NEW YORK (TheStreet) -- In a recent interview Gary Heminger, the chief executive of oil refiner Marathon Petroleum (MPC - Get Report) , told Jim Cramer that the company may benefit further from the recent fall in oil prices as it could drive consumer demand higher, and the stock has already rallied as a result.

Nonetheless, the recent fall in the spread between Brent and WTI could shrink Marathon Petroleum's profitability in the coming months.

In the past month, shares of Marathon Petroleum rose by 16.7%, and shares of other oil refiners also benefited, with Valero Energy (VLO - Get Report)  rising by 10%.

U.S. refiners benefit from a larger spread as they purchase lower priced WTI crude and sell the refined products at prices determined by the Brent, the higher-priced European benchmark.

The chart below shows the changes in the spreads between Brent and WTI, Brent and Louisiana Light Sweet and Brent and Mars.

Source of data: EIA, Valero's Web site and OPEC

The fourth-quarter data are based on the changes in the spread during October and part of November.

All the spreads have contracted during the fourth quarter. If this trend continues, it could adversely affect Marathon Petroleum's margins in its refinery business, which still accounted for about 90% of its earnings in the third quarter.

The better-than-anticipated third-quarter earnings results also pulled up the company's stock. Its recent quarterly results showed diluted earnings per share of $2.36, 5 cents higher than analysts' consensus estimate. 

Marathon Petroleum benefited from higher spreads between Brent and WTI, as indicated below.

Source of data: Google finance and EIA

Moreover, Marathon Petroleum's refining and marketing margins rose to $14.55 per barrel of oil, a 57% spike, year over year.

In the third quarter, Marathon Petroleum's gross profitability grew to 7.1%, from 3.8% a year earlier. The company also recorded higher earnings from its Speedway unit, after acquiring Hess retail stores at the end of September.

Conversely, the company didn't increase its refinery throughputs as it remained at 2,155 million barrels per day in the third quarter, the same volume as a year earlier.

Looking forward, the U.S. Energy Information Administration still estimates the discount of WTI to Brent will slip to an annual average of $6 per barrel, nearly $1 lower than this year's average discount.

The EIA also projects that U.S. liquid fuels consumption will fall by 0.3% this year.

Based on the above, Marathon Petroleum may not necessarily benefit from the recent fall in oil prices.

Lower gasoline prices could drive higher the demand and increase Marathon Petroleum's revenue from other operations such as its retail subsidiary, Speedway. But if the spread between Brent and WTI remains low, this could slash the company's profit margin.

At the time of publication, the author held no positions in any of the stocks mentioned.

This article is commentary from an outside contributor, separate from TheStreet's news coverage.

TheStreet Ratings team rates MARATHON PETROLEUM CORP as a Buy with a ratings score of A. TheStreet Ratings Team has this to say about their recommendation:

"We rate MARATHON PETROLEUM CORP (MPC) a BUY. This is based on the convergence of positive investment measures, which should help this stock outperform the majority of stocks that we rate. The company's strengths can be seen in multiple areas, such as its solid stock price performance, increase in net income, attractive valuation levels, good cash flow from operations and largely solid financial position with reasonable debt levels by most measures. We feel these strengths outweigh the fact that the company shows low profit margins."

You can view the full analysis from the report here: MPC Ratings Report