Formula
The combined figure is a weighted average:
combined = (city × city share + highway × (100 − city share)) / 100
Both inputs are miles per gallon. The fuel economy page measures one tank. It does not blend two cycles.
Assumptions
- City and highway are both miles per gallon.
- The city share is the percent of distance, not of time.
- The rest of the distance uses the highway figure.
Worked example
22 mpg in the city and 32 mpg on the highway, with 55% of the miles in the city, combines to 26.5 mpg.
Input definitions
- City share
- The percent of miles driven in the city cycle.
- Combined economy
- The distance-weighted miles per gallon of the two cycles.
Limitations
A manufacturer's city and highway numbers are test cycles. Your road will differ. This page does not convert to liters.
Questions
Is this the same as one tank?
No. One tank is the fuel economy page. This page mixes two economies you already have.
What if every mile is highway?
Set the city share to 0. The result is the highway figure.