New York — Oil futures settled lower Monday as a focus on US crude supply growth weighed on prices.

ICE April Brent settled down 59 cents at $61.51/b and NYMEX March WTI was 31 cents lower at $52.41/b at market close.

And diverging prompt-month WTI and Mars crude prices on the US Gulf Coast pushed the sweet/sour spread to $8.10/b Monday, S&P Global Platts data showed - the widest it has been since January 2014.

Mars, a Gulf Coast medium sour benchmark, has seen support in recent weeks after the US levied sanctions on state-owned Venezuelan oil company PDVSA. The de facto ban on imports of heavy sour crude from Venezuela has increased demand for other heavy feedstocks from USGC refiners scrambling to secure supplies.

Prompt-month Mars was assessed by Platts at $60.51/b Monday, up 49 cents from Friday's close and an 11-session high.

US crude production has averaged at a record high 11.9 million b/d so far in 2019, according to US Energy Information Administration data, but the bulk of this output is much lighter and sweeter than the Venezuelan crudes.

This record production likely contributed to a 2.7 million-barrel increase in US crude inventories to 449.9 million barrels in the week that ended Friday, according to analysts surveyed by Platts Monday.

While crude supply was expected to grow, an uptick in planned refinery maintenance is eating into crude demand and weighing on prices.

About 2.37 million b/d of US distillation capacity was slated to be offline for planned maintenance this week, according to S&P Global Platts Analytics data. While down from 2.59 million b/d offline last week, the scheduled maintenance comprises nearly 13% of total operable distillation capacity.

NYMEX product futures also settled lower Monday. March ULSD was down 1.63 cents at $1.8922/gal and March RBOB was 2.72 cents lower at $1.4192/gal.

Refined product stocks headed in contrasting directions last week, with gasoline inventories rising 800,000 barrels to 258.7 million barrels and distillate stocks falling 800,000 barrels to 138.2 million barrels, according to the analysts surveyed.

-- Chris van Moessner, christopher.vanmoessner@spglobal.com

-- Edited by Keiron Greenhalgh, newsdesk@spglobal.com