Honda Insight
 

Purchased 2020 Honda Insight Touring in July 2020 and was getting around 48 to 50 MPG average, then November came and temperature dropped to 60 degrees Fahrenheit (from 80-90), my MPG dropped drastically to 37, now it's about 20 degrees Fahrenheit and I'm getting 34 to 35 MPG. My driving hasn't changed. Is this normal? I called my service department and they said it was because of fuel additives they add during winter. My old Prius never had such a noticeable change, maybe 1-3 MPG difference.

I even tried 93 octane, but that made no difference.

Winter blend does have less energy. Then it does take longer for fluids, greases, and other things to warm up. The denser air will also mean more air resistance.

But that does sound like a bigger than normal drop. Check the tire pressures; they'll drop with the cold. Are you coming up to any required maintenance?

It happened around 2000 mile mark on the new insight. I'm now at 5000 mile mark. Tire pressures are all within normal limits. Oil change shows no change either.

The drop in MPG doesn't make sense to me.

I can't see any fuel entries on fuelly, are you using the cars computer read out or measuring the fuel economy correctly? The cars computers can often be inaccurate, although from experience, the Honda I had was highly accurate in fairness. See how your tank averages out, perhaps the reading is a short term figure, maybe resetting after each short journey? Have the nature of your journeys changed at all? Because hybrids can be awful on long highway stints, and are far better around town with lots of regen and low speed EV miles. I remember a review of a Yaris hybrid and it got similarly poor fuel economy when driven long distance on the motorway.

I created an account so I don't have any data on Fuelly yet. I'm using my car's readout but I also calculate with Trip A meter of miles over how many gallons I fill up at the gas station and the numbers are confirmed.

I had such a hybrid car and I know how difficult it is to find spare parts for such a car.

Yesterday I analyzed my answer again and realized that even if you look at the report on a free car by vin, you will see how long it took to repair. By the way, this information is provided by the Vininspect service. This app has a large hybrid car database.

Were you able to resolve your issue regarding the MPG drop?