To add to Kenny's point about GPS - you can purchase a cheap (compared to Navi) GPS with 2006 MS Streets & Trips +GPS. You need a laptop and for long trips an auto power supply. I bought one (MS St. & Trips) from Office Max for $130.00. It shows you where you are on the trip, lat. & long, speed, altitude above sea level, nearby attractions, etc. If you know the name of a business and a city,state - it will bring it up on the map with the street address and telephone #. This is very useful. It also has voice prompts to tell you if you go off - course and how far to turns. My laptop also has a DVD player which helps keep the kids busy on trips.

Good luck figuring your MPG.

 

Very good point.
Here in the Los Angeles basin (surrounded by mountains with some valley passes) we have some features that usually make the daily wind patterns predictable.
The sun warms the land in the basin and in the inland desert.
The the warm air rises.
The cooler air over the ocean moves in to take its place.

This regular pattern is evidenced by the presence of wind generators being located just before Palm Springs.

The 91 freeway goes though one of these generally East/West valley passes.
I think anyone traveling west on the 91 in the afternoon would usually be driving in to the wind.
Do you commute in this direction?
If not, then back to the drawing board.

 

The wind would normally be an issue with big gusts (santa ana winds) blowing through the canyon... but not so much this time of year. It's been pretty calm the past month or so (I'm very aware of this from my bicycling!).

As for altitude, I participated in "bike to work day" last Thursday, so I can attest to the fact that it's pretty flat the whole way from Anaheim hills to Cerritos. I do live on a big hill off the freeway, and I know I take a huge hit to MPG due to this, but my concern here was just the freeway portion.

By the way, you don't need a separate GPS to get elevations. The Navi system (assuming you have one!!!) can give you your latitude, longitude and elevation by just touching the screen at any point you desire.

 

It doesn't take big gusts. The difference between a 10MPH head wind and a 10MPH tail wind makes a noticeable FE difference.