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#1
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8-9 MPG loss with A/C on
I am seeing about 8 to 9 miles-per-gallon lost when I have the A/C on.
So, from about 29-30 down to 21 .... is this normal? This is my first summer driving the car, so I am not sure what to expect as in terms of what MPG to expect ... but 9 MPG seems kinda high? Is 33% loss average and to be expected? Its a '77 300D converted to 134a. A/C was just serviced last week. Thanks all, -graham |
#2
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134a does have higher pressures, resulting in the engine working harder to turn the compressor. But, not enough to reduce MPG that much.
Has your driving habits changed? Is the tranny slipping a bit? When was the last valve adjustment? 8-9 MPG less does not sound right. I think you have other issues. A dragging brake pad or E-brake will also make the engine work harder to maintain speed.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 99 W210 E300 TD Turbo, chipped. Still needs EGR Delete, 228K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#3
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Quote:
Well, it just got back from the mechanic from which I told him to repair/replace anything that was bad - so I would expect to hear something else about it, other than the work that was done. However, that is not to say that something was overlooked. No, I don't think my driving habits have changed. I drive approx 140 miles a day (mostly on the interstate) and I have been monitoring this with and without the AC on. These past few days I have been sweating it to confirm my diagnosis and it's back up to 29-30MPG without the AC. Now you got me thinking about my driving habits! I will drive the next few days with the AC on as normal as I can, and report back. Thanks! -graham |
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I am beginning to wonder if the ultra-low sulphur is impacting my mileage. I did some very smooth highway driving for 400 miles today and only got about 24.6 mpg. I did have the a/c essentially the entire time though.
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http://i284.photobucket.com/albums/l...aman/Fleet.jpg Peach Parts W124.128 User Group. 80 280SL 85 300SD 87 300TD 92 300D 2.5 Turbo 92 300TE 4Matic |
#5
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Ah yes, the "hand them a blank check" statement.
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#6
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I usually have them consult me before doing any major work w/o my knowing
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#7
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My mileage went down from an average of around 27.5 to around 24.5 once ULSD was the only fuel around here. I have been putting in Lucas additive to restore the lubricity and the mileage has gone back up to around 26. You only need a little additive to restore lubricity to the fuel. Give it a try...
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"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy" Current Monika '74 450 SL BrownHilda '79 280SL FoxyCleopatra '99 Chevy Suburban Scarlett 2014 Jeep Cherokee Krystal 2004 Volvo S60 Gone '74 Jeep CJ5 '97 Jeep ZJ Laredo Rudolf ‘86 300SDL Bruno '81 300SD Fritzi '84 BMW '92 Subaru '96 Impala SS '71 Buick GS conv '67 GTO conv '63 Corvair conv '57 Nomad |
#8
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LOL, that's true. The guys I deal with usually have a pretty good idea how far to go before they need to give me a call.
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#9
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I too have noticed a really extreme decrease in fuel economy when the A/C is on although I don't really have exact numbers. I have taken to using a ULSD/BioDiesel blend to help with the lubricity issue. Any thoughts on that?
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#10
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The AC will reduce your mileage somewhat, but it shouldn't be 8-9 mpg, maybe 2-3 mpg. Using bio-diesel will also reduce your mileage. IMHO, using bio-diesel for "the lubricity issue" is unnecessary.
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#11
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Well truth be told I use it to feel better about the environment and keeping my money in my own economy too but I felt like the added lubrication just made it even more of good thing. |
#12
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Even though ULSD has no lubricity issues.
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#13
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I was told by a long time diesel mechanic (and head of the diesel/heavy machinery dept at the local tech college) that ULSD does provide less lubricity and that as little as 2% biodiesel returns the fuel to an acceptable level. This guy knew what he was talking about inside and out.
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1979 240D w/4 Speed Manual, Light Blue Estimated 225-275K Miles - "Lil' Chugs"
Sold but fondly remembered: 1981 300TD Turbo Tan 235K miles, 1983 300SD Astral Silver 224K miles |
#14
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Nothing wrong with using bio-diesel, but you certainly don't need it for lubricity. You will lose some mileage though.
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#15
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Refer to the other 2 million threads on this subject, these "old mechanic" tales die hard.
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