Weak manufacturing data from China and a US economy deemed to have "significant downside risk," saw benchmark North American crude futures drop more than $5 to just above $80 a barrel, bringing the discount to international oil prices to more than $25. The biggest oil sands player, Suncor Energy (TSE.SU), tumbled 6.8% to C$26.21 on the Toronto Stock Exchange, bringing its year to date losses to more than 30%. Canadian heavy oil – all of which goes to the US – sells for $15 less than US crude, meaning oil sands developers have to deal with an effective oil price of $60-$70 a barrel that puts at risk many of the $100 billion of projects on the go in Alberta.