Warm or Cold, When to Drain Motorcycle Oil

Warm, not hot, and not stone cold. Warm oil is thin enough to leave the engine quickly, and it carries the fine material it picked up out with it. Hot oil scalds, and a hot exhaust burns forearms before the oil gets the chance. The other two things that decide how much old oil actually leaves are whether the bike is upright while it drains, and how long you let it drip.

Difficulty	Time	DIY cost	Tools	Safety
Beginner, with one thing to respect	About an hour, most of it waiting	$0, this is a timing decision	Drain pan, gloves, rags, a way to hold the bike upright	Hot oil, hot exhaust, bike stability, used oil on skin

The other half of this job is the plug and the washer under it. If you have ever felt a drain plug go soft as you tightened it, read drain plugs, crush washers and stripped threads first, because draining hot feeds straight into that problem.

Before you touch anything

• Hot oil does not brush off. It arrives as a stream and does not stop when you have had enough. On a bare forearm it stays where it lands and keeps giving up heat into your skin, which is the whole reason this page argues for warm rather than hot. Wear gloves that come past the cuff.

• The exhaust burns you before the oil does. The drain plug usually sits low and central, and your forearm passes close to a header pipe to reach it. Headers hold heat long after the cases have come down to something you would call warm, so the timing that makes the oil safe does not make the pipes safe. Look at the path your arm has to travel before your arm travels it.

• The bike falling. You are applying force to a fastener underneath a machine that something else is holding up, and this job also has you waiting around beside it. Use a proper stand or lift on level solid ground, never a jack alone, and stay out from under it.

• Fire. The warmer you drain, the hotter the pipes still are when the first surge comes out. Oil on a hot exhaust smokes and can ignite, so catch that surge with a rag and clean the pipes before the engine is started again.

• Used oil on your skin. The US Environmental Protection Agency describes used motor oil this way: "Used motor oil is insoluble, persistent, and can contain toxic chemicals and heavy metals." Source: US EPA, Managing, Reusing, and Recycling Used Oil. Wear eye protection and nitrile gloves, and never clean your hands with petrol or solvent. Warm oil leaves faster and splashes further than cold oil does.

• Never run an engine in an enclosed space. Warming the engine is the first half of this job, so the risk is built into the method. Warm it outdoors, or with the door fully open and the bike beside it.

What warming the oil actually changes

Oil gets thinner as it gets warmer, and that has two consequences at the drain plug. The first is speed. Cold oil clings to every internal surface and comes down slowly, warm oil runs, so in the same standing time you get more out and leave a thinner film behind.

The second is what the oil is carrying. An oil change is not really about removing oil, it is about removing what is in the oil. While the engine runs, the oil holds the fine material it has picked up in suspension. Left standing cold, some of that settles out. Drain warm and it leaves with the oil. Drain cold and a share of it stays behind, to be picked up again by the fresh oil you just paid for.

Why not hot, which is the part most guides skip

You get burned. Oil at running temperature is far above the point at which liquids scald, and unlike hot water it does not evaporate away or run off cleanly. Warm oil that flows freely will not injure you. Hot oil will, and the difference costs nothing but a wait.

Everything around the plug is hot too. Headers, cases, filter housing and filter. Draining hot means working fast around things you cannot touch, which is how a plug ends up in a pan of scalding oil.

The plug goes back into metal that is about to change size. On a great many motorcycles the drain plug is steel and the case it threads into is aluminium, and aluminium expands and contracts about twice as much as steel for the same change in temperature. Torque set on a hot engine is not the clamp you have when it cools, because the aluminium case contracts more than the steel plug and the joint relaxes. That is how a plug torqued hot weeps cold, and how the owner ends up nipping it up into a thread that will not survive it. Fit the plug once things have come back down and torque it once, to your model’s figure.

What warm means, without a thermometer

Run the engine until it has clearly come off cold, then shut it off and walk away for a while. Two useful things happen in that wait. Oil that was up in the cylinder head and around the cases drains back into the sump, which is oil you would otherwise leave behind, and the exhaust stops being an immediate burn hazard.

You are aiming for cases that feel warm to the back of a bare hand held near them, without you flinching away. If you cannot bring a hand close to the plug area it is still too hot, and you lose nothing by waiting. How long that takes depends on the bike, since an air cooled engine sheds heat far faster than a liquid cooled one. Go by your hand, not by a clock.

Why the bike being level changes how much comes out

The sump is a shaped cavity and the drain plug is a hole at one point in it. Oil pools at whatever the lowest point of that cavity happens to be. Stand the bike upright and the lowest point is the one the engine designers intended, normally at or near the plug. Lean the machine on its sidestand and the cavity tips with it, the pool moves to the low side, and the plug may now sit above part of the oil you are trying to remove.

Which direction helps and which hurts depends on where the plug sits relative to the lean on your engine, and that varies between models. So the useful rule is not lean it left or lean it right. It is hold it upright, on a centre stand, a paddock stand or lift, or with a second person steadying it vertical. The same applies when you read the level afterwards, and reading a level on a leaning bike is the usual reason a careful person overfills an engine.

Why a long drain beats a fast one

Oil leaves in two phases. The stream is most of the volume and is over quickly. The drip is the film clinging to every internal surface finding its way back to the sump, and that is where a thorough oil change differs from a hurried one.

• Take the filler cap off. A crankcase draining through a small hole with everything else sealed is draining against its own vacuum. Open the filler and air comes in as oil goes out.

• Then leave it alone. Deal with the filter, get the old oil into its container, and come back when the flow has gone from a stream to occasional drips. Past that point the returns fall away sharply.

• Rock it gently, if you can do it safely. Tipping the machine upright and back, properly supported, moves oil pooled where the plug cannot reach it.

• Do not blow compressed air into the crankcase. You drive whatever is on the outside of the case into the inside of it.

• Do not crank the engine to pump the last of it out. That runs bearings and a cam with no oil supply.

Specifications you need to look up for your bike

Value	Why you need it	Where to find it
Oil grade and the specification your maker calls for	Choosing what you refill with	Owner's manual
Oil capacity, with and without a filter change	Knowing how much goes back in	Owner's manual
Drain plug torque	Fitting the plug without stripping the case	Factory service manual
Sealing washer size, type and part number	The washer is a consumable, replaced every time	Parts fiche or dealer
The position and engine state your oil level is checked in	Reading the level instead of overfilling	Owner's manual
Filter part number and fitting instructions	Fitting the right filter the right way	Owner's manual and factory service manual
Whether your engine has a sump screen or strainer	Some designs expect it serviced at an oil change	Factory service manual

When to stop and take it to a shop

• The drain plug will not move, or its head is rounding as you lean on it.

• The plug turns with a gritty feel and then spins without pulling up tight. That is a thread failure, not an oil change.

• The drained oil carries metal flake or glitter, or looks milky. That is a finding about your engine.

• You cannot hold the bike securely upright for the drain and the refill.

• You cannot