[obermd]

Fairplay to Bailey, Colorado

My best "flat" 25 mile fuel economy is just over 60 MPG.

 

[obermd]

In mountains could be partially due to elevation changes ? :not_worthy:

It was but it wasn't all downhill. That run was from the Shell station in Fairplay to the Conoco in Bailey. While a lot of downhill there are two passes (Red Mountain Hill and Kenosha Pass) between them I was above 50 MPG at the top of Kenosha which is about the mid point on that segment. That's why I also posted that I've seen ~60 MPG on "flat" ground for 25 miles.

About a year and a half ago I drove from my home on the south side of Denver to the University of Wyoming in Larimie, WY and back. I took the same route in both directions which eliminated elevation changes in the fuel economy calculations and still ended up on the high side of 52 MPG for the day.

The ECO MT really, really likes altitude and hills. I get 1-3 MPG improvement in overall fuel economy in Colorado than I do when driving the car in the east.

 

[obermd]

Impressive, Obermd!!! Did you ever get a chance to do a check from Eisenhower to the twin tunnels?

Unfortunately not. I did take a road trip this fall and managed 49.5 MPG over 500+ miles through some serious mountain passes, including the one between Creede and Lake City where I had to use 1st gear going up and coming down due to the steepness and sharp turns. http://www.cruzetalk.com/forum/27-fuel-economy/177089-she-likes-mountains.html.

Here's my report going up to the University of Wyoming: http://www.cruzetalk.com/forum/27-fuel-economy/114201-eco-mt-65-mph.html. I have corrected my earlier post in this thread - 52 MPG, not 55 MPG. I do remember hitting I-25 on the way back at 60 MPG because of the long downhill stretches on US 287. From that thread:

25 mile best: 2.4 L/100 KM => 98.0 MPG with possible range of 96.0 to 100.1 MPG
50 mile best: 3.0 L/100 KM => 78.4 MPG with possible range of 77.1 to 79.7 MPG

 

[obermd]

Interesting, the super-high economy in the mountains. I noted this too, on my 2001 Sentra 5MT, 1.8 naturally-aspirated port-injected engine. At home at 600 ft, most tankfuls are 35-40. 40 and better if it's summer and if I'm really trying with 60 mph highway speeds, etc. When on trips in the mountain west, was seeing 45 mpg and better without really trying, iirc.
Guesses: 1. Gasoline may be straight, no ethanol. 2. Mountain driving simulates the pulse-coast strategy, with full-throttle hauls upgrade, and fuel cutoff coasting downgrate. 3. Less wind resistance at altitude 4. Less pumping loss because at altitude, more of the driving is done with wider throttle settings due to the thin atmosphere.
Edit: Guess #5: Higher effective tire pressure as you ascend

Guess 1 is wrong - our gasoline is generally 10-15% ethanol.


Guess 2, 3, & 5 are probably the reason with guess 2 being the seriously important one. P&G can boost fuel economy by up to 80% when done properly.

Guess 4 is correct for NA engines. The 1.4T engine in the Cruze LT, ECO, and LTZ uses the turbo-charger to keep the air/fuel mixture at the optimum for clean burn.

 

[obermd]

I also have dropped back to 40 PSI from 51. I like the ride better. I have seen a very slight drop in MPG but that could also be attributed to new tires.