I am averaging 42.7 MPG on my way to work. I am averaging 37.6 MPG on the return trip. All highway. My cruse is set to 65 both directions. I cannot detect a difference in the road grade coming or going.

I am in beautiful Dayton, OH. There is probably a 15 to 20 degree Fahrenheit temperature drop from the time I go to the time I leave. I am not using front or rear defrost either direction. Not cold enough yet. I am not letting the car warm up before leaving. Fresh air circulation instead of recirc to help keep the windows defrosted.

 

I'd be willing to bet you're driving slightly uphill. Test it by driving to work then immediately back in the dead of night where the temperature will remain mostly constant.

 

5 MPG difference for a slight grade difference? I've posted several times about the wonky wide swings in fuel economy I continue to see with my car, and have seen similar reports from others. I haven't been able to pin them down to anything specific yet. Colder temps do seem to have a correlation, but not always.



Note the 11/28 and 11/29 MPG numbers. Both interstate driving in similar road and ambient weather conditions (including temperature). 32 vs almost 38…

Odd.

es

 

If your on cruise control both directions, you should be able to monitor ECON next to your speedometer (green or blue), and determine if grade is the issue. The cruise control will force your acceleration if your traveling uphill, and will be reflected in your RPM and your efficiency.

 

Everything plays a part. Temperature, winds, traffic, elevation- even how many lights you may have to sit at on each route. Wikipedia shows Dayton is actually 40 feet higher than West Carrollton. Check online for topo maps of your route to see just what you're working with.

I looked at your posts and saw you came here from a 99 Corolla- EPA combined 26 mpg. Even if you had mpg instrumentation in it, a 2-3 mpg variation on your commute may not have seemed all that noticeable. But by the time you extend that to 40 mpg and have a display waving your trip mileage in your face, not only is that small percentage variation spread over more mpg, but the car is also constantly calling your attention to it. I wouldn't worry about it, just use it as a chance to see roads and traffic in an entirely new way.

 

Interesting, Charlie! Thanks for the investigation. The trip is actually between West Carrollton and WPAFB. If I am reading it correctly it would appear that WPAFB is 121 feet higher than West Carrollton. This would seem to indicate the opposite of what I am getting.

You are correct though. I am happy either way

 

Just looked at that on Google Maps. Assuming you're using I-675, you're driving somewhat with the prevailing wind going to work and against it coming home.

 

When it rains while your driving to work, does the rain come straight down, or does it fall slightly to the side? Nothing worse for your MPG than driving against the rain.

 

Drivers side or passengers side. Would it help to lean into or away from the rainfall?

 

Thanks Fitmo, I am sure any wind would have significant impact. Not a lot I can do about that. I have found the whole thing interesting. I am loving the ride and mileage.