Tire pressure drops even without a change in temperature due to permeation, about 1psi a month but you also lose about 1psi for every 10ºF drop in temp at passenger car pressures. So if you haven't checked your pressures in two months and the temps have dropped 30ºF then you could be down by 5psi or more. Some tires permeate more than others. Winter Tech Information - Air Pressure, Temperature Fluctuations
Its more than just winter fuel blends. Running higher octane has been beaten to death as a waste of money on vehicles that don't specifically require it (forced induction/highly modified members disregard).
"Cold weather affects your vehicle in more ways than you might expect:
Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
Heated seats, window defrosters, and heater fans use additional power.
Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.
Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.
Tire pressure decreases in colder temperatures, increasing rolling resistance.
Winter grades of gasoline can have slightly less energy per gallon than summer blends.
Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. This also affects the performance of the regenerative braking system on hybrids."