changing oil in cold engine

maraakate said:
If it really bothers you on a cold drain, I have just left the drain plug out and poured some small amount of fresh oil until that comes out as well to help purge it.
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Drained oil cold again - far from the first time and I have tossed a quart of useless oil in before as well (always comes out immediately) …
Today I took samples: new oil - flush quart oil - dirty oil:

IMG_1824.webp
 
I drain it hot, full operating temp. I don’t get burned because I have thick rubber gloves. PPE is pretty amazing stuff.

None of my vehicles have drain plugs anymore, they’re all valves setups like Fumoto or a Stahlbus.

I then let it sit a cool and drip for 30 min or so. I dump in a quart of flush oil (or more) until the drain oil comes out clean. Then I change the filter.
 
Hohn said:
I drain it hot, full operating temp. I don’t get burned because I have thick rubber gloves. PPE is pretty amazing stuff.

None of my vehicles have drain plugs anymore, they’re all valves setups like Fumoto or a Stahlbus.

I then let it sit a cool and drip for 30 min or so. I dump in a quart of flush oil (or more) until the drain oil comes out clean. Then I change the filter.
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Oh yeah? Well, hey dude - I heat up that flush oil !
J/K … this is one of the silliest topics on this site …
 
4WD said:
Oh yeah? Well, hey dude - I heat up that flush oil !
J/K … this is one of the silliest topics on this site …
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Yeah, I gotta be honest... I think its safe to say everyone on this site cares about their maintenance more than the average person but people been draining oil hot or cold for a long time and no issues. If it makes you sleep better at night to do it one way vs the other OK.
 
4WD said:
No - just wanted to visualize if draining cold was really inefficient - I don’t think the flush oil picked up much - so cold, warm, or hot only 😵‍💫
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I don't see why the "flush" oil would pick up much at all. It goes straight from the head to the sump, while the trapped oil is in the galleries, the crank, oil pump, etc. all of which is completely isolated from the "flush".
 
Astro14 said:
I don't see why the "flush" oil would pick up much at all. It goes straight from the head to the sump, while the trapped oil is in the galleries, the crank, oil pump, etc. all of which is completely isolated from the "flush".
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I know that - That’s just a word - call it a tracer - whatever - the point is there way too much back and forth about falling out of suspension and all that - I think it’s allot of hot air over hot oil … I see clean oil when I do this hot too … Going back to come off high idle - up on ramps - change oil.
 
rstcso said:
Everybody's favorite Motor Oil Geek recommends pouring a quart of new oil through the system after draining the old whenever you're changing from one brand to another to help get some of the old oil flushed out of the pan. I did this when I changed to AMSOIL Signature Series from the OEM fill on the Honda. I'm undecided whether I'll be doing it in a couple of weeks when I switch from AMSOIL Signature Series to HPL Premium Plus PCMO. An oil and filter change requires 5.8 quarts, and I have four cases of HPL. If I use a quart as a flush, I'm going to be short a quart for a long, long time (unless I order more).

FYI, the UOA after the switch showed some Honda oil was still in the system and mixed with the Amsoil, anyway. A little AMSOIL Signature Series mixed with HPL Premium Plus PCMO should be okay for a 5k OCI or so.
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On my last oil change, I used Amsoil engine flush on the existing Valvoline Restore and Protect. Let that mixture idle for 15 minutes and drained completely. Changed filter (to cheapest Supertech filter) and refilled with Supertech synthetic oil, drove around for 15 minutes, completely drained that. Changed filter again to MicroGard Select and refilled with Amsoil Signature Series. I'm sure that didn't get every drop of old, dirty oil and debris out, but I figure it gave me a pretty clean new start. Going forward, I plan to warm up engine, maybe drive around the block, then do a simple drain and fill.
 
Astro14 said:
As the oil cools, contaminants might precipitate out. A cold drain would leave them in the pan.

So, draining hot ensures that they are in suspension, and allows the oil to drain more quickly.
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What is the percentage of that precipitation in a real world ? "Might" is a very broad statement IMW
 
rstcso said:
Everybody's favorite Motor Oil Geek recommends pouring a quart of new oil through the system after draining the old whenever you're changing from one brand to another to help get some of the old oil flushed out of the pan.
Click to expand...

I think it's more important to make sure the vehicle's oil pan is leveled or angled such that as much oil as possible is drained without leaving any residual. Also, if time allows, let it drain until every drop is done draining. I have let mine drain overnight in the garage.
 
I do a lot of oil changes, done it both ways, don't really think it makes any difference. My last oil change, done about 2 hours ago, was cold oil, on a Volvo truck. I wasn't going to start it in the shop, and let it run. I told the driver when he got back, to put it in the shop for a service. His paperwork shows he parked it about 1:40 am this morning, and I removed its drain plug about 7am, put the drain plug back in about 10am. For those who think I did it wrong, oh well.
 
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