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Old 07-06-2008, 02:30 AM   #1 (permalink)
Gas guzzler
 
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Big-Donkey Engine - '02 Chevy Tahoe
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20 MPG in Chevy Tahoe, Why?

Traveling 400 miles in Texas with one thing in mind. Economy. I was driving the family car, a '02 Tahoe (14/17mpg with a Vortec V-8) and gained a mere 3 mpg. I kept the speed low, sped up on downhills, coasted up hills, and pulsed to an extent. I kept the A/C off (to the great chagrin of my mother) and all vehicle conditions were ideal, although stock.

In 98 deg. Texas weather, is it advisable to block the grille? I understand AC won't work well, but hey, $4.00/gal? Crazy becomes wise at that point.

What did I do wrong? Why only 3 extra MPG? Should I have P&G'd more? With the auto tranny in the Tahoe, it decelerated rapidly with no gas, and popping it into N every 8 seconds for 6 hours seems a very bad idea. Advice?

Thank you for the 3 mpg, but I want more!

Logan W.

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Old 07-06-2008, 02:39 AM   #2 (permalink)
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3 MPG is a big difference on a low MPG vehicle. You saved around 15$ on that trip by my calculations.
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Old 07-06-2008, 11:20 AM   #3 (permalink)
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That's still almost a 20% improvement.

One of the problems with something like the Tahoe is aerodynamics and weight. To overcome rolling resistance and aero at 70-75mph, you probably need 40-50hp just to cruise!

Best thing on a heavier and less aerodynamic vehicle is to keep speeds low...

As an example, 85mph in my Aristo (similar to GS300) is just about the same horsepower as 65mph in my wifes Mazda Tribute. Vehicles weigh similar, but aerodynamics are vastly different.
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Old 07-06-2008, 12:25 PM   #4 (permalink)
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Check out the bottom graph I made up in this thread. I'd lower results a little for the extra size of the Tahoe perhaps, but may give you an idea of where to be.

http://ecomodder.com/forum/showthrea...html#post41430
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Old 07-06-2008, 03:27 PM   #5 (permalink)
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Wicked Wanda - '99 VW Beetle GLS
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My question is was the $15 worth the aggravation? I use hypermiling techniques when alone but I'd never submit my family to 6 hours in 98 degree Texas heat without A/C. If that money was the difference between going or not going then the shared sacrifice is understandable. If that had been my mom she would have said: "Here's a $20, put on the F&*%#g A/C!
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Old 07-06-2008, 03:37 PM   #6 (permalink)
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For me I'd say on a trip no its not worth it, but daily driven it does add up
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Old 07-06-2008, 04:12 PM   #7 (permalink)
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Mi-chan - '05 Toyota Corolla S
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you have to look at the % improvement, not just the numbers. 3 mpg is a lot for 14/17..
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Old 07-06-2008, 05:29 PM   #8 (permalink)
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On a road trip, in a large vehicle with a huge Cd, your best bet is to inflate the tires somewhere between factory spec and sidewall max, use the a/c on recirculate, and drive at the speed limit, tailing a truck by 5+ car lengths for safety.

P&G is not advisable for an automatic transmission, plus you have to use the starter to restart the engine, which uses lots of electrical energy that must be made up by the alternator. In a manual, you can bump start and eliminate damage and electrical losses
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Old 07-07-2008, 02:04 PM   #9 (permalink)
Gas guzzler
 
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Big-Donkey Engine - '02 Chevy Tahoe
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The ac was broke

Therefore, we could only use it below 70mph and only on low uphill grades. Compressor is going out.
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Old 07-07-2008, 02:29 PM   #10 (permalink)
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I think there was another thread complaining that MPG is a poor measure because 3mpg gain at 17 is twice as big as a 3mpg gain at 34. But just think, that means your next 3 should be cake

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