oil capacity question
 

I was changing oil on several of my 4-wheeled conveyances this evening and as they were draining I wondered what purpose the large oil capacity of my 420SEL's engine serves...8 qts vs 4.5 qts in my 5.7L Roadmonster. Is it a cooling issue or a lubrication issue? Does it serve any real purpose at normal US speeds?

Does anyone have a notion as to whether MB gas engines run "clean" or contaminate oil quickly, as opposed to domestic engines. I'm bored on a Saturday night and thought I'd throw these questions out there.

420 SEL is 8.5 quarts it is 8.0 liters

Mine hits the full line on the dipstick with 8 quarts...but either way it's nearly twice the oil the bigger engine in my Buick holds, and oddly enough, the HP and torque ratings are almost identical between the 2 engines. As I recall, they each have 180 HP, give or take, and close to 300 lbs of torque.

maybe for cooling? i have always noticed mercedes has large capacity of oil

the larger oil capacity extends the useful life of the oil because of sheer volumn. it also promotes cooler more temperature stable running by providing additional heat sink area in the oil. and the oil cooler complements it all.

it all adds up and contributes to the overall competence of engineering that results in very long engine life.

tom w

Thanks Tom...I assumed there had to be some cooling issue here, just wasn't sure what.

If, at sustained high RPMs, the pump is taking oil out faster than gravity can pull it back down to the pan, the oil pump will start to suck air and there goes your oil pressure. Having a larger oil reserve helps to avoid this.

A larger sump capacity is always better, the oil stays cooler and cleaner for longer. MB also puts oil coolers on pretty much all of there engines, that alone will prolong there life by a great deal.

Toyota does as well, oil coolers are a very nice touch.

and coolers are not appreciated by a big part of the market, so it is a commitment to engineering excellence not marketing that drives it.

tom w