Demand for diesel and jet fuel will help push oil prices to $90 a barrel in 2020, according to Morgan Stanley.

The investment bank previously forecast Brent would average about $65 in each of the four quarters of 2020. Brent hit a three-and-a-half-year high at $79.47 a barrel on Tuesday. It hasn't risen above $90 a barrel since October 2014.

But Morgan Stanley warns that stockpiles of middle distillates, which include diesel and jet fuel, are nearing five-year lows as demand for the fuel grows. Refineries around the world are now struggling to keep pace with consumption, it says.

"Over the next few years, we expect tightness in one particular product — middle distillate — to lead to strength in one particular liquid, crude oil, and especially those crudes that look like Brent," Martijn Rats, Morgan Stanley's global oil strategist, said in a research note on Tuesday.