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Low pressure tires
Volkswagen Golf, Jetta, Corrado, Vanagon, new models, etc. (rec.autos.makers.vw.watercooled)
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#21
 
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Re: Low pressure tires -
10-26-2006
, 06:20 PM
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Affects gas mileage in all vehicles, regardless of vehicle or engine size. Ever see the Mythbusters TV program? They used 2 identical Ford SUVs. One using AC, one not. No difference in mileage they said. "Myth" busted they said. I still don't believe their results. Yeah, I saw it last night, in fact. Couple of doofuses with no scientific backgrounds. If they found no difference in mileage, then their measuring methods were inaccurate. You can't create energy for free, if the AC uses power, it decreases gas mileage. And AC does use power. They can't bust the "myth" of cold, hard physical reality. How drastically can tire pressure affect gas mileage in similar older VW with small engine (1.8L)? A couple of percent. Kinda depends on the vehicle and the power to weight ratio in my opinion. That's why it's expressed in a percentage, and not an absolute number. Besides, you specified an older VW with a 1.8 engine, didn't you? |
on the door pillar or gas fill lid on the last 3 water cooled VWs I
owned. I guess it was in the owners manual for the air cooled VWs but
I cannot recall. I do not have any air cooled VWs to look at either.
1.8L engine. Well some folks could have a 1.8L in a 1952 VW if they
did some hot rodding. Older is not a very definitive term. Kind of
like a tank of fuel. My car manual says it holds 14.5 gallons US but I
often pump 16 gallons in. Capacity should not be vague. It sure was
not in the mid sixties VW fuel tanks.
#22
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Affects gas mileage in all vehicles, regardless of vehicle or engine size. Ever see the Mythbusters TV program? They used 2 identical Ford SUVs. One using AC, one not. No difference in mileage they said. "Myth" busted they said. I still don't believe their results. Yeah, I saw it last night, in fact. Couple of doofuses with no scientific backgrounds. If they found no difference in mileage, then their measuring methods were inaccurate. You can't create energy for free, if the AC uses power, it decreases gas mileage. And AC does use power. They can't bust the "myth" of cold, hard physical reality. |
particular hypothesis. They used Full-size SUVs with big V8 engines, and they
did the test at IIRC 45mph because of the sharp corners on the test track they
used. Silly really. The idea was to see if driving with the windows open used
more gas than running the A/C. On a big SUV at 45 mph, it was a wash. On a
properly aerodynamic car at a realistic highway speed, it would not be. Modern
A/C compressors are extremely efficient, while driving with the windows open
at 75 mph royally screws up the aerodynamics. And of course, as speed
increases, the relative percentage of the engines power needed to run the A/C
compressor decreases. Takes the same amount of power to run the compressor at
idle as it does at highways speed.
Kevin Rhodes
Westbrook, Maine
#23
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In article <bI40h.3424$T_1.632 (AT) newssvr14 (DOT) news.prodigy.com>, Brian Running <brunning (AT) XXameritechXX (DOT) net> wrote: Affects gas mileage in all vehicles, regardless of vehicle or engine size. Ever see the Mythbusters TV program? They used 2 identical Ford SUVs. One using AC, one not. No difference in mileage they said. "Myth" busted they said. I still don't believe their results. Yeah, I saw it last night, in fact. Couple of doofuses with no scientific backgrounds. If they found no difference in mileage, then their measuring methods were inaccurate. You can't create energy for free, if the AC uses power, it decreases gas mileage. And AC does use power. They can't bust the "myth" of cold, hard physical reality. Mythbusters used just about the worst possible circumstances to test that particular hypothesis. They used Full-size SUVs with big V8 engines, and they did the test at IIRC 45mph because of the sharp corners on the test track they used. Silly really. The idea was to see if driving with the windows open used more gas than running the A/C. On a big SUV at 45 mph, it was a wash. On a properly aerodynamic car at a realistic highway speed, it would not be. Modern A/C compressors are extremely efficient, while driving with the windows open at 75 mph royally screws up the aerodynamics. And of course, as speed increases, the relative percentage of the engines power needed to run the A/C compressor decreases. Takes the same amount of power to run the compressor at idle as it does at highways speed. Kevin Rhodes Westbrook, Maine |
the spring and fall then it does in the summer. I have windows open
but not wide open in the spring and fall. AC in the heat of summer. No
myth busting there. I don't worry as much about crummy mileage in the
summer but if it is crummy in the fall and spring I am lookng for
reasons. My 84 GTI used to lose about 10% when running the AC. About
the same as the mileage loss on the Jetta as it could dip down to 45
mpg.
