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  #16  
Old 08-11-2007, 01:16 PM
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Well, My 560 with 6.0 litre and R-12, really loses a lot of fuel mileage with A/C on. I can drive around and have no probelm with economy. The minute I turn on the A/C, The S.O.B. becomes a gas guzzler all of a sudden. I could possibly be losing 8-9 miles per gallon also by the way it performs. I don't know for sure though, I never did any math on it, but it seems to be that way when just tossing figures around every time I run it and watch my fuel gauge go down..

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  #17  
Old 08-11-2007, 01:29 PM
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Quote:
Originally Posted by chetwesley View Post
This guy knew what he was talking about inside and out.
It's always difficult to discern if the guy knew what he was talking about "inside and out" or whether he believes that he knows what he is talking about "inside and out".

The only way you can discern the difference is if you know what he's talking about............"inside and out".
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  #18  
Old 08-11-2007, 02:18 PM
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Quote:
Originally Posted by GreenSD View Post
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?
Yeah! That's works for me so well that I run biodiesel exclusively now as much as I can! It was not available here in Phoenix yesterday so I'll have to wait until monday! It seems to me though to get back on subject tearget, that 9 MPG loss is rather high! I use R 134 too and my MPG is only at a 2 MPG loss or les! Do you have your system overcharged or maybe a restriction in the expansion valve casing the compresor to work harder?
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  #19  
Old 08-11-2007, 02:27 PM
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I know I lose at least 5mpg with the AC on, and that is with the 300TD and the 240D {Squash}. Can't keep the odo working long enough to get a good reading on China yet.
It could be as much as 8mpg with the wagon, but 5 is definite.
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  #20  
Old 08-11-2007, 02:27 PM
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Doesn't seem to matter much...

MPG decrease with A/C "on" in my '85 (CA version, EGR/ARV removed or defeated, A/C still on native Freon) is minimal and usually covered by other factors such as driving style, load in the vehicle, terrain, etc. Then again, my trap cat-laden 617 engine gets about 24 MPG at best on B100 or dino. Once I have the trap cat replaced with a test pipe (temporarily, for testing purposes only) I may be able to get better data.
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Last edited by Jeremy5848; 08-11-2007 at 02:28 PM. Reason: Add more information
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  #21  
Old 08-11-2007, 02:31 PM
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Quote:
Originally Posted by Jeremy5848 View Post
MPG decrease with A/C "on" in my '85 (CA version, EGR/ARV removed or defeated, A/C still on native Freon) is minimal and usually covered by other factors such as driving style, load in the vehicle, terrain, etc. Then again, my trap cat-laden 617 engine gets about 24 MPG at best on B100 or dino. Once I have the trap cat replaced with a test pipe (temporarily, for testing purposes only) I may be able to get better data.
Sounds to me as if it's a whole lotta trouble to go through, just to test something you can't use on the local streets of Cal. reguardless of the results...Or did I misinterpret something I read..?
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  #22  
Old 08-11-2007, 03:50 PM
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I lose ~3 mpg with ac on.
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  #23  
Old 08-15-2007, 05:57 PM
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Quote:
Originally Posted by BigBadJohn View Post
I usually have them consult me before doing any major work w/o my knowing
True - however in my case I made out a highlevel list for them to go through and check out, and R&R if needed. I feel pretty good about these guys ... apparently he's the only reputable MB mechanic here in on the Gulf Coast (Gulfport, MS). Peterman's Garage - good guys but are always busy and backed up with work.

They did top-off the R134a and added a leak detector to it, but they could have overfilled it I guess.

I am to a slight disadvantage at this stage since I don't have much driving experience with this particular car. I just now started to drive it regularly.

So, to recap over the past few days since I have been away, it's indeed true that I do have approx 8-9 MPG loss when the AC is on. I have tried to drive consistently over the last two tanks (I drive 120 miles a day, 110 of them on the interstate). It maybe one of those things I let slide until next spring - I just have too much on my plate right now. However, if any of you guys live in the area and can spend some time with me - I'll buy the food and drinks!

-graham
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  #24  
Old 08-15-2007, 06:19 PM
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Actually our ULSD stinks...

Quote:
Originally Posted by Craig View Post
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.

According to MB and the engine manufacturers association there is a problem with our diesel fuel. It has no where near the lubricity it should have. In fact it does not even meet the standards the oil companies have set. I have posted the information before on this board. You can also read this in the June issue of "Star Magazine" (the MBCA publication)

They recommend either using 2% bioDiesel or using a lubricity agent to restore the needed lubricity to the fuel.
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  #25  
Old 08-15-2007, 07:43 PM
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George Murphy vs Frank King

Quote:
Originally Posted by LUVMBDiesels View Post
According to MB and the engine manufacturers association there is a problem with our diesel fuel. It has no where near the lubricity it should have. In fact it does not even meet the standards the oil companies have set. I have posted the information before on this board. You can also read this in the June issue of "Star Magazine" (the MBCA publication)

They recommend either using 2% bioDiesel or using a lubricity agent to restore the needed lubricity to the fuel.
I have this issue of the The Star in my living room as I write this and I remember reading George's recommendations and being very confused by them. While George has been a devoted member of the MBCA for a long time, some on this site may recall Frank King who was probably the greatest technical contributor to The Star since its inception.

