I've always heard that an engine should be warm before the oil is changed. This seems counter intuitive. During the cooling process the oil has been able to completely drain into the pan. So why warm it up and let the oil settle again? BTW I use 5w20 despite what the manual reflects (0w20). I live in a warm climate.
changing oil in cold engine
- Thread starter RetiredSux
- Start date
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.
So, draining hot ensures that they are in suspension, and allows the oil to drain more quickly.
I've done it both ways. Oil drains slow when cold is all.
I don't think I have ever drained my oil cold. I would like to think that a hot fast drain helps flush out any debris/junk/contaminates.
I've done it both ways and never lost any sleep .
One can always start a cold car for a couple mins before doing oil change.
edyvw
$50 site donor 2025
^This.
You want all contaminants suspended.
I used to prefer cold or warm so I didn't burn myself on the car or oil. I use a MityVac a lot now; get that oil hot for a faster, more complete service.
Does it matter? I say just service that bad boy on a strict schedule and use quality parts.
Does it matter? I say just service that bad boy on a strict schedule and use quality parts.
Is this a real question??
Always, since I was a kid in the 70's, changed the oil when it was " warm". Did change it hot a few times, but then it splashes all over the place coming out, making a total mess. Never changed it cold, just takes too long to drain out IMO.
That's a good idea. Purges out the pan.
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 SS 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 SS 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 SS mixed with HPL Premium Plus PCMO should be okay for a 5k OCI or so.
I don't think it's a huge deal if there's a bit mixed in. Unless you're going so far to drop the pan and I rarely do. The biggest thing for me is just doing the changes when you should be. If it's an unknown-to-me engine I will run a quart or so through of whatever clean oil I have on hand because you just never know in those situations.
I think it's safe to say just about everyone on this forum finds oil changes important and do their best to stay on top of when it needs done in the engines they care about. To that end, it's frequent enough that a bit of old oil from another brand is probably not enough to throw things off in a negative way.
I think it's safe to say just about everyone on this forum finds oil changes important and do their best to stay on top of when it needs done in the engines they care about. To that end, it's frequent enough that a bit of old oil from another brand is probably not enough to throw things off in a negative way.
If you drain the oil cold, be sure to allow for a longer drain time. Cold oil can take a long time to fully drain.
Aarm oil keeps more stuff in suspension than cold oil. as oil cools, if there's too much contaminants to handle, they will be deposited on the engine metal surfaces. Obviously this is more of a concern if your oci is a bit longer than it should be. In that case draining cold means you only partially remove the byproducts and contaminate your new oil more the first time you run the engine.
For me it's not the hot oil, rather the hot oil filter that's a PIA to deal with. If it's too hot to hold in my hand that's a problem.
I could drain the oil hot and wait an hour for the filter to cool. But would prefer to just keep going with an oil change once I start.
I could drain the oil hot and wait an hour for the filter to cool. But would prefer to just keep going with an oil change once I start.
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