Well it's been cold as hell lately, I'd imagine you let the car sit and warm up for a bit, obviously it takes longer for the car to reach operating temps in cold weather that in turn uses more fuel (short little trips furthers that problem), did I mention it's cold.
Few things you can do to help are plug the car in at night, hope you have a block heater. That reduces the time it takes the car to reach operating temp saving fuel. Will also put less strain on the starter being the oil will also be just a smidgen warmer, minute radiant heat.
Put something in front of the radiator to block the cold. I just have a chunk of cardboard in front of mine zip-tied in place. Leave about the bottom 2 rows of the radiator uncovered though or poke a few random holes in the covering. It does need some flow still.
Keep a close eye on tire pressure. Air contracts in the cold and tires will sometimes go flat simply from the rim shrinking a bit.
Could be other factors but the cold is playing a big part right now.