whitenow

For those who still have & use AC: I find that mine is eating over 10% (2.7+) mpg.

This was determined by using the not-so-accurate, but assumed consistant onboard computer on avg mpg, driving the same paths at the same speed right after each other, and averaging 3 runs each of AC on & AC off.

I have been concerned that I average in the low 20's on the highway using onboard or manual calculation. For the first time in a long while, it was almost cool outside so I had rolled down the windows and turned off the AC. The onboard instant mpg was indicating around 28 mpg with cruise on at 70 mph. It had been in the low 20's with the AC on. The avg mpg indications are usually not as dramatic as the instant.

I turned on the AC and rolled up the windows, instant mpg's dropped to low 20's. AC back off, mpg's shot back up.

The next day I tried my experiment, gathered data and did calculations.

So, is my AC suspect according to what others are getting? AC is almost a requirement around here in Hell's Furnace.

cv67

I have never seen this discussed, all I know is i if its hot that AC is on even if it got 5 mpg.

GREGGPENN

I've always heard that A/C provides more efficient mpg than driving with the windows rolled down. IIRC, that's more-so on the hwy.

When driving 35mph or less, A/C's "advantage" starts to drop.

Never saw what vehicle(s) this test was performed on. I'll assume they were less aero-dynamic but with new bearnings/parts.

Turning on A/C does create a noticeable drop in power.

whitenow

That got me thinking, so I tried my experiment.

The avg mpg was not as dramatic, though, but still fuel for thought. Over 10%?

I'd just like some comparison before I race off for an expensive AC overhaul. Still recovering from Opti/water pump and back surgery from an unrelated issue.

npbassman

Interesting thread. I have a dedicated DD so I haven't calculated my mileage for AC vs no AC in the C4 but now I'm curious and need see what she reads this weekend. Gratuitous pic of daily driver mileage below!

radar502

My 96 LT-4 was running funny with the A/C on . And a little hot . Had it checked out at a very good A/c place ,come to find out the compressor was weak, new compressor runs like a new one..The A/C can make lot of stuff just not right ,most don't think abouit the A/C getting weak makeing thing off a little....

Flame Red

at least 5 MPG on all the cars/trucks I currently own. Of course it depends on the outside temp. Around here it is 95 6 months out of the year.

PLRX

In my Vette about 2 MPG

In my house the September electric (AC) bill is $285.

RollaMo-LT4

Forget even trying to do any tests or comparisons using the "Instant" mpg reading.
It means next to nothing, because in the next instant one of the parameters will change.
There is no way to have exact back to back tests under the same conditions unless your in a lab environment.

The only real way to do fuel mileage comparisons is to calculate out how much fuel your really using over a few tanks of fuel.
Any test using just a gallon or two will be meaningless.




Over the course of a full tank of fuel, you might save half a gallon not using the A/C.
On the highway, the extra wind resistance created with your windows down, almost offsets the power needed to run the A/C.

Red Dwarf

You can say that again!

RLG

In my house it was $440.00 for July.

RLG

How many dog power do you have?

PLRX

nutz4c4

Exacactly..... Don't care... cold air is good...

LT4BUD

With the windows up on the interstate......30mpg no air and 28mpg with air...

Saw more or less this same results on several road trips when car was near stock LT4

Fewer road trips with modded engine but now it is about 25mpg no air & 24 with air

So I would say about 1-2 mpg to run AC

Benny42

It takes about 2 HP per ton of capacity on r-12 & r134a. Your compressor is about 5 tons,
so it impacts fuel economy. Worth every bit of it here. ( rough calculations, YMMV)

GREGGPENN

Actually, despite my higher compression, higher heat-generating 383, I may use less than most of you guys. That's because I did the interior (heat barrier) insulation thing with the new interior swap.

I'll be honest, after I installed the 383, I thought "Oh shtt, this thing is going to be uncomfortable in the cabin. I may have to sell it." Of course, that was during the 1st 1000 miles of hotter-than-heck engine break-in time. Luckily, it was heading into fall/winter.

This spring, I applied the foil-backed insulation material sold at Home Depot. (In the front, I also used an 1/8" layer of asphalt squares on the floor pan.) I went up the transmission tunnel with the foil-backed stuff. And, insulated around the shifter.

Big difference. Huge difference. This summer, I didn't need to turn on the A/C until temps got well up into the high 90's. And, that's with an acrylic top. As long as I parked in the shade too. Seems more fun to hear the wind and sidepipes.

leesvet

yep...

I just paid a lite bill that they delivered on a handtruck...

In the car it cost me about 2-3 mpg avg...but worth it on the beautiful gulf of mexican coastline where the air is wet and warm....

The good news....my a/c cycled off this past week for the first time since May.

The repair guy that I called says they're supposed to do that when you;re not trying to air condition Hell.

leesvet

You;re in Magnolia?

wow, good luck. I know that a/c and mpg are the least of your worries this week. My brother lives in Indigo...

Good Luck !

Benny42

Thanks. We're about 8 miles from the fire line & the wind is favorable to
us. Good wishes to your brother.