U.S. oil futures were slightly lower Tuesday after Norway blocked a labor shutdown of oil production that would have cut supplies. Crude oil was down 78 cents on the New York Mercantile Exchange to $85.21 per barrel. Home heating oil futures were down 0.88, or 0.32 percent, to $2.7402. Reformulated blendstock gasoline fell to $2.7653 per gallon. Natural gas for August delivery was down 7.1 cents to $2.812 per million British thermal units. At the pump, the national average price of unleaded gasoline was down slightly to $3.381 per gallon Tuesday, AAA said.