What kind of Air Conditioning ON Mileage are you getting on your 85 300D? - PeachParts Mercedes-Benz Forum

Carrameow · #1 06-19-2006, 01:51 PM

What kind of Air Conditioning ON Mileage are you getting on your 85 300D?

1. To my horror, I got 300 miles from 16 gallons last week with my AC on!

2. Without AC I'm getting 370 miles from 16 gallons or better!

Does anyone else feel this way? I haven't timed my IP or changed my chain yet (Engine has 250K on it) but I was surprised at this mileage!

Anyone got any Mileage enhancing Hints?

Carrameow · #2 06-19-2006, 02:04 PM

I just remembered she wasn't kicking out at High Speed. The Turbo boost signal is probably not getting thru and the turbo is not doing its thing and the AC may have nothing to do with it.

Gary F. · #3 06-19-2006, 02:08 PM

On mine, which by the way I just figured running WVO, 24.8 with AC on.

coldwar · #4 06-19-2006, 02:27 PM

Myth Busters covered this last week. By putting measured amounts of gas in two identicle Ford SUV's, they got considerably more mileage out of driving with the AC off and windows down. But using a computer method monitoring engine airflow, they showed it's better to have the windows up and AC on. They felt the computer method was flawed, because it only would work "under ideal conditions"- which to me was a stupid conclusion because they were not comparing two vehicles with the computer- only one- first with AC, and second with windows down, under identical conditions, same vehicle, with computer giving a real-time MPG readout (which was only 11 MPG at 55 MPH btw., proving that SUV's are PIGS no matter what)

Dave

Panzermann · #5 06-19-2006, 06:34 PM

Quote:

Originally Posted by coldwar

Myth Busters covered this last week. By putting measured amounts of gas in two identicle Ford SUV's, they got considerably more mileage out of driving with the AC off and windows down. But using a computer method monitoring engine airflow, they showed it's better to have the windows up and AC on. They felt the computer method was flawed, because it only would work "under ideal conditions"- which to me was a stupid conclusion because they were not comparing two vehicles with the computer- only one- first with AC, and second with windows down, under identical conditions, same vehicle, with computer giving a real-time MPG readout (which was only 11 MPG at 55 MPH btw., proving that SUV's are PIGS no matter what)

Dave

I seem to recall that the results indicated that the window open was effecient until about 40 mph, then the turbulence created by the open windows increased drag beyong that point where it was better to have them closed and use the fan or a/c. You can have the fan alone on to provide ventilation, and the a/c compressor won't be using any power. Of course, in AZ, you've got to use the a/c (at least I do).

Hatterasguy · #6 06-19-2006, 06:38 PM

SDL's mileage isn't so great around town, last tank was old fuel but only 21.5. I'll be interested to see what she does on fresh fuel. My driving has been 95% around town lately with the AC on about half the time. Although in past years I have only noticed a very slight drop with AC usage, 1mpg at most.

The car is in perfect tune, short of putting in a new crate engine I don't see what else I can do to improve that.

engatwork · #7 06-19-2006, 09:17 PM

I don't care what kind of mileage I get when the a/c is blowing cold - as long as it is blowing cold

. I have never really paid that much attention to it.

MeinGreaseCar · #8 06-19-2006, 09:41 PM

AC isn't working yet.

But I just went 510 miles on a tank of b100, and the reserve light wasn't on yet.

Jadavis · #9 06-19-2006, 10:15 PM

I know it is a different car and different engine, but I got 23 mpg on the highway doing 75-80 through rolling hills. I'm not happy with it, but I'm still working through some issues. (I have not added the injector heaters yet and it is running on 50% D2, 25% biodiesel, 25% WVO. It does have a flat plate heat exchanger.) On D2 it gets 26 MPG. Even that is a bit low.

Didn't these things get more like 29 at those speeds? 35 at 55-60 MPG.

(New air filter, new primary and secondary fuel filters, just had the oil changed, tires were just rotated and balanced, alda needs to be adjusted but is hard to get at, transmission fluid and filter changed to synthetic 2-3000 miles ago, new plugs...oh, wait...um, scratch that.)

Jim

Hatterasguy · #10 06-19-2006, 10:47 PM

Jim check IP timing, also check chain stretch. Also if your injectors have not been touched its time.

Their is a lot you can do to freshen up these engines. But is it really worth spending a few thousand dollars to gain 1-2mpg? As in the case of Brain's 300SD...

Panzermann · #11 07-23-2006, 07:37 PM

...on the road from Tucson to San Diego in 110 degree F heat in my 83 300TD. Going 75-80 mph. A/C on full. Car uncomfortably cold. Only turned it off for two grades that I had to go up. Major recent changes in the car are placement of rebuilt injectors, which increased mpg from the 19-21 range under similar circumstances. I must say that I was impressed. Take home message: major determinant of fuel efficiency will be the quality of basic engine maintenance.