fuel usage at idle, 300 SDL - PeachParts Mercedes-Benz Forum

kilboj · #1 12-25-2007, 07:14 PM

Aside from the PC and global warming aspect, how much diesel fuel can I expect to burn leaving my 1987 300 SDL idling in the cold Maine nights, or days when I go shopping or whatever? Does idling hurt anything? It seems content enough the 20 minutes or so I have tried it.

Tx.

John

bustedbenz · #2 12-25-2007, 07:39 PM

I don't personally think it would hurt it a bit.

And this is my ballpark guess... I'd say you'll burn less than two gallons on an overnight idle. Probably less.

I've idled mine for an hour or a little more with no ill effects.

Car security is more valuable than any other concern in this argument. Make sure you can lock it with the other key.

#3 12-25-2007, 07:45 PM

It will burn a little less than 0.2gallons per hour.

Theft should be your primary concern above all else. Other than that it should be fine.

abbamovers · #4 12-25-2007, 08:04 PM

Hate to burst your bubble but excessive idling can hurt your engine.
Diesels like, no, love to be run hard .
The cylinders use the combustion pressure to help seal the rings to the cyl. wall through little passages in the piston.
If allowed to idle that pressure is reduced and can cause blowby.
This blowby allows oil past the rings and when burned causes heavy carbon deposits thus coating valves, injector tips , plugging of those little passages in the piston and scoring the cyl. walls causing less ring sealage.
Also vice versa unburnt fuel can get past the rings and contaminate the oil in the sump , diluting it causing some bearing scoring and other internal wear although diesel fuel is still a light oil and should provide some measure of lube.
Can you imagine if you were using 100 % veggie oil you get carmelization in the bottom end, one big sticky gooey mess.
Thats why a lot of the big trucks use a separate heating system like an Espar heater combo air con generator system when they will encounter prolonged idle times.
I would idle no longer than 5-10 min in the winter even far less in warmer weather and maybe idle about 5 minutes before shut down after a hard run to allow the turbo to wind down and keep oil flowing to pull the heat from the turbo bearings so they do not get burnt and coked up.
Some others may chime in with other suggestions but so far knock on wood I have a little oil burning and a small amount blowby with over 420,000 km on my 1983 300D.
As they say,give it an Italian tune up and drive it like you stole it.

.

Skid Row Joe · #5 12-25-2007, 08:05 PM

Diesel autos.........especially 20+ years old, are hot theft items. Be careful that you're not being followed, and leave it unlocked.

Rich1Merc · #6 12-25-2007, 08:06 PM

I'm not an expert and I have no scientific knowledge about rate of burn on an idling engine. But here is what I actually experienced with 3 different MB diesels at idle using only Diesel Purge to clean the injectors .
Car 1: 1984 240D: one pint of Diesel Purge: Yes I know this is not diesel fuel, and yes I know it is not the same car as was in the thread. but it used up the pint in about 15 or 20 minutes to the best of my recollection.
Car 2: 1976 300D, I put two cans of Diesel purge in a bottle and drove the car around a little and probably ran it for about 20 minutes or so.
1984 300D TurboDiesel: Ran one can through blasting around the neighborhood and I believe it lasted about 15 minutes or so.
Sorry I don't have exact figures, and I also guess that there is a lot less energy per pound in the Diesel purge vs pump Diesel fuel.

Running the car overnight is probably ok for an emergency, but I would imagine the more sensible and more economical thing to do, and more engine preserving thing to do, and less polluting thing to do, (did I get enough of the to do's?) would be to install an engine block heater, cover the engine with a blanket and leave one corner of the blanket sticking out from the hood by the driver's side windshield wiper as a visual clue NOT TO START the engine until you remove the blanket. Use Cold flow fuel additive as well. Hope this helps.
Rich

LNGfish · #7 12-25-2007, 08:33 PM

If it were me I would not idle any longer than necessary for reasons stated above, ie blowby, etc, etc

pawoSD · #8 12-25-2007, 08:39 PM

These engines/cars used in taxi service seem to have no issues over the 400-700,000+ miles they last, and I bet they idle allll the time. So its probably no big deal. With a working T-stat, my engine stays right at 85-86C even if idling in cold weather for hours....lets off a puff of smoke when I drive away after a real long idle, but no other issues. If done regularly I'd shorten the oil change interval accordingly though...to account for the extra run time hours and additional soot in the oil as well as the operation with little load on the motor.

bustedbenz · #9 12-25-2007, 08:45 PM

I guess the way I look at it is that if big trucks can do it and John Deeres can do it, we aren't any different fundamentally.

