Maximum MPG out of a diesel

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Why? I would think the stone cold gasser might burn more fuel, thus cost more for that 5 miles drive. Not sure on the age of this diesel, but the gassers often ran rich initially to get the cat to warm up faster.
If it's like most EGR equipped passenger car diesels, the failure to warm it up will cause buildup in the intake, sometimes to the point of plugging it up. I don't know how cold the OP's area gets (Brittany, France?), but plugging the MB in in cold weather & using thinner oil will definitely help cold weather MPGs. And slow down the sludge buildup, if it's anything like my '82 W123 300D was.
 

OM605

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Yep, tremendous gains in fuel savings.
Unfortunately it's not legal in all parts of the world, but you can count that an enthusiast will always find a workaround.
I'm doing some research and already have figured an workaround haha. And it will still look stock. All i have to do is plug the vacuum line that commands the EGR and keep the baffle in the intake from closing. That way it will only draw air from the airbox. I'll remove the EGR and clean it, my fear being that the excess crud will keep the EGR slighly open.
 
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OM605

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If it's like most EGR equipped passenger car diesels, the failure to warm it up will cause buildup in the intake, sometimes to the point of plugging it up. I don't know how cold the OP's area gets (Brittany, France?), but plugging the MB in in cold weather & using thinner oil will definitely help cold weather MPGs. And slow down the sludge buildup, if it's anything like my '82 W123 300D was.
The climate isn't cold, temps seldom go below freezing. It's quite similar to Oregon or Wahsington i guess. Quite humid.
 
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I'm doing so research and already have figured an workaround haha. And it will still look stock. All i have to do is plug the vacuum line that commands the EGR and keep the baffle in the intake from closing. That way it will only draw air from the airbox. I'll remove the EGR and clean it, my fear being that the excess crud will keep the EGR slighly open.
I'd listen to a mechanic though, I read somewhere on the web that it should be done carefully or else you could risk damage the engine.
 

OM605

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I'd listen to a mechanic though, I read somewhere on the web that it should be done carefully or else you could risk damage the engine.
I went and checked and the vacuum line going to the EGR was already disconnected from a previous owner. I also plugged the line that controls the flap, it should stay fully open at all time since air can only be drown from the airbox. I remember that my other Mercedes NA diesels had this mod. Maybe i'll recover a bit of power and fuel economy.
 

OM605

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Something else i've noticed, the fan clutch seems to grip a lot, the fan it not very easy to turn by hand and it really sounds like a semi truck, there could be loss here too and room for improvement...
 
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For obvious reasons, fuel economy is more important than ever. I am hypermiling as much as i can but have only owned gas cars for the past few years. Now i'm trying to squeeze every km i can out of each tank in this thing: https://bobistheoilguy.com/forums/threads/my-new-horrible-beater.361149/

What i've done so far is the basic stuff: new air filter, new 15W40, high tire pressure. How many of you have experienced increased fuel mileage out of switching to synthetic/lower viscosity fluids specificaly in your diesel cars or trucks? I'm asking about older IDI diesels. I'd switch to 10W30 HDEO, synthetic ATF and synthetic lower viscosty gear oil.

I'm also tempted to rebuild the injectors since i have a bit of white smoke on startup, maybe clean the pre chambers as well. Can you get extra mpg by rebuilding the injectors? To the diesel guys out there, you are welcomed to chime in. 😀
Well I’m a Process Operator in Oil/Gas and what I know vs say in India etc. We have lower sulfur diesel which also accounts to for some odd reason. Less run time on the 2 oil/kero. Diesel from say 15 years ago would lube better and give better performance.
IMHO They should have just increased filtration vs change make up. Diesel has lost its lubricant properties greatly. At most it’s as dry as gasoline with 2 extra overdoses of an upper cylinder lubricant.
I’ll never buy a modern diesel because folks are spending more down time than ever before. Pre 2008 or bust.
 
