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Old 10-18-2017, 01:11 AM   #1
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Oil change trivial pursuit question

Well, one for the future anyway.

I have just changed the oil in my Lehman SP130s. Nothing unusual about that for most of us.

I sucked it up through the did stick hole, Once again nothing out of the ordinary. What leads to the trivial pursuit question is next..............

I decided to add the flexible hoses that screw into the sump plug hole and allows the old oil to be sucked from the lowest point of the sump (for subsequent changes).

To save a bit of mess as I figured there would be some oil left in the sump due to its angle, I put a catch container under the sump - I was very surprised when 2Litres (about a quart)came out and thus the trivial pursuit question......

How much oil is left in the sump when oil is sucked up via the dipstick hole............Answer 2 L or about a quart.

I guess it explains why new oil starts to go dark pretty quickly - amongst other things its mixing with 2L of old black oil.


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Old 10-18-2017, 01:14 AM   #2
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Even when sucking it through the drain hole the oil in mine turns dark very quickly.

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Old 10-18-2017, 01:32 AM   #3
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I had the problem of retained dirty oil when doing my own changes. Last time I had the marina mechanic do it. He leaves a suction oil removal pump connected overnight. Very effective, oil relatively clean 80 hours later.
From memory one TFer, FF I think,thought this process removed too much oil leading to an unlubricated start after refilling. I prefer what is probably the dirtiest 2L comes out, but I mention it in fairness.
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Old 10-18-2017, 03:01 AM   #4
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Well, as we know, oil needs to be at least warm if not hot when extracting it from engine so it will become thinner and enable us extract almost all dirt with it. Of course, this means that we are going to run the engine prior to oil change. Then again, when you need to measure the oil level, you measure it in the morning after the engine is not being run for at least over night so that all oil is being returned to the sump and the bigger the engine the longer will it take. So, therefore is the difference I presume. So, it makes sense that it will be a bit harder start on engine if you take it all out, but for oil it will be better to be clean, so it is compromise and do what you prefer. My procedure after oil change to prevent harsh start on engine is to disable positive wire from fuel shut off valve and crank the engine until the oil pressure does not show up, then I reconnect the wire and fire up the engine. Then again, this procedure is hard on starter and battery so you should not crank the engine for longer than 15-30 seconds without at least 1-2 minutes pause between cranking if so needed. There is always something and the list can go on indefinitely (i.e. now add oil filter to the procedure,...).

Anyway, you will most definitively better extract oil by taking it from the bottom of sump.
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Old 10-18-2017, 05:17 AM   #5
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"Anyway, you will most definitively better extract oil by taking it from the bottom of sump."

There are special valves made to make this a safe operation.

They replace the bottom drain fitting.

AS long as the oil pump is covered when the oil is refreshed taking ALL the oil out is no hassle.

Oil pumps are positive displacement , so fill the passages rapidly.

The engine needs to be hot to change the oil, and wont cool much in the time it takes to change ,

on restarting the engine parts will still have an oil film so no wear is created.
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Old 10-18-2017, 06:17 AM   #6
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2 liters is closer to 2 quarts right?
The change in color from leftover oil would be apparent after 2 minutes of running. It only needs a good mixing warm or cold.
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Old 10-18-2017, 06:35 AM   #7
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City: Quebec
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In my engine I am able to remove 5 to 6 liters of used oil by pumping from the dipstick hole. The engine contains around 8 liters of oil.
I wish the builder had installed a hose on the drain fitting now it would be quite difficult to do it.


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