I searched the archives for an answer to this question. Found two that both said to check engine oil level when engine was warm.

If an engine is stone cold(left sitting overnight), wouldn't ALL of the oil have settled to the bottom, thereby providing the
most accurate reading?

I suppose my problem is partly due to age.
I was taught years ago to always let the vehicle sit overnight, then check on a level
surface. Would appreciate some insight into this "check warm" philospohy. Thanks for your time.

Mike Murrell
Boerne Texas
'91 300-SEL
M103 engine

Mike, generally folks don't like to wait for an overnight to check in AM, but if logic serves me, the longer you wait the better. However, having said that, there is the consideration that when an engine is warm, things will settle quicker, but, there will always be some oil tucked away somewhere. At any rate, either way will work. You're trying to differentiate between rather small quantities of lubricant. So check it in whatever fashion you are comfortable with. I suppose someone has done a white paper about this issue, but personally, I don't think it's really all that important. I would find something else to be compulsive about, like changing the oil every 3,000 miles.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

I change it every 1,500 miles. Oil breaks down a great deal between 2000-3000 miles.

Doesn't get any better than that..

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Jeff L
1987 300e
1989 300e
1987 BMW 325

Mike Murrell,

My Man!!!! You definitely got it figured out.

Change oil hot and change oil often.

I don't have to wish you good luck, you're making your own luck with frequent oil changes.



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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

About that "White Paper" study on this subject. I'm sure our government has spent millions of $ in grants only to find in a 24-hour period, about 3.703923019 ounces of oil will have dripped down to the oil pan.

A bit o' humor for the day

Brian

Larry - You are ABSOLUTELY right..change the
oil when it's HOT. All the sludge/junk washes out. My MB car is a low mileage vehicle; however, I have an old Toyota truck and an Accord that collectively have about 550,000 mi. on them. When I pull the valve covers off, you'd swear you were looking at a new head - no sludge - no cam galling - nothing that resembles wear or the kind of mileage I've logged.

Too bad so many folks don't realize that changing the oil when it's hot can add a TON of miles to the life of an engine.

Regards.

Mike Murrell
Boerne Texas
'91 300-SEL

On a slightly different but similar subject, why does an auto transmission dip stick have such a variance between the full hot and full cold line? I realize why it is important to check it with the engine running and in neutral, but why is hot impaortant? Does it expand that much?

Thanx!

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Deezel
87 300TDT
150,000 miles

When cold, some of the ATF will drain out of the converter back into the sump. When hot and running, the converter is full and there is less oil in the sump. The oil doesn't expand that much. The principle here is to make sure there is adequate ATF to completely fill the converter, otherwise, if air gets inside there, it will produce cavitation and will not perform it's intended function. The torque converter is the highest volume resevoir for ATF inside the tranny. Kinda like the engine. When it's running, a good part of the oil is everywhere but in the sump. It's your basic gravity thing...

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Jeff L
1987 300e
1989 300e
1987 BMW 325

[This message has been edited by jeffsr (edited 04-12-2000).]