Can it be that only a month ago we included two refiners in our Best Buys list? Yes, it can, even if a month can seem like an eternity in energy investing.

Since that call, the refining stocks in question have pulled back from the vicinity of record highs amid broader market turmoil.

We now believe there’s worse to come, which is why we’re urging subscribers to reduce exposure to this sector.

For much of the year to date, refining margins have been abnormally high, boosted by a combination of heavily discounted domestic crude and near-record gasoline demand as a consequence of lower pump prices.

More recently, the margins (known in the industry as crack spreads) have regressed, hardly unexpected with the summer driving season now over. And while share prices have pulled back as well, they haven’t pulled back enough given the rising risks of a refining slump.

This volatile industry suffers more than its fair share of those, and the next one could be worse than the stretch between May and October of last year that saw Valero (NYSE: VLO) drop 25% and Marathon Petroleum (NYSE: MPC) 21%, peak-to-trough.

Then, the problem was triple-digit crude and sluggish fuel demand dampened by the high prices. Now crude is cheap and gasoline demand high, but both of those trends are getting long in the tooth. And the refiners have far more to lose this time around once those tailwinds reverse.

No one, of course, knows exactly when that might happen. But it’s only a matter of time, for a couple of reasons. One is that crude won’t stay at $45 much longer in the absence of a global recession that’s not in the cards – that price is just too low to produce satisfy the ongoing growth in demand for long.

The other threat is from heavy Middle East and Asian investment in new refineries, which are already dampening the boom in U.S. fuel exports over recent years. U.S. refineries ran all-out this spring and summer to process discounted crude — as did many of their overseas rivals. The result is that some of the recent crude glut has been transformed into a surplus of diesel now selling below the price of gasoline. And while gasoline demand has been running at record levels in the U.S., it can’t be expected to keep growing now that lower fuel prices are no longer a novelty.

The trends responsible for recent refiner outperformance are under growing strain as oil producers retrench, automakers continue to improve their vehicles’ fuel efficiency and new overseas refineries compete aggressively for market share.

Refiner share prices owe a lot to the events of the past year. And yet as shale drillers have proven over that span, investing in energy stocks based on the fundamentals that soon may not apply can be very, very costly.

Refiners stocks won’t necessarily suffer an implosion of shale proportions: that’s the worst-case scenario and hardly the most likely. But it’s difficult now to see where the additional upside will come from, given the likelihood of more expensive crude and an increasingly competitive refining market that’s unlikely to sustain its recent growth rate.

As a result, we’re recommending the sale of CVR Refining (NYSE: CVRR), Marathon Petroleum (NYSE: MPC) and Western Refining (NYSE: WNR).

We’ve continuing to recommend refinery logistics MLPs Delek Logistics Partners (NYSE: DKL), Holly Energy Partners (NYSE: HEP) and PBF Logistics (NYSE: PBFX), which are shielded from short-term margin volatility by long-term, inflation indexed shipping contracts. Top ranked Best Buy Magellan Midstream Partners (NYSE: MMP), Genesis Energy (NYSE: GEL) and Global Partners (NYSE: GLP) should also be able to cope with their limited exposure to refining throughputs.

(NYSE: GLP) should also be able to cope with their limited exposure to refining throughputs.