Quote:
Originally Posted by MeteorGray
I drive my Mazda3 mostly on long commute trips on the highway, and as already noted, I can't tell the difference in fuel mileage with and without the air conditioner. I try to see evidence of it on the Scangauge via its instantaneous mileage readout, but the variations of highway, wind, etc tend to mask any contrast between "on" and "off" mileage differences for me. I know the air conditioner takes energy to run, but it's small enough that I can't "see" it, either on the Scangauge or at the fuel pump.
One technique I use when I don't have a passenger is to push the button that controls the air conditioner's compressor on/off activation. I leave the thermostat/temperature setting on "maximum cold," and when I get cold, I push the button to turn off the compressor and let the temperature gradually rise until I'm too hot, then repeat the cycle. When I push the compressor button, I can't tell any difference except for the temperature of the air; ie, I can't "see" whether the compressor is on-or-off on the Scangauge or "feel" it via the ambience of the car or in any other way to indicate the compressor is running.
One reason I use the compressor's on/off button in this way is the fact that at one time in automotive history (and maybe today in some cars?), some genius figured it was a good idea to let the compressor run all the time and use the engine's hot water to moderate the cabin temperature. It works, but at a higher fuel price. A workaround for me was the compressor on/off technique. I don't know if it's better for fuel economy on my Mazda or not, since I suspect the Mazda's compressor cycles as needed and doesn't use the "hot water" idea. But, is it better for FE to use the on/off technique or just set the temperature/thermostat at the desired temperature level and let the compressor cycle? Don't know.
In any case, I'm too old to drive around in a tropical climate while being hot and sweaty with the roar of hot-and-humid-and-dirty air blasting through the car for several hundred miles at a stint. I just can't take that anymore. Nosir.
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It’s not temp modification so much as it is humidity control. It’s also an extra level of dust removal. Start with air on Recirc, move to Norm, and then to Bi-level. Crack a rear window slightly until that last change.
Control over humidity while parked is a goal for you. Given shade (no direct sun) the A/C load is then minimized.
Plenty of legal window tint the other. 3M makes a huge variety ($ to $$$$) and it’s likely you’ll need to head to Houston or Dallas for the right installer for the good stuff. Quality matters. (I use REFLECTIX press-fit interior shades cut from the four foot tall rolls for my pickup & big truck. Use the windshield one EVERY time you park while on errands).
Inspect the door & window seals. R & R as needed.
And, yes, a sheepskin seat cover (medical grade) helps.
Every vehicle takes 1.5-hrs to warm-up (tire pressure equalization). 45-miles just to get oil to operating temp. Coolant temp means little.
Its burning off the accumulated crankcase acids that counts, thus trips under three hours are to be avoided.
As a member of EM it (should) be fair to assume you’ve eliminated the multiple short trips you may have once made as a matter of course.
Thus long trips are highlighted for
highest average mph as a greater percentage of use.
HVAC use is BEST for highway as airborne pollutants are reduced. Fatigue via wind noise is reduced.
HVAC is thus a
fuel savings as the INEVITABLE onset of operator fatigue recedes farther into the day.
The “penalty” for A/C use correlates with full warm-up and overcoming short trip acids, etc. At three-hours plus, it’s using more than would the heater (per se), but today’s cars aren’t built with dash-controlled kickpanel vents and front vent windows. There’s no “Intermediate” adjustment of exterior-admitted airflow without the HVAC system. (No spring or fall, as one guy said).
As I my post above, what’s the actual ANNUAL CPM penalty? 3/100’s of a cent? A half-cent? Two cents?
Solve for that number.
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