Anyway, this is not the first time sulfur content of over the road No.2 fuel has been reduced. It was reduced from 1500 ppm (I think) levels to 500 ppm in the early 1990s. At that time, Frank wrote countless reminders in the Star about why this shouldn't concern MB owners. I am looking at page 78 of the July/August 1997 edition on my desk and he wrote the following:

DIESEL FUEL LUBRICITY

Most diesel owners remember the great fluster about the introduction of low-sulfur diesel fuel...wide publicity was given to cases where engines with rotary injection pumps experienced damage caused by the lack of lubrication which was provided by the sulfur. Mercedes-Benz passenger cars use in-line injection pumps and do not depend on sulfur content for pump lubrication...

Now, I don't know if more recent models have different injection pumps which DO rely on sulfur content as a lubricant, but it would seem -- at a minimum -- that anything built prior to 1997 is not a concern. Why George didn't mention this in his article is a mystery to me. Then again, maybe I'm missing something altogether, but the articles seem on the surface to be quite contradictory.
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  #26  
Old 08-15-2007, 08:20 PM
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Quote:
Originally Posted by ftav View Post
DIESEL FUEL LUBRICITY
Most diesel owners remember the great fluster about the introduction of low-sulfur diesel fuel...wide publicity was given to cases where engines with rotary injection pumps experienced damage caused by the lack of lubrication which was provided by the sulfur. Mercedes-Benz passenger cars use in-line injection pumps and do not depend on sulfur content for pump lubrication...
Just curious.. did he ever go into what exactly does lubricate the little cam follower wheel(s?), slide valves and fuel pump piston? From the drawings I've seen of the inside of the IP, they are immersed in diesel fuel, so there's no way anything else can provide lubrication for them.

Perhaps both are right -- 500ppm was plenty enough for lubrication, but the ppm in ULSD is not?

Either way, doesn't sound like it's anything to panic over.. individuals have already driven thousands of miles on ULSD, so if the problem were severe, we'd already know.
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  #27  
Old 08-16-2007, 07:53 AM
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other issues

There were other issues of the Star from the mid to late 90s where Frank weighed in on the subject. i can't find them right now but will keep looking. He might have mentioned more detail in those other articles, but he didn't go into any greater detail in the one I just quoted.
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  #28  
Old 08-16-2007, 02:15 PM
Gene
 
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Yeah, but Forced hates bio, so there you go.

I too suffer a milage loss with AC on. 31 vs 33.5 mpg

BUT ULSD SUCKS for another reason. BTU's . For better or worse, I have at least one cylinder in this Benz that "pings" on straight USLD. Quite horribly I might add. Power Service Cetane boost will work if I put enough in, and then it cuts power dramatically. Hey, not for nothing, but I picked a good 6 cyl twin cam for a reason, not an ancient 4 cyl.

Best fuel has been bio. Even 15% bio in teh tank gives the fuel enough BTU's to run quiet and smooth in this engine. Cant wait until I get a good source of bio, petro diesel is horrible in my ride. I'm trying the blue bottle from Stanadyne now, hope it does better. Only WINGAS cures it though.

I'm sure someone will tell me this is wrong or that is wrong, or Forced will tell me how the engine should run fine on ULSD. FACT: Engine prefers bio.

But 8-9 mpg drop is hairy. Something else is amiss.

Last edited by WINGAS; 08-16-2007 at 02:21 PM.
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  #29  
Old 08-16-2007, 03:13 PM
Craig
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Quote:
Originally Posted by WINGAS View Post
BUT ULSD SUCKS for another reason. BTU's . For better or worse, I have at least one cylinder in this Benz that "pings" on straight USLD. Quite horribly I might add. Power Service Cetane boost will work if I put enough in, and then it cuts power dramatically. Hey, not for nothing, but I picked a good 6 cyl twin cam for a reason, not an ancient 4 cyl.

Best fuel has been bio. Even 15% bio in teh tank gives the fuel enough BTU's to run quiet and smooth in this engine. Cant wait until I get a good source of bio, petro diesel is horrible in my ride. I'm trying the blue bottle from Stanadyne now, hope it does better. Only WINGAS cures it though.

I'm sure someone will tell me this is wrong or that is wrong, or Forced will tell me how the engine should run fine on ULSD. FACT: Engine prefers bio.
I'm sure your engine does run smoother on bio, but let me try to clarify a couple of your "facts."

1. Your "ping" has nothing to do with the heating value of the fuel (BTUs/lb.).

2. ULSD diesel has between 0% and 2% lower heating value than LSD, depending how it was processed.

3. Both LSD and ULSD have a significantly higher heating value than bio.

4. Heating value and cetane are two completely different things, they have nothing to do with each other.

4. Bio has higher cetane than LSD or ULSD.

5. Bio has a lower combustion speed than petro fuel (which has nothing to do with either heating value or cetane).

The fact that your "ping" is worse with petro diesel probably has to do with the lower combustion speed of the bio, running bio is like retarding your IP timing. You really should determine what the problem is and fix it before it gets worse and causes damage. I would not be surprised if you have a bad injector.

The fact that your car "likes" bio better than petro only proves that you have a mechanical problem that is being masked by the combustion characteristics of the bio.

I have nothing against bio, but it's just another fuel; it is not magic and it will not fix your engine. If you are going to be a proponent of these fuels, you really need to do your homework.

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