The cost of oil fell 21.8% between May 1 and June 1 - from $106.50 to $83.23 a barrel - the sharpest monthly drop since December 2008.
A few analysts blame disappointing economic news and stagnant U.S. demand for the short-term decline.
But most think crude has now found a bottom and will likely head higher for the remainder of the year - perhaps a whole lot higher.
Actual oil price estimates range from a fairly conservative average of $104 a barrel, as forecast by the U.S. Energy Information Association (EIA), to a turmoil-driven possibility of $200 a barrel.
Either one represents a substantial profit opportunity for energy bulls.
However, chasing those profits by investing directly in oil can be both a costly and risky proposition.
The standard New York Mercantile Exchange (NYMEX) futures contract for West Texas Intermediate (WTI) crude represents 1,000 barrels of oil, worth roughly $84,000 at this week's prices.
That means a $1 per barrel change in oil prices means a gain or loss of $1,000. What's more, the initial margin requirement to purchase (or short) one contract is currently $6,210.
How to Invest in Oil Without Buying FuturesIf that sounds a bit rich for your blood, don't fret - there are several alternatives to futures.
The most attractive is one of the exchange-traded funds (ETFs) designed to closely track the changes in the price of oil.
These funds can be purchased through your regular broker - no commodity account needed - and you can get in the game with a 100-share lot for as little as $2,400 (or half that if you buy "on margin"), depending on the fund you choose.
At last count, there were 20 oil-price ETFs traded on U.S. and Canadian stock exchanges, and an equal number listed on the London Stock Exchange.
But be warned, many of them are fairly new and still lack the liquidity needed to be good trading vehicles. Some are better than others.
In fact, at least four of them have enough daily volume to allow easy entry and exit points, while also offering the potential for profit regardless of which way the price of oil moves.
The two most straightforward choices for a simple bullish play on oil are: