Winter is where changing your oil is really important. During winter with short trips, your engine does not get up to operating temperature, allowing condensation to collect in the oil. Make sure to take the car on a longer driver and get it fully up to operating temp once in a while to help burn off that moisture. If you remove your oil cap and see a white slime, that is condensation from all the short trips. Short trips can be extremely hard on your engine, depending on the make or model.
Also, almost every "conventional oil" is a syn-blend now days due to the SN+ requirements. If you're changing your oil every 3,000 or 6 months, there's no real benefit to full "synthetic" unless its extremely hot or cold, or harsh operating conditions. My eco-boost F-150 gets full synthetic and 5K, once a year oil changes due to towing. The focus gets full synthetic at 12,000 mile/1 year interval (I've done a UOA so, I'm good to go with that mileage with some life to spare).
Condensation example from winter.