How many tanks of gas?

[JB.]

Question: Does the AC really effect mpg's? To the point where you notice a differece in mpgs's driving when ac off vs on?

Yes, but a lot of factors come into play including behavioral. For instance, where I live (and you too, looks like) idling the truck in the winter for heat doesn't come up very often and when it does, between mild temps and solar radiation, it doesn't take much to keep the truck warm. In the summer, it's a different story. So, not only more idling in the summer, but the percentage difference in engine work when idling with compressor on/off is much larger than the net effect when freeway driving. So gas burned via idling goes up considerably. Also, if you're in tune with the way the truck accelerates and want to maintain that feel throughout the summer against the drag of the compressor, that too consumes comparatively more gas than compressor coming on at 75mph. Would be interesting to see the math on that one. DC runner?

Additionally, in my case, the reduced summer mpg causes me to ignore mileage and just enjoy the way the truck drives. Come winter, when the compressor won't be running much, I pay attention to mileage. Net result for me, around 3 mpg difference between summer and winter, but even without this effect, I would expect it to be around 1.

 

[Bigmikelakers]

I have an 04 Accord 4 banger and I drive with the AC on about 99% of the time. Can't stand driving with the window down. I should experiment if I get better mileage with it off.

 

[JimKW]

I have also watched how speed affects my mileage also. In my Volvos I find that 70 mph is a magic number. Between 55 and a little less that 70 my mileage is close to the same. When I hit 70 and over the mileage goes down and the faster I go the worse my mileage is. I think the optimum speed for the Volvos is 60-65, and on a trip I usually stay right around 68 when I don't care how long it takes to get there.

 

[tacticalcustoms]

google gave a traveling distance of 1 day 11 hours
2,183.2 mi - I-40 W

I can easily achieve 18mpg highway and I usually put in about 18 gallons.

If I lived in Kentucky I would get to LA in 7 fill ups so around 500.00 to drive one way

 

[tacticalcustoms]

I have an 04 Accord 4 banger and I drive with the AC on about 99% of the time. Can't stand driving with the window down. I should experiment if I get better mileage with it off.

you'll get better gas mileage while its off and the windows are up. but once those windows come down, gas mileage will decrease.

 

[Carl_G]

I was joking, relax.

Ok, so add one more step. Total Gallons/Tank size= fill ups.

COME ON. My joke was this math is very, very simple. 23 Gallon tank, assume you actually use 18-20 each fill up. It isn't hard.

Don't get your feathers ruffled.

Not ruffled don't worry but I do notice your posts (227 since August first) follow an interesting pattern and remind me of someone who used to post here: he loved the V8 and was quick to debate regardless of topic 

Oh and your post about drag racing a v6 4th gen. and hearing something blow up as you shot past him? Incredible to say the least.

 

[-06T4R-]

Technically, yes. Informally, No. Modern AC units are far more effiecent than older days.

I know I am the math nerd on here, but the single BIGGEST factor in MPG is speed. Power dissipated by a car is equal to the cube of the velocity. So a doubling in speed requires 8 times the power, which is why most cars can do 100 without too much trouble, but hitting 200 requires a real beast of a machine.

What I am saying is, the difference in energy required to move 40 MPH and 80MPH is higher by 8 times. 8 TIMES!

We can debate the measly 1% a modern AC takes from your car, or we can focus on the real culprit. To put it in easy estimation, every 10mph increase in speed between 40mph and 80mph requires twice the power needed before it.

TWICE the total power. We are talking orders of magnitude here on power. So, you will see a greater fuel savings by slowing down 5 mph than you would with almost every other factor combined. Type of gas, air in tires, AC or NO ac. Windows or NO windows. Weight and load...

This isn't even something subject to discussion. We have know aerodynamic principles for years and know that traveling higher than 55 mph starts a huge power drain curve that eats energy.

I am not saying DON'T go faster, I am saying; if you really want to save gas, or you really want to increase MPG... slow down.

Agreed.

I just finished a trip to the beach (round trip was about 375 miles) in my 06. 6cyl SR5. I made sure I drove 65 the entire time and ended up with a 1/4 of a tank after the trip.... Average was around 23mpg's (by hand not digital readout).

That same trip going 75-80 uses about a half a tank more.

I was pretty impressed, but driving conditions were optimal.

 

[MikeInNH]

you'll get better gas mileage while its off and the windows are up. but once those windows come down, gas mileage will decrease.

Can't make a general statement like that. Each vehicle is different. The more aerodynamically a vehicle is designed the more likely opened windows will have an effect on it's performance and mpg. Some vehicles will actually see a decrease in gas mileage when the AC is on and the windows are up as opposed to Windows closed and AC is on. Others will be the opposite.