Winter kills fuel mileage
02-17-2014, 02:44 PM
#41
AudiWorld Super User
I've lived in places where it was -20F in the morning, and watched my oil pressure gauge slowly climb once the car begrudgingly started. Of course the Alyeska Pipeline workers routinely had to work at -60F where top quality stainless tools snapped like sugar candy. But that was old news in Siberia, where Russian construction workers would call -60F a really good day.
Cold? There's limit to what rotates on a car, and again, the rotating parts heat stabilize fairly quickly when in use, unless you're talking about poking down a mountain road in double low. Even then, there's a limit to thermal effects and moving parts.
Krytox: Great stuff, I've used it for over 20 years. The typical temperature range is -70F to +700F but it is not available in really low viscosity formulations, at all. Neither the Krytox greases nor the oils really compare to other "thin" lubricants. Krytox's major selling point is that the damn stuff is INERT. Doesn't oxidize, doesn't react to chlorine, sulfur, petrochemicals, UV. Doesn't migrate. Doesn't conduct. Great stuff for many reasons--but not the right lube for all purposes. Last time I bought wheel bearing grease, coincidentally from Dow Corning's industrial division, their 'top' product was the radically new molybdium disulphide grease for that purpose. Today they also sell Krytox with moly additive, but I haven't heard them pushing that for wheel bearings.
The rest of the car? Best to keep the Krytox on the ignition wiring.<G>
Cold? There's limit to what rotates on a car, and again, the rotating parts heat stabilize fairly quickly when in use, unless you're talking about poking down a mountain road in double low. Even then, there's a limit to thermal effects and moving parts.
Krytox: Great stuff, I've used it for over 20 years. The typical temperature range is -70F to +700F but it is not available in really low viscosity formulations, at all. Neither the Krytox greases nor the oils really compare to other "thin" lubricants. Krytox's major selling point is that the damn stuff is INERT. Doesn't oxidize, doesn't react to chlorine, sulfur, petrochemicals, UV. Doesn't migrate. Doesn't conduct. Great stuff for many reasons--but not the right lube for all purposes. Last time I bought wheel bearing grease, coincidentally from Dow Corning's industrial division, their 'top' product was the radically new molybdium disulphide grease for that purpose. Today they also sell Krytox with moly additive, but I haven't heard them pushing that for wheel bearings.
The rest of the car? Best to keep the Krytox on the ignition wiring.<G>
02-18-2014, 08:20 AM
#43
AudiWorld Super User
"FYI, defrosters uses the AC compressor which tend to use more gas to run it"
That would be an Audi engineering failure then. Others just use the heat, since heating the air also dries it, and defrosts perfectly adequately. If you use the compressor, you've produced cold air, which then has to be heated even more in order to defrost or de-ice a windshield.
Many, if not most of us, run the compressor all summer long anyhow, so using it to a much lesser extent in the winter shouldn't "decrease" comparative mpg in any case.
That would be an Audi engineering failure then. Others just use the heat, since heating the air also dries it, and defrosts perfectly adequately. If you use the compressor, you've produced cold air, which then has to be heated even more in order to defrost or de-ice a windshield.
Many, if not most of us, run the compressor all summer long anyhow, so using it to a much lesser extent in the winter shouldn't "decrease" comparative mpg in any case.
02-18-2014, 11:30 AM
#44
"FYI, defrosters uses the AC compressor which tend to use more gas to run it"
That would be an Audi engineering failure then. Others just use the heat, since heating the air also dries it, and defrosts perfectly adequately. If you use the compressor, you've produced cold air, which then has to be heated even more in order to defrost or de-ice a windshield.
Many, if not most of us, run the compressor all summer long anyhow, so using it to a much lesser extent in the winter shouldn't "decrease" comparative mpg in any case.
That would be an Audi engineering failure then. Others just use the heat, since heating the air also dries it, and defrosts perfectly adequately. If you use the compressor, you've produced cold air, which then has to be heated even more in order to defrost or de-ice a windshield.
Many, if not most of us, run the compressor all summer long anyhow, so using it to a much lesser extent in the winter shouldn't "decrease" comparative mpg in any case.
02-18-2014, 11:44 AM
#45
AudiWorld Super User
I'll set up a road block tonight, and ask all drivers to turn on front defrosters for testing. 
Seriously? I can tell you for certain that on my last car, the AC compressor absolutely did not engage when the defroster was used. The compressor was manually selected by the AC button, but the choice of defroster outlets and air temperature was by two manual slide controls, and they couldn't engage the compressor without the assistance of my finger.
Maybe the fancy luxury cars (VW says Audi is a luxury car) with integrated "climate control" systems are using the compressor these days, but a normal heating and AC system does not always do that.
And again, these days? Using the compressor is normal, even in the summer it is supposed to cause less load on the engine than the wind drag from opening your windows. Using the compressor and the AC in June, to establish a baseline of "normal" mpg, you'll still be using less compressor than the front defroster uses, so I still have to say that's no excuse for lower mpg in the winter.
And I don't recall anyone mentioning how much "lower" lower is. AFAIK they're only seeing the 10% drop from E-10.
You know, when you hear hoofbeats, and you're surrounded by horses, don't look for zebras.
Seriously? I can tell you for certain that on my last car, the AC compressor absolutely did not engage when the defroster was used. The compressor was manually selected by the AC button, but the choice of defroster outlets and air temperature was by two manual slide controls, and they couldn't engage the compressor without the assistance of my finger.
Maybe the fancy luxury cars (VW says Audi is a luxury car) with integrated "climate control" systems are using the compressor these days, but a normal heating and AC system does not always do that.
And again, these days? Using the compressor is normal, even in the summer it is supposed to cause less load on the engine than the wind drag from opening your windows. Using the compressor and the AC in June, to establish a baseline of "normal" mpg, you'll still be using less compressor than the front defroster uses, so I still have to say that's no excuse for lower mpg in the winter.
And I don't recall anyone mentioning how much "lower" lower is. AFAIK they're only seeing the 10% drop from E-10.
You know, when you hear hoofbeats, and you're surrounded by horses, don't look for zebras.
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