I am trying to find out the most efficient way to run my '82 300D. I understand that with bigger Diesel engines (big rigs, locomotives), it is more economical to let the engine idle vs. turning it of, and then re-starting it. I understand that the MB 300 Diesel is a far cry from an 8V-92, or something of that nature, but I guess what I'm trying to figure out is as far as fuel consumption, what is the running time in minutes at idle equivalent to starting it up?

If I stop somewhere for less than 10 minutes I leave it running. Providing it is in a good location. Other than that why waste the fuel?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I didn't even know we were supposed to turn these cars off!


Just kidding....I usually leave mine running though, I mean an idling diesel uses so little fuel, so I don't really see it as much of an issue usually....especially in the winter....its cold!

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

A friend from Wisconsin claimed a high school buddy left his VW rabbit diesel running the entire winter!!!

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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6

How did he refuel ? I thought they make you kill the engine when you fill-up.

I always keep her running while I re-fuel. Nobody has ever said anything.

I have never had a problem with that. I worry about the engine getting a dense dose of fuel additive before I start filling than getting yelled at by a clerk.

I have spent many years with large diesels 10 litre and above ; and although at an idle , very little fuel is entering the combustion chamber ,enough to dilute the lubricating oil in the sump would likely be washing down the cylinder walls . With commercial trucks and buses they are shut down after an appropriate cool-down if they were working hard . You would leave them running in very cold weather but idled up with a hand or air throttle .

In the 80s (in Wisconsin) the people next door had a rabit diesel. There was a two week stretch of extreme cold and they never shut it off. Their car would not even think of starting below 10 degrees F.(or at least not without an unhealthy dose of ethyr) The only places you could get diesel then were the truck stops by I94 or at the oil company in Franksville so they had to keep diesel at home.

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1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

An engine not running uses NO fuel, as opposed to an engine idling which is using some fuel. Restarting uses no more fuel than when running, that's an old wives tale.

In addition, due to the lower combustion temperatures of diesels, they are more prone to fuel washing of lube oil from the cylinder walls, significantly increasing wear. There's a phenomenon in large trucks, especially (and maybe limited to) Detroit diesels called wet stacking, whereby unburned fuel mixes with the soot on the stack walls and instead of being expelled into the air, runs down the outside of the stack, looking like oil.

There may be times when it's so cold that you may not be able to restart if it's shut off for an extended period, but as a rule, shut it off.

there are a couple of options for warming your engine when it's not running, electric block heaters, and fuel fired circulation heaters (espar and webasto) for those who don't have access to an electrical outlet.

Happy Motoring

RBM

I won't idle a diesel for a cold start (idle for 10mins before driving). When i Start my diesel I'll idle it for 20 second with my foot off the clutch to get oil circulating in the gearbox then I'm off driving at low load till the engine is up to temp.

As for idling a engine after driving for extened periods I'll idle them for the A/C only, not the heater And even then no more than 5 mins (engine gets too cold in winter).

I do however disconnect the vacuum shutoff when I deliver pizzas and leave the engine running the whole night (6-10pm) while stil being able to lock the car. I only do this to remove any chance of cracking the cylinder head do to heat cycling between deliveries.

Excessive idling of these engines when cold is just unnessary wear. Idling while you are away for 5-10mins is ok, much more than that is excessive unless the weather is extreamely cold (-25C). A good battery, syn oil and good glow plugs will start a healthy engine with a block heater in almost all conditions. If the engine was run in the last few hours then it should start regardless.

I don't have much expereince with such cold weather but I don't see the point in idling cars all winter when a block heater can easily be connected if you are at home.

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Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32

I'm with AusMBTech on this. That's about how long I warm an engine before putting it in gear. If it's really cold I might go just a little bit longer.

There's just no reason at all to leave one of these cars running. I suppose if it's 20 below then you will know if it will restart or not, but under normal circumstances I have never let one run.

Have a great day,

I won't let mine idle for more than a couple minutes. It's simply a waste of fuel and unnecessary wear. From doing Diesel Purging I know these cars use substantial fuel even while idling.

There also seems to be this widespread myth that's it's good to warm up your car in the morning by idling it for a long time. I especially see women doing this and then I hear about their vehicles getting stolen. A car will warm up so much quicker if you just drive it and you'll waste a lot less fuel. As long as you take it easy until the car is warmed up there's no harm done by driving it right away.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Anyone who has done a diesel purge knows that these use fuel when idling. That is a very good way to get a visual idea of how much it uses. I think some might be suprised how much it uses at idle.

**edit**
I think me and DieselAddict were typing at the same time. I concur with him.

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I have no problem letting any of my diesels warm up for 3-5minutes when really cold. Its uncomfortable to get into a freezing cold car and just drive off. While I understand all of the wear issues stated above, for me, comfort is a factor too. I can live with a little extra wear to have heat when I move off in subzero temps. I have let the work truck idle for the entire work day occasionally when I am on a jobsite and temps do not get above 0* all day and I don't have an extension cord long enough. I will also leave the vehicles idling for a couple of minutes if I need to. No big deal and the oil analysis comes back clean every time. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K