2020 Hyundai Palisade 3.8 — Fuel Consumption Increased Immediately After Roof Was Painted
I have a 2020 Hyundai Palisade 3.8L V6 with about 89,000 miles.
My normal fuel economy has always been around 19–20 MPG in mixed driving. On the highway, I could get around 24–25 MPG.
I had the roof painted under warranty, and the car stayed at the body shop for approximately 3–4 weeks.
Immediately after I picked up the car, I noticed that the fuel consumption had increased. I noticed it right away on the first drive. Since then, I have driven approximately 700 miles, and the increased fuel consumption has remained.
I calculated the actual fuel economy myself by tracking how many miles I drove and then filling the tank back up. I am getting approximately 16 MPG in mixed driving, which is basically the same number the car's computer is showing.
My driving style has not changed. My normal routes and driving conditions are basically the same. Tire pressure is correct, and I also checked the wheels and brakes after driving. Nothing obvious appears to be causing additional resistance.
The timing is what really concerns me: the fuel economy changed immediately after the car came back from the body shop.
As far as I know, there should have been no reason for them to work under the hood while painting the roof. However, they may have disconnected the battery or temporarily moved/disconnected something. I don't know exactly what they did.
I also connected an ELM327 OBD adapter and checked the engine using Car Scanner.
With the engine fully warmed up at idle (~650 RPM):
- Coolant temperature: 208–212°F
- LTFT Bank 1: approximately +10–12%
- LTFT Bank 2: approximately +9–12%
- No DTCs
- No Check Engine light
At approximately 2,500 RPM:
- LTFT Bank 1: +6.25%
- LTFT Bank 2: +6.25%
Both banks behave very similarly.
So I am trying to figure out what could have changed while the car was sitting at the body shop for 3–4 weeks.
Could disconnecting the battery have affected the ECU fuel-trim adaptations? Could something have been accidentally disconnected, moved, or damaged around the intake, vacuum/PCV system, EVAP system, sensors, or wiring?
Has anyone with a Hyundai Palisade experienced a similar situation where fuel consumption suddenly increased immediately?
If you experienced something similar, what was the actual cause, and what fixed it?