* Midwest gasoline falls with driving season over
* Gulf Coast gasoline steady as supply up (Updates with end-day prices)
Sept 21 (Reuters) - Gasoline differentials in the Midwest extended declines on Wednesday on sluggish autumn demand, traders said.
Group Three gasoline fell half a cent per gallon.
"It is that time of the year for gas basis to go lower," a Midwest trader said.
Chicago gasoline differentials, which shrank by more than a penny per gallon in early trade, rallied in the afternoon and ended 0.75 cent higher.
Group Three ultra-low sulfur diesel differentials held close to recent highs despite pressure from steep discounts in the Chicago and well-supplied Gulf Coast markets. Chicago ULSD fell 0.75 cent a gallon.
Gulf Coast ULSD differentials slipped half a penny per gallon on Wednesday, while M3 gasoline differentials held steady after the U.S. Energy Information Administration said Gulf gasoline stocks surged by 1.69 million barrels last week. [EIA/S]
Midwest gasoline stocks also showed a significant gain of 1.2 million barrels, and both markets drove the overall increase in U.S. gasoline stocks by 3.29 million barrels to 214 million barrels.
East Coast gasoline inventories slipped by 186,000 barrels, the EIA said.
In the New York Harbor on Wednesday, RBOB and conventional gasoline barrels were bid lower with few trades reported despite the shutdown of a regional pipeline after it spilled up to 80 barrels of gasoline.
Buckeye Partners (BPL.N), which operates the line, did not say when operations will be restored on the ruptured 10-inch (0.25 meter) wide Auburn-to-Rochester line in New York state. [ID:nWEN8478]
The EIA said U.S. distillate stocks fell by 874,000 barrels to 157.6 million barrels, the EIA said. Midwest stocks gained 201,000 barrels, followed by a 120,000-barrel gain in East Coast inventories and a 20,000-barrel drop in the Gulf Coast.
All three markets east of the Rockies had higher refinery utilization last week, pushing overall U.S. utilization up by 1.3 percentage points to 88.3 percent, the EIA said.
The Midwest region showed the largest jump in utilization, up by 3.7 percentage points to 95 percent, reflecting Marathon Petroleum Corp's (MPC.N) restart of a gasoline-making fluid catalytic cracking unit at its 212,000 barrels-per-day (bpd) refinery in Catlettsburg, Kentucky. [ID:nS1E78B13P]
East Coast utilization was not far behind, as utilization in the region rose by 3.6 percentage points to 79.1 percent, reflecting continued ramp-ups in the aftermath of Hurricane Irene in late August.
Gulf Coast utilization climbed 1.1 percentage points to 89 percent last week, reflecting the wrap-up of some planned work at Exxon Mobil Corp's (XOM.N) 560,640 barrels-per-day (bpd) refinery in Baytown, Texas, the nation's largest.
For refinery news, please go to [REF/OUT]
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Cycle 54 M3 gasoline was seen done at 5.00 and 5.25 cents under October RBOB futures, unchanged from Tuesday's levels.
Newly prompt Cycle 54 61-grade ultra-low sulfur diesel was seen done at 0.25, 0.45 and 0.50 cents over the October heating oil screen, down half a penny.
Cycle 54 54-grade jet fuel was seen done at 0.55 and 0.60 cents over, down a quarter cent.
Scheduling Cycle 54 heating oil was flat at 4.25/3.75 cents under.
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Conventional M3 gasoline rose a quarter cent to 4.00 cents above futures.
M2 gasoline for cycle 50 was talked at 6.00 cents over, with no trades reported, and prompt M3 was seen about a half cent weaker, bid at 3.75 cents over.
Prompt F4 RBOB was offered 0.75 cent lower at 1.50 cents over while barrels for delivery on the Sept. 25 were seen slightly higher at 0.35 cents over.
Any-month F4 RBOB gasoline fell about 0.10 cents and traded at 0.50/0.25 cents under.
Prompt V4 gasoline rose to 26.00 cents over futures.
Prompt ULSD fell a quarter cent to 4.25 cents over and low-sulfur diesel was seen at 0.50 cents over, flat to Thursday levels.
Jet fuel talked some 0.50 cents higher at 4.50/5.00 cents over.
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Cycle 3 Chicago gasoline held steady to late-Tuesday levels at 1.00 cents under October RBOB gasoline futures while Group Three gasoline traded even to October futures, about a half cent lower than levels seen Tuesday.
Ultra-low sulfur diesel in Group Three was within range at 5.50/5.85 cents over October heating oil futures while Chicago ULSD fell 0.75 cent a gallon to 0.50 cents over futures. (Reporting by Kristen Hays in Houston and Selam Gebrekidan in New York; editing by Jim Marshall)