Jeremy5848 · #10 12-25-2007, 08:53 PM

The fuel consumption gauge on my '96 E300D indicates about a quart an hour at idle.

Jeremy

pawoSD · #11 12-25-2007, 08:56 PM

Quote:

Originally Posted by Jeremy5848

The fuel consumption gauge on my '96 E300D indicates about a quart an hour at idle.

Jeremy

Fuel consumption gauge? Do explain....that'd be a neat thing to have...it'd probably help me not be such a lead foot!

Skid Row Joe · #12 12-25-2007, 10:41 PM

Quote:

Originally Posted by pawoSD

These engines/cars used in taxi service seem to have no issues over the 400-700,000+ miles they last,.......

Not exactly. All those famous MB diesel taxis overseas with all those miles on them, have gone through multiple engine blocks, and or overhauls.

TheDon · #13 12-25-2007, 10:54 PM

Quote:

Originally Posted by bustedbenz

I guess the way I look at it is that if big trucks can do it and John Deeres can do it, we aren't any different fundamentally.

most big rigs now have an APU(aux power unit) on the frame so the big engine isn't belching pollutants.. They have HVAC for the cab so its all good. I've noticed a lot of the newer rigs have them.. they might be optional since I have seen some retrofitted onto older trucks.. ForcedInduction would know more on that subject..

babymog · #14 12-25-2007, 10:55 PM

Good point. And since Detroit diesel, Caterpillar, Cummins, and Mercedes-Benz say NO to extended idling, I'd follow their recommendation and shut down. A need is a need however, and many engines are left idling for hours and even days when necessary, whether that shortens their life measurably is tough to say. Have to do what you have to do.

As to the question on how much they use, I don't know.

Double-plug it if it won't start easily, a healthy engine should be fine. Carry a jumper box in the trunk if you're concerned about battery power, the faster it cranks the better chance you have. Synthetic oil helps cranking speeds too, and be sure you have winter fuel.

Quote:

Originally Posted by bustedbenz

I guess the way I look at it is that if big trucks can do it and John Deeres can do it, we aren't any different fundamentally.

Jeremy5848 · #15 12-25-2007, 11:13 PM

Quote:

Originally Posted by pawoSD

Fuel consumption gauge? Do explain....that'd be a neat thing to have...it'd probably help me not be such a lead foot!

It is one of the features of the ScanGaugeII that I recently bought and put on my wife's 1996 E300D. It plugs into the OBDII port that all 1996 and later cars have. It gives you a bunch of gauge readouts, a trip meter that includes MPG and gallons/hour (and Metric equivalents), and the ability to read and clear error codes.

ScanGaugeII

You also have the ability to program additional readouts into it (but obviously it can display only those things that are available via the car's OBDII port). One nice ability is manifold pressure, aka "boost" (nice for the '98-99 turbo diesels, at least).

It's small enough to velcro onto the top of the steering column in front of the gauge cluster without getting in the way of anything.

It can do "miles 'til empty" sorts of calculations, based on what it has learned from the previous fillup, as well as calculating how much each mile costs, how much of the current tank of fuel you've burned (miles, gallons, dollars).

It's powered from the OBDII port and also has a small internal battery that you can use for checks of the system when the car is turned off, reviewing old data, updating after filling the fuel tank, etc.

List price is $170; I got mine for $160 from an eBay seller with free shipping.

The usual disclaimer: I am not related in any way, except as a customer, to the people who make and/or sell the ScanGaugeII.

Jeremy