Chicago's spot unleaded regular conventional gasoline prices soared on Thursday amid speculation of production cuts at BP PLC's oil refinery in Whiting, Ind. The speculation came after the company reported emissions to the U.S. National Response Center and an apparent outage of a key gasoline-making fluid catalytic cracking unit at Exxon Mobil Corp.'s refinery in Joliet, Ill

Chicago's spot unleaded regular conventional gasoline prices soared on Thursday amid speculation of production cuts at BP PLC's oil refinery in Whiting, Ind.

The speculation came after the company reported emissions to the U.S. National Response Center and an apparent outage of a key gasoline-making fluid catalytic cracking unit at Exxon Mobil Corp.'s refinery in Joliet, Ill.

A person familiar with operations at BP's 405,000-barrel-a-day refinery told Dow Jones Newswires that the plant was operating "smoothly," and others in the region said the emissions did not affect production.

Exxon Mobil Thursday declined to discuss day-to-day operations but had reported flaring at its 238,600 barrel-a-day refinery in Joliet, Ill., after a furnace shutdown on Sunday.

On Tuesday, Husky Energy shut down operations at its refinery in Lima, Ohio, for about 10 days of repairs at a furnace.

And on Monday, ConocoPhillips said its 306,000 barrel-a-day Wood River refinery in Roxana, Ill., would run at reduced rates "for several days" after a power outage on Saturday.

As such, Chicago's unleaded regular conventional gasoline for prompt, first-cycle July delivery rose to between 3.5 cents and 5.0 cents a gallon above the August Nymex gasoline benchmark price, up from discounts of between 0.5 cents and 1.5 cents to August Nymex on Wednesday, and up from a 9.0-cent discount a week ago.

Conventional-gasoline for oxygenate blending, or CBOB, for first-cycle July delivery in Chicago traded at a premium of 2.0 cents to August Nymex.

Group Three's discounts for regular unleaded gasoline delivered between July 1 and 10 narrowed to discounts of between 3.0 cents and 4.0 cents to August Nymex, from discounts between 4.0 cents and 4.5 cents to August Nymex the day before.

In the Gulf Coast, M2-grade regular conventional gasoline for prompt, 38th-cycle delivery last traded at a 12.0-cent discount to August Nymex, and traded at Wednesday's high of 10.75 cents under August Nymex earlier on Thursday.

Same-cycle M1-grade traded within Wednesday's ranges, at a 5.05-cent discount to August Nymex.

Ultralow-sulfur diesel fuel, or ULSD, for delivery on the newly-prompt 37th-cycle, which prices against August Nymex, traded between premiums of 3.65 cents and 3.9 cents to August Nymex, and barrels for 38th-cycle delivery traded at premiums of 3.8 cents and 3.95 cents to August Nymex.

Heating oil for prompt, 37th-cycle delivery traded at a 4.25-cent discount to August Nymex and compares to deals done at 3.75 cents and 4.05 cents below August Nymex on Wednesday.

And prompt, 37th-cycle jet fuel traded within recent ranges, at between premiums of 4.8 cents and 5.5 cents to August Nymex.

New York's F2-grade reformulated-gasoline for oxygenate blending, or RBOB, for prompt July delivery traded at a premium of 9.75 cents to August Nymex, while barrels for ratable-July delivery, which means a delivery will be made in each of the three 10-day periods of the month, traded 0.25 cents down on the day, at a 3.75-cent premium to August Nymex.

328-grade CBOB for prompt shipment on the Buckeye Pipeline traded at a 6.0-cent discount to August Nymex, and barrels delivered by July 10 traded 0.25 cents to 0.35 cents up on the day, at a 6.75-cent discount to August Nymex. And the July 20 timing traded at a discount of 8.5 cents to the August screen.

ULSD for prompt July delivery traded at a premium of 9.75 cents to August Nymex heating oil futures, and heating oil for 32nd-cycle off-line Colonial Pipeline delivery traded at a premium of 0.5 cents to August Nymex.

The August Nymex heating oil contract settled 1.16 cents above Wednesday's settlement, at $2.9463 a gallon; the August Nymex RBOB contract settled 3.43 cents up on the day, at $2.9692.