Wow, A/C sucks!
 

But with 90+ degree F summer temps, I need it. I have noticed my FE has dropped a good 5-6 mpg over the last 2 tanks because of it (and because I had to sit a few times with the ICE on to keep it running so my 7 mo old nephew could stay cool).

Is it normal for other cars to see such a dramatic drop in FE with the A/C? Just when I got proud of myself for getting a 28 mpg hwy '96 VW Golf up to 38-39 mpg per tank by coasting with the ICE on, my last two tanks dropped back down to 33-34 mpg. I've lost almost 16% over the last month!

Yes, engine driven A/C reduces FE somewhat - in the case of my VX about 10%. I'll trade 5 mpg for cool comfort any time.:D

Must have been difficult for our grandfolks years back to survive who never had an AC to turn on. ;)

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I don't have a/c at work. I survive. On days I work I generally don't turn the a/c on in the truck as I will just get upset and miserable to get nice and cool, and then get out and not be in a/c. I use it all the time when I'm not working though.

I recall an advertisement I saw when I was a little kid from about 1930 for Dodge Brothers. The picture told a story which made me wonder what was on the ad guy's mind. A black car. Summer vacation traveling through Hopi or Navajo country, Arizona or New Mexico. Father sitting inside behind the wheel, a look of sweltering dejection on his face. Mother is outside the car, talking to an Indian lady. Little girl is outside the car, talking to an Indian girl, both holding their dolls. The picture is composed so your eyes are drawn to the man behind the wheel. You could almost feel the sweat soaking through his shirt into the upholstery!

Ah, if your passengers ***** a lot about the temps, all you have to do is set the cabin to recirculate, turn on the ac on max blast with fans max speed for about 30secs to a minute and then turn off the AC with the fans set to a slow speed. You save no gas by taking advantage of climate control because all it does is keep the AC running continuously oppose to short bursts. Not to mention running a lower setting doesn't actually reduce the load of the compressor by one bit, it just dilutes it with the hotter outside air.

1st choice run AC when you are DFCOing, it's basically free.

Always on recirculate, you only need to remove the humidity once, and you are recooling the same air.

2nd choice run AC in your pulse since you are near peak of BSFC map already the power is cheap, relatively speaking.

3rd get it cool then go to low fan speed recirc, cycle the compressor manually for a pulse and glide ac, with about a 20 degree temp spread. Use higher fan speed if necessary.

All this being said AC really kills my mileage in my VX, at least 10 %, possibly as high as 15%.

One way I get ahead of the curve is to turn it on when engine is cold and car has been sitting in the garage with lower temps than ambient. Park in the shade if you can so you have less heat to get rid of. Drive with windlows open when it really is steaming inside.

I probably havent used mine for 250 miles in the last 4000. Mileage dropped by more than 10 MPG when I did and that was only when ambient temps went above 90, or we were dressed up and didn't want to get there sweaty.


regards
gary

With the Cadillac, using the AC causes the mileage to drop by maybe 1-2 mpg. Of course, that works out to 5-10%. Someone removed the Geo's AC compressor before I ever got the car, and the condenser was pretty much toast. I'm not that worried about replacing the AC in the Geo, but I believe the condenser sprang a leak on the Cad, have to take care of that sometime soon.

Sounds like your caddy is running pretty good for a 4100 engine. I was looking at buying an 84 Fleetwood Brougham when my Buick was rear ended years ago, but it had the 4100 with 80,000 miles on it. I passed.

The problem with the 4100, besides the fact that it was barely enough engine to make a Fleetwood move (The Fleetwoods with the 5.7 ((350)) were much more fuel efficient because the engine didn't have to labor to move that large car. The 4100 head gaskets were made out of something that was not commonly used in vehicle gaskets. I don't remember what it is now. What was supposed to happen was whenever you changed the coolant you were supposed to add an additive to the coolant, only available at a Cadillac dealer. The additive did something to the coolant so it didn't eat away at the head gasket. Most owners didn't know about this so the additive was not used in most of the cars. Most often the head gaskets would go between 90,000 and 120,000 miles. This is why I didn't buy that 84 Fleetwood. It had 80,000 miles on it and I had no way of knowing if the maintenance was properly done. The Cadillac dealer wanted $5,000 or $6,000 for it, and I felt that was too much to pay for a car that I may have to tear down and rebuild within the next year or two.

Depends on the car. As described in another thread by someone else, his DFCO is effectively canceled and useless when A/C is on. He had to DFCO above 2000rpm with A/C vs. something like 850rpm cutoff without A/C.

That engine was prone to more problems than just that. Had it in my '87 Deville. I loved that car but I was a kid with money, no patience for a broken car, and a need for speed so I bought a new car. Now I wish I had kept it and hadn't done some of the ugly hacks that I did...I could do so much with it now.