Urals oil, Russia’s benchmark export crude, fell to the lowest price in six months as weakening refining margins reduce demand and increasing OPEC production boosts supplies of alternative oil types.

Urals traded at $1.08 per barrel less than Dated Brent on Friday, compared with a discount of $1.05 on Thursday, according to data compiled by Bloomberg. That’s the biggest discount since May 8.

“A lot of refiners are trying to run down stocks as far as they can, and we see very weak margins,” said Alexander Poegl, an analyst at JBC Energy in Vienna. “In addition to weak demand, you have more medium sour crude coming out of OPEC.”

The Urals price in the Mediterranean also declined. A cargo for delivery in Augusta, Italy, cost 92 cents less than Dated Brent, compared with an 88 cent discount Thursday. That’s the biggest discount since May 19.

Demand for Urals, a so-called medium sour crude type, has dropped as the profitability of turning the crude into products such as gas oil and fuel oil remains close to negative.

The refining margin for cracking Urals in Northwest Europe was 67 cents a barrel Thursday, according to Bloomberg estimates. It has averaged 42 cents over the past month.

Rising supply of crude from the Organization of Petroleum Exporting Countries is also crimping demand for Russia’s export blend because it is a similar quality to Urals and offers a better value for refiners, according to Poegl.

“Their hunger for other sour crude types such as Urals is less,” he said. “OPEC’s continuously weaker compliance adds more medium sour crude into the market.”

OPEC oil production rose for a seventh month in October, as compliance with output quotas dropped, the producer group said in a report last week.