#24
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My 2003 Jetta diesel gets about 3-5 miles per gallon better mileage in the spring and fall then it does in the summer. I have windows open but not wide open in the spring and fall. AC in the heat of summer. No myth busting there. |
--
Mike Smith
#25
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Jim Behning wrote: My 2003 Jetta diesel gets about 3-5 miles per gallon better mileage in the spring and fall then it does in the summer. I have windows open but not wide open in the spring and fall. AC in the heat of summer. No myth busting there. Could seasonal fuel variations have anything to do with it? |
tank it will go back up with no AC. I could flip back and forth as the
weather does. Fuel mix does not flip but the temps do. We had a few
days of frost already and then 70+ days a few days later.
I do not know for sure how much the summer/winter diesel mix affects
mileage. I do know straight B100 chicken fat base causes about a 5% or
more drop in mileage but better smelling exhaust. I have not run soy
bio in a long time. I do not know how it affects mileage.
http://www.theoildrum.com/story/2006/9/13/234043/431
#26
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On Thu, 26 Oct 2006 23:12:29 GMT, krhodes (AT) nospam (DOT) maine.rr.com (Kevin Rhodes) wrote: In article <bI40h.3424$T_1.632 (AT) newssvr14 (DOT) news.prodigy.com>, Brian Running brunning (AT) XXameritechXX (DOT) net> wrote: Affects gas mileage in all vehicles, regardless of vehicle or engine size. Ever see the Mythbusters TV program? They used 2 identical Ford SUVs. One using AC, one not. No difference in mileage they said. "Myth" busted they said. I still don't believe their results. Yeah, I saw it last night, in fact. Couple of doofuses with no scientific backgrounds. If they found no difference in mileage, then their measuring methods were inaccurate. You can't create energy for free, if the AC uses power, it decreases gas mileage. And AC does use power. They can't bust the "myth" of cold, hard physical reality. Mythbusters used just about the worst possible circumstances to test that particular hypothesis. They used Full-size SUVs with big V8 engines, and they did the test at IIRC 45mph because of the sharp corners on the test track they used. Silly really. The idea was to see if driving with the windows open used more gas than running the A/C. On a big SUV at 45 mph, it was a wash. On a properly aerodynamic car at a realistic highway speed, it would not be. Modern A/C compressors are extremely efficient, while driving with the windows open at 75 mph royally screws up the aerodynamics. And of course, as speed increases, the relative percentage of the engines power needed to run the A/C compressor decreases. Takes the same amount of power to run the compressor at idle as it does at highways speed. Kevin Rhodes Westbrook, Maine My 2003 Jetta diesel gets about 3-5 miles per gallon better mileage in the spring and fall then it does in the summer. I have windows open but not wide open in the spring and fall. AC in the heat of summer. No myth busting there. I don't worry as much about crummy mileage in the summer but if it is crummy in the fall and spring I am lookng for reasons. My 84 GTI used to lose about 10% when running the AC. About the same as the mileage loss on the Jetta as it could dip down to 45 mpg. |
#27
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The idea was to see if driving with the windows open used more gas than running the A/C. |
uses much more fuel than any losses due to aerodynamics with the windows
open. No way that windows could possibly cause that much drag. That is
the conclusion that Road & Track reached in a recent test, too. As
someone else mentioned here in this thread, there's a clear-cut
correlation between using AC and loss of fuel mileage, but no
correlation between having the windows open and losing mileage. Does
anyone feel the car slow down or hear the engine start to pull a little
harder when they lower the windows? Of course not. But you do feel
that momentary bump when the AC compressor kicks in.
That one really is a myth. AC costs fuel, pure and simple.
#28
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The idea was to see if driving with the windows open used more gas than running the A/C. Oh, THAT myth! Okay. There's no doubt in my mind that running the AC uses much more fuel than any losses due to aerodynamics with the windows open. No way that windows could possibly cause that much drag. That is the conclusion that Road & Track reached in a recent test, too. As someone else mentioned here in this thread, there's a clear-cut correlation between using AC and loss of fuel mileage, but no correlation between having the windows open and losing mileage. Does anyone feel the car slow down or hear the engine start to pull a little harder when they lower the windows? Of course not. But you do feel that momentary bump when the AC compressor kicks in. That one really is a myth. AC costs fuel, pure and simple. |
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