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I typically will idle my motorcycle's engine for about 10 minutes before changing my motor oil, to warm up the oil, so it flows out better. I never really questioned it.

But my bike's been in storage for longer than usual, and the battery's in repair mode for a day or so -- and I can't run the engine right now. I'm wondering whether it might be just as efficient (or even better) to drain the old oil it while it has gravitated down into the pan from all this time in storage.

Would I manage to get more of the dirty oil out if I let the engine run before, or if I drained it directly out of storage?

In case it matters: The motorcycle is a Kawasaki KLR 650 2008. It's a single piston engine, and the same oil circulates in the motor and the clutch (wet clutch). The first engine-start of the season will typically take some good amount of crank and choke to run.

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    If you are that concerned, just drain the very old oil out, use the cheapest 10W-30 oil you can find, fill and run on that oil for ten minutes (idle, do not ride), drain this oil out hot, and then fill with the proper Kawasaki oil or equivalent. Because you have a "wet" clutch, you may likely need specific oil for this application - not just automotive oil. – SteveRacer Jun 19 at 2:10
  • not very concerned. i’d consider “it doesn’t make a difference” a valid answer. it saves time — this time around had to wait an extra day because the battery was completely dead and motor wouldn’t turn. i was hesitating to do the change while the battery was charging. – mvm_init_js Jun 19 at 2:42
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It is my understanding that the reason you should warm engine oil prior to draining it is to save time because it increases the speed at which it will flow out of the sump. On that basis, you should be fine to drain the oil but you may want to leave the sump plug out overnight as it will take longer to drain than if it were warm.

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    By warming the engine you are changing the viscosity of the oil. The hotter the oil is the thinner it gets, not only allowing it to flow faster, but also allowing it to flow out of places that it was not able to flow out of at ambient temperature. – Salvador Martinez Jun 21 at 14:52
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    I accept that but presumably it was hot at the point it was last parked so the oil will have flowed to the sump pan when it was last parked and the only place it has to flow from is out of the sump into the catch can. If there are places in the engine that oil stays in when cold, it would presumably also stay when hot. – Steve Matthews Jul 3 at 10:26

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