EPA says 32 combined. You’re getting 27. Your car isn’t broken — the sticker was built on a dyno running a specific script, and your script is different. The typical gap is 10–15% below EPA, and the reasons are predictable.
What EPA actually measures
Five standardized drive cycles run on a chassis dyno in a controlled lab: city, highway, high-speed, A/C on, and cold start. The sticker blends them and applies a downward correction factor to approximate real driving — but the corrections haven’t kept up with how people actually drive (faster, with more acceleration, and climate-controlled).
What chews through your MPG
- Speed — aero drag scales with speed squared. 75 mph uses roughly 25% more fuel per mile than 60 mph. Single biggest factor on highway trips.
- Hard acceleration — fuel economy is about momentum. Every jackrabbit start burns fuel you’ll immediately brake away.
- Cold starts — the first 5 minutes of driving from cold can use double the fuel per mile of a warm engine.
- Short trips — if most trips are under 15 minutes, the engine is cold for a big fraction of the miles.
- A/C and heat — A/C costs 3–10% depending on conditions. Electric cabin heat in an EV is much worse (~20–30% of range in cold weather).
- Cargo and roof racks — an empty roof rack alone can cost 2–5 MPG.
- Tire pressure — 3 PSI low costs ~1% MPG. Check monthly.
Planning adjustment
For budget and trip-planning math: use EPA combined × 0.9 for mixed driving, × 0.85 for mostly-city or aggressive driving, × 0.95–1.0for long, gentle highway runs. Whatever you use, confirm it by tracking 3–4 tanks yourself — the real number for your car and your route is knowable.
Miles driven + gallons at fill-up = your actual MPG. Over a few tanks you’ll have a number more useful than the sticker.