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Old 02-06-2010, 10:40 AM   #5 (permalink)
rmay635703
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Join Date: Jun 2008
Location: Somewhere in WI
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Silver - '10 Chevy Cobalt XFE
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Quote:
Originally Posted by ahanix1989 View Post
Hey everyone, this is gonna be a fun project.
Right now, during winter, I average 11.8mpg. During summer, I get closer to 15. "Driving variances" doesn't really apply, it's ALWAYS 11.75 to 11.83 mpg, no matter how I drive.

But you guys are the experts on this. What would you all recommend?
You can do better than 11.75mpg with a stock 5.2 even in town but you need to rework your route usually. You also need an engine heater if your trip is shorter than 10 miles or you simply can't get the things to do better without extreme measures driving wise. I would estimate that this motor even with many aero mods would see little benefit in the winter on short trips without a magnetic or gel blanket heater on the bottom to keep things warm

Also how much air pressure do you have in the tires? I can get about 2-4mpg better with 60psi (depending on how far I am allowed to coast and what speed)

Your vehicle has a lot of inertia even one stop and go reduces fuel economy even on short trips by about 1-3mpg as measured by my scanguage. Think about the number of times you stop and from what speed. Think of the # of times you have to use brakes. The potential fuel economy on this vehicle is only around 18mpg-20mpg steady state & better P&G, even in the winter but you can't actually reach that except if you have a long trip with no stops.

The main issue I have with my trip is that I can't coast far enough on my trip into work and around oshkosh. To get 20mpg you need to be able to coast down fully at every stop. If you ARE NOT COASTING DOWN TO 8 MPH you are not getting your full FE potential and stopping straight from anything above 20mph kills fuel economy massive (I am talking experience)

If your vehicle is OBDII beg/borrow a scanguage if you can afford it. You will see there is a lot to be gained on a 5.2 from driving technique alone, especially at lower speeds.

One last thing, if you coast to a stop always coast in neutral never in drive, dodge has the motor set to burn more fuel in gear; sometimes on the highway almost double in gear compared to neutral.

Lastly this post was not to discourage you, I am just stating facts about your vehicle, aero is only going to be the most effective if you can get the motor warm and only if you are driving about 40/45mph much of the time. Grab the low hanging fruit first. If you have a lot of stops you need to be able to coast down as much as possible regardless of your aero situation. And lastly 5.2's don't like being babied when you accellerate, either accelerate or drive a steady speed but nothing in between when you are in gears below 3rd. Generally firm acceleration but not to the floor accelleration. And don't diss wavering the accelerator pedal before taking off from a stop, its worked now in 3 dodge vehicles, must be some strangeness with the computer and slushbox.

Good Luck
Ryan
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