Fuel economy drops in winter

At your next visit

General guidance for this symptom. A warning light that is flashing or an overheating engine: stop driving and call.

Likely causes

• Cold engine and short trips

  Engines run less efficiently until they reach operating temperature. fueleconomy.gov notes that short trips in the cold are where mileage suffers most.

  Full-service oil change
• Low tire pressure

  Air pressure falls as the temperature falls. Underinflated tires increase rolling resistance. Our maintenance check includes tire pressure, set to the placard on the door jamb.

  Multi-point maintenance check
• Oil heavier than specified or long past due

  Thick oil adds friction at cold start. Using the grade your manual lists, often a 0W or 5W grade, helps the engine warm up efficiently.

  Full synthetic oil change
• A clogged air filter or dirty fuel system

  These matter less on modern engines than people think, but a badly restricted filter or heavy deposits can make a small difference worth recovering.

  Engine air filter

Cold weather costs fuel in several ways at once. A cold engine runs richer until it warms up, cold oil and gear lube create more friction, winter fuel blends carry slightly less energy, tires lose pressure, and the heater, seat heaters and defrosters add load. On short trips across town, the engine may barely reach temperature before you park. In Minden, about 75 nights a year fall to 20 F or colder (NOAA 1991-2020 normals), so the effect is real in the Carson Valley.

At a glance

• Some winter drop is normal; fueleconomy.gov cites roughly 15 percent in city driving at 20 F
• Short trips cost the most because the engine stays cold
• Tire pressure drops as temperatures fall
• The oil grade in the manual is the one the engine was designed around
• A sudden, large drop is a different problem worth checking

What is normal and what is not

A gradual drop of a few miles per gallon as fall turns to winter, more on short trips and less on highway runs, is normal. A hybrid's drop can be larger, because the engine runs more to keep itself and the cabin warm; fueleconomy.gov cites a larger winter loss for hybrids than for conventional cars.

A sudden, large drop is different. If mileage falls off a cliff in a week, or comes with a check engine light, rough running or a fuel smell, something else is going on. Our poor fuel economy page covers the year-round causes.

Habits that help

• Combine errands into one trip so the engine stays warm
• Skip long idle warm-ups; drive gently after a short wait
• Park in a garage when you can
• Check tire pressure on cold mornings, not after driving
• Remove roof racks and boxes when you are not using them

These come from the cold weather guidance on fueleconomy.gov, run by the U.S. Department of Energy and the EPA.

What we can do in the bay

Our full-service oil change uses the grade your owner's manual specifies, and we check and set tire pressure to the placard as part of the visit. We pull the engine air filter and show it to you, and check the other fluids. None of that changes the weather, but it removes the avoidable losses.

If you are noticing a large drop together with a running problem, we will tell you what we see, and anything beyond our services goes to a repair shop.

Before your next winter trip

Reno averages about 122 nights a year at or below freezing (NOAA 1991-2020 normals). A pre-winter visit covering oil, tires, wipers, battery and coolant handles most of what cold weather asks of a car. Our before-winter checklist lists it all.