Is the oil cooler *really* necessary?
 

Y'all,

I know that such an impertinent, provocative, and sacrilegious question is sure to get MB believers riled-up, but my question is a serious one. My '84 300td will never see autobahn or track use, and unlikely to see anything more than the lightest of towing. Given my experience with oil temperatures on other vehicles, I can't see how it's really necessary for my 300td. The lines are leaky on my 300td, so I'm seriously considering deleting it and looping or otherwise bypassing/removing the circuit. FWIW, I will keep the parts and ensure that any modifications are reversible.

So, does anyone have actual experience with the necessity of these for normal commuting use? By "actual experience," I mean actual observance of oil temperatures on a gauge.

Sorry, but answers like "MB put it on, so it's necessary," "I have heard they are good to have," or "If you move to Saudi Arabia, you will need it" aren't arguments I'll consider valid. :wacko:

Thanks in advance,
Shawn

One previous SDL owner noticed higher temps without.

You do drive on the freeway right?

Lines are maybe $100, you'll spend a good amount of time trying to bypass and remove versus replacing the lines.

Just my 2¢

My 85 307d which was a 22' class A motorhome built on the 307d chassis with the 616 engine never had an oil cooler. I sold it at about 128k miles. While it was only driven the Europe, the loads what engine saw were way higher than anything a 240d will see. So, no it isn't necessary.
I suspect that the oil cooler installation may have been correlated with air conditioning.

Stop and go driving in high ambient temperatures is far more "severe" than open road driving. (Which is not to say that you ever experience either hot weather or slow-moving traffic in your location!!!)

What is the highest oil temperature that you consider acceptable?

The SD hasn't had one since October, havn't noticed anything.

But yeah it helps the engine a lot, and I wouldn't get rid of it unless the car is a total beater you plan on dumping in a couple of years.

An oil cooler is the best thing that can be added to an engine.

I didn't expect to see no increase in temperature. Sure, I drive on the freeway, but unless I can say that there's a meaningful difference, I can't tell if the cooler is really necessary. $100 isn't much, but that's about 8% of what I paid for the car. I spent a good bit more than that on brakes and headlights, but the necessity/gains in those areas are substantial and noticeable.

Sure, I understand that stop-and-go driving is more "severe," but IIRC the oil cooler only gets air flow when the car is moving (unless you count backflow from the engine-driven fan as the hot engine compartment air flows out), so it probably doesn't do much good in traffic. The engine isn't producing much power in those conditions anyhow. FWIW, I live in the Atlanta area.

The highest oil temp I'd consider "acceptable" would be around 220F/105C. I guess I can block the oil cooler airflow and observe the temps on my (upcoming) oil temp gauge. Yes, I understand I could replace the lines for only a bit more $ than what the gauge is going to cost me, but the gauge is a necessity, IMO, and can also be removed and transferred to another future vehicle.

The thermostat in the oil filter housing does not open until 110*c.

So, that should answer the question as yes, the oil cooler is needed, since it opens 5 degrees C above your "acceptable" range.

The oil cooler is there to cool the oil. Turbo engines tend to run hotter then NA engines. Cooler oil does not suffer from heat related breakdown as quickly.

It's the turbo and the piston cooling jets that add too much heat to your oil. You probably don't need one without a turbo (although my NA 606 has one).

Excellent info -- thanks!

All that says is that MB thinks no cooling is necessary up to that point. Nobody has come through with any quantitative evidence for any observed temperatures at any driving conditions. What it does tell me, though, is that if I don't ever see that temperature during the worst conditions I expect to encounter, I can remove it with no ill effect.

Yeah, yeah -- I already understood all that.

Highest of 105C is dangerous. You want your lowest operating oil temperature to be about that. It is essential that the oil regularly exceed the boiling temperature of water.

This thread is pointless......Do whatever you want to your car, besides, your the "engineer" figure it out.

OK, whatever. :1blank: The "point" is to determine whether I "want" to do this, based on information gathered. Saying I'm considering doing something isn't the same thing as wanting to do it. Perhaps you don't understand the nuance.

You are correct that I'm an engineer, though! :cool:

Yeah, well since MB did not give us an oil temp guage, then we'll never really know the true temp of the oil itself..

The oil cooler helps the cooling system be more efficient also. My gasser '77 Chevy p/u had a factory oil cooler as well. A friend of mine had one without it. My engine temps were 15-20 degrees less than his. My engine did not need a rebuild, nor did it tap, burn oil or run rough, even at 200K miles. My friends needed a rebuild at 130K miles. It spun a rod bearing.

But, it's your car to do as you wish. It will be good info to know how your engine temps hold up, cause a new cooler is really pricey!

Just about everything I have ever driven has an oil cooler. I think it's a german thing.

220 is a good oil temp, 240 is a little hot, 280 is too hot. Ask me how I know? Well... Porsches, VW's, etc.

In a water cooled engine, it's unlikly you'll ever see 280 on the oil temp guage, unless you're racing, or your radiator is dry. Water is the primary coolant in water cooled cars. They cool the oil because with piston squirters and turbo's, it can get too hot. A simple cooler solves that.

If you're going to putter around, I can't see how disconnecting the oil cooler will matter. If you're in the desert, or autobahn, or maybe a three hour cruise, then it may matter. I'd bypass the cooler in a pinch, otherwise, I'd fix the hoses.