies and my thinking behind investing in them now with Jim in the video above. At the time of publication, Dicker owned shares of NBL and APC.At the time of publication, Action Alerts PLUS, which Cramer co-manages as a charitable trust, had no positions in stocks mentioned.