52 mpg in the morning, 58 in the afternoon

That temperature difference is likely more than enough to account for the difference. Good results on either leg, regardless -- well above the new EPA numbers. Congrats!

 

I agree. Great mpg numbers in the warmer parts of the US. Two days ago, we had a warm spell and my mpg jumped up to 49 . I still have three pips on the fuel gauge until my next fill up. Hopefully this tank will be my best in terms of mpg.

 

I'm out in Seattle, where the temperatures are pretty mild. But the hills take a beating on my mileage. I recently found a route that has slower speeds and more gradual hills, and it improved my mileage. I too notice a consistent difference between my morning & evening commutes. But the morning one is better. It's something like 56 vs 52 mpg. What I think is causing the difference is the way the hills are set. The morning route has long stretches of gradual downhills. So on the return trips I end-up with long stretches that tend to turn the ICE on. The route is mostly 40 mph, but with a fair amount of traffic lights.

So I guess I'm saying it could be terrain related too.

 

Here in the Chicago area it's been COLD. This morning when I left it was -2F and I got 38.4MPG on the way in. This afternoon it 'warmed' up to 14F and I got 53MPG.

The other week when it was in the low to mid 30's, I was seeing 56.1MPG.

 

WHAT??? fifty-something?? Man, its winter time and I'm getting 45.6 and I have to be happy about it!! (forced smile)

 

I've carefully monitored and documented the temperature effect on mileage:

 

Very nice work!

Rob

 

The higher outdoor temp helps in two ways:
1. it lets the engine reach optimal operating temperature sooner
2. it increases tire pressure, and harder tires have less rolling resistance

 

Outstanding MPG! I know the route quite well. Do you take the 5 freeway? What is your average speed? Do you use cruise control? In short, tell us your technique. I'm impressed.