Drain oil when oil is hot or cold??

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Dec 4, 2004
Lexington, KY
I have always drained my oil/changed filter on my 95 BMW 525i when the engine is warm to hot. I usually let it sit for about 1/2 hour to drain as much out of the engine as possible. My filter is an insert that sits near the top of the engine. Is this the best way? Why not start with a cold engine that has sit overnight and drain. Most of the oil has drained out of the engine. BTW, a quick search did not turn up anything on this subject. However, I am sure I missed somethng.
I drain hot. I feel it gets more out. The only problem is if any wind picks up in my driveway the thinner droplets fly sideways more easily and don't land in the pan.
If you drain it when it is cold solids will settle out of the oil and be left in the pan and other places. By draining hot you suspend and remove as much of this stuff as possible. If you want to let it drain overnight then you will remove even more but I would put a tag on the steering wheel as a reminder that there is no oil in the engine. This probably won't make a significant difference.
I don't like to let the cranckcase drain overnight. I just think the risk of the oil pump losing prime is too great (paranoid). Might not really be an issue today, but I have had Chrysler V8 oil pumps lose prime on me even after a few hours. These were engines in 60's and 70's cars. I guess old fears die hard.
I drain when the engine is hot. I let it sit for 10-15 minutes then pull the drain plug. When it's done draining and starts to drip I pour one quart of cheap motor oil down the crank case to allow any remaining dirty oil from the bottom of the pan to drain out. [ April 17, 2005, 11:42 AM: Message edited by: jeepzj ]
While it is hot and just after you have shut down your engine and then let.......it.........drain. I am absolutely certain this gets more contaminants out (while they are in suspension).
Pscholte, Thats what I did. Drive the car until hot, then drain the old oil. I agree it will remove more solids as they are suspended. I just used Mobil 1 5w40 truck and suv for the first time. Been using Mobil 1 0w40. Been told the 5w40 is be a better oil for my BMW.
Originally posted by mikemc: I let the engine cool for about 30 minutes. Oil is still very warm, but I don't get burned by the headers when replacing oil filter.
Excellent point and a caveat worth noting. Unless you have some very special coveralls or gloves, the positioning of some oil filters (try a 1994 Nissan hardbody truck with the 3.0L engine)(I would hope not any drain plugs are problems) is such that you have no choice but to allow some measure of cooling. You can still drain the pan, though.
I drain cold. Modern high quality oil suspends insolubles just fine, hot or cold. Draining cold allows me to do the oil change without using ramps or jacking the car up (I just climb underneath, the clearances are tight, and i'm a pretty skinny guy). Plus cold oil is less likely to be spilled and flows out of the car less quickly if the drain pan isn't quite positioned properly.
Hot as possible, preferrably within a few monites after the engine has been shut off. Just as long as I don't drop the oilpan bolt into a tub of hot oil, I'm good.
I take vehicle out and give a good long run till engine and oil is hot, (not idle it as manual states) then park, by time I get tools and pan organized (ten minutes) then I drain it, let drain full 1/2 hour. Cyprs
When I drain my lawnmower hot, and then the oil sits, I can see a black residue form on the bottom of the jug. From the car, it doesn't do this. I guess the oil filter removes anything big enough to settle out over a few days. So, I drain the car hot or cold.
I drain my hot, as I've done for the last 35++++ years. I feel it holds the contaminents better but I also love the feeling of burning hot oil spilling all over my arms [Big Grin] . When people see the oil burn marks on the arms I just tell people that my wife is doing spousal abuse on me. Boy does she get pi*sed when she finds out I say that [Dummy!] . Whimsey
Maybe it's just my luck but I can't drain when it's hot. Everytime I've tried after a good hours + drive home, I can't get the bolt off. Whether it be the 17mm wrench nut or the allen head hex inside the nut, I can't seem to get that sucker loose without stripping/rounding out the bolt somehow. I've tried even letting it *cool* off for abour 2 hours or so with no luck . I've had 2 HOT OCI with a topsider, and the other 2 cold. How do ya'll get those pesky bolts off when the engine is hot ? I considered the Fumoto valve but after 3 inquiries to them on the correct part # for my application with no response, I gave up on them. My topsider only holds 6 quarts and my sump is 8.5. With the time I spend cleaning the tube, pouring, suction, etc - I've decided to just drain from the bottom. It's less work.
If you are worried about loosing prime after sitting overnight, just unplug the dist and crank the engine a bit before you go to full-start.
Hot. Always hot. Within 20-30 minutes of shutting the motor off. However, I do not preheat the new oil, which someone here confessed doing! [stretch]
Originally posted by mikemc: I let the engine cool for about 30 minutes. Oil is still very warm, but I don't get burned by the headers when replacing oil filter.
Why not just do what I do? I drain it hot, right after shutdown, but let it drain for 60-90min. By the time I get to changing the oil filter, it has cooled down completely.
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