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I went and checked and the vacuum line going to the EGR was already disconnected from a previous owner. I also plugged the line that controls the flap, it should stay fully open at all time since air can only be drown from the airbox. I remember that my other Mercedes NA diesels had this mod. Maybe i'll recover a bit of power and fuel economy.
Your better off just blocking EGR vs removing vacuum. Unless your EGR completely seals off. It can still pull vacuum from manifold
 
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I plugged the vacuum line to the EGR on a gas engine back in the '70's because when you stepped on the gas the engine hesitated and fell on it's face before taking off. This was a 350 CI engine in a '77 Buick Regal. Prior to plugging the line I was getting about 12 MPG in everyday driving. After plugging the line MPG went to about 15 MPG. I plugged the line using a pencil eraser then put the line back on the nipple on the EGR. The only way to see it was plugged was remove the line and look in it.
 
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I plugged the vacuum line to the EGR on a gas engine back in the '70's because when you stepped on the gas the engine hesitated and fell on it's face before taking off. This was a 350 CI engine in a '77 Buick Regal. Prior to plugging the line I was getting about 12 MPG in everyday driving. After plugging the line MPG went to about 15 MPG. I plugged the line using a pencil eraser then put the line back on the nipple on the EGR. The only way to see it was plugged was remove the line and look in it.
Yeah 3 miles versus coating your intake manifold in oil causing carbon build up. Isn’t enough to run an EGR. MAYBE say an extra 10-15 miles but. Hey up to you.
 
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If the injectors are clogged, rebuilding them will clean them up and flow more fuel. Mileage may drop but you will have more power.

The injection pump controls the fuel delivery quantity, not the injectors.

Rebuilding injectors will do little for fuel economy unless they are so bad they are dripping. For rough running issues, smoke issues, things of that nature rebuilding the injectors can help tremendously, assuming it is done correctly. Nobody is “rebuilding”injectors for $200 and doing it correctly.
 

OM605

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The injection pump controls the fuel delivery quantity, not the injectors.

Rebuilding injectors will do little for fuel economy unless they are so bad they are dripping. For rough running issues, smoke issues, things of that nature rebuilding the injectors can help tremendously, assuming it is done correctly. Nobody is “rebuilding”injectors for $200 and doing it correctly.
A friend has an injector release pressure tester and i would use monarch nozzles if possible, Bosch if i can't.
 
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If you can find it, take a look at the efficiency graph of your engine and it's BSFC. Maybe this can help you determine the proper speeds and loads.

Disabling the EGR often improves efficiency. But not always. Some engines have injection timing that is altered to accommodate the high EGR flow. One thing is clear, today's best "on road" modern diesel engines with cooled EGR systems and DPF are nearly all pushing 44% thermally efficient. That is exactly the number achieved before all this "tech" in the late 1990's.


Good turbocharging, proper injection timing, and unrestrictive intake and exhaust are all important factors in modern diesel engines.

3-s2.0-B9780857095220500091-f09-10-9780857095220.gif
 

OM605

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Drove a diesel VW Rabbit that got 54 mpg on a trip.
My father used to own a 80s Golf II diesel and i remember that he loved that car because nothing on the road gave such good fuel economy according to him. I kinda remember driving for hours and we were looking at the fuel gauge thinking the fuel level sender was defective. But the other cars we owned at the time were a 1970 Mercedes 280 SE and a Pontiac Trans Sport with the 3800 V6. They weren't hard to beat fuel economy-wise LOL.
 
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My kid's learning to drive and my Prius prime is very good at reporting consumption of both gas and electricity.

He goes the speed limit. That's one of us, LOL.

My car goes significantly further on a charge with him behind the wheel. Wind resistance is definitely a thing. Since diesels don't have throttle pumping losses, going slower-- significantly slower-- will gain you mileage.

So also will preheating, assuming you can get the fuel to pre-heat more cheaply than you can just buy diesel.
 
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