I like in Washington State (not exactly the tropics) and my oil cooler and lines get warm after the car reaches operating temperature. From this I can deduce that it does come into use during normal operating conditions.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Seems like a perfect analogy to me.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Many oil thermostats intentionally provide a small amount of flow at all times so that an air bubble doesn't get stuck in the cooler (as might happen if the cooler drains or is drained during an oil change), so I can buy what you're saying.

As I said earlier, the oil cooler feels only about 20 degrees warmer than ambient after doing 75 mph for 30 miles (and the car's not overcooling either, as it's running at 90C with no fan). I haven't checked it after being in slow traffic, though, but backflow from the engine compartment air would heat it up and give erroneous results. It'll have to be checked "at the source" with an oil temperature gauge.

It is interesting that you insist on "hard facts" from the forum, but at the same time you perfectly willing to put forth generalizations such as this.

Your theory happens to be invalid in the case of the 617 engine. I suspect that you won't believe that until you install a flow meter in the oil cooler supply line!!! And it would probalby be a good idea to install a check valve in the cooler return line, just to rule out the possibility of a pesky backflow condition.

I can drive 75 on the freeway for 20 mins when its 10-15F outside and my oil cooler is VERY warm/hot after doing so. When its above 10F outside and I drive longer than 10 minutes...my oil cooler is always very warm to hot in temperature. I think that alone proves how much it is used. I want my engine to last a long time, so I replace everything and keep it how the engineers intended.

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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)

Don't forget, the flow in the oil cooler goes from the bottom-up. If you are feeling the top of the cooler, it's AFTER the oil has been cooled.

Or heated, depending on whether you buy the convective backfkow theory!!!

BTW, the oil cooler is thermostatically controlled.

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DDC/MTU....Setting the pace
1985 300cd
1983 300d...aka "The Yummymummymobile"....Wifes ride
2006 Wesmac 38' Sportfisherman, Single DDC/MTU 12V-2000 1500 hp

You have currently replaced John Forbes Kerry as a recipient for "The Village Idiot Award."

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DDC/MTU....Setting the pace
1985 300cd
1983 300d...aka "The Yummymummymobile"....Wifes ride
2006 Wesmac 38' Sportfisherman, Single DDC/MTU 12V-2000 1500 hp

I have posted questions here before and have never boasted of being an engineer. If Shawn wants to remove his oil cooler by all means let him. It is one of those situations of "If you already know the outcome, why question the process" or "if you already know the answer then why ask the question". I don't think he is looking for confirmation of his idea, rather letting us know since he is an "engineer" then we must agree or argue. A little juvenile for an engineer I would think.
Bud

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1987 300D Turbo, 175k mi., 1998 BMW 323i Convertible, 1997 F250 4x4 7.3L PSD

People seem to be a little harsh given the honest questions. I think there is real reason to doubt the necessity of the oil cooler on the 616 or 617 NA under some conditions. If it is necessary under all conditions, why did MB sell hundreds of thousands of trucks designed for heavy duty work in Europe with a 616 and no oil cooler? Can't we appeal to the authority of the MB engineers who made this decision in the same way people are claiming the authority of the MB engineers who put the oil cooler on in other applications?

If MB decides the oil cooler is not necessary under some conditions, who are we to argue with them?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

any of us can be guilty of pride.

no matter what our profession.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Just looked up the topic in my shop manual. 615 engines only had oil coolers if it had AC. 616 had oil coolers standard until 1978. After 1978 oil coolers only installed on 616 if they had AC. 617's always had oil coolers.

In looking at the diagram in the shop manual, it looks to me as though once the thermostat opens, it permits oil to flow both up into the filter and out to the cooler. It states "In the end position (with the thermostat open) the direct flow th comination fileter elemens is closed escept for a given quantity of oil. this oil quantity is enough to guaranett lubrication of engine at low outside temperatures, when the through-flow in oil cooler is considerable detained by the now viscous oil. The major oil quantity arrives at air oil cooler where it is cooled and then flows back to oil filter housing the through oilter filter housing from outside in"

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Kerry,

I had a 1983 240D 4 speed with a/c, I don't recall seeing a oil cooler in it, maybe my oversight.

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99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT

one word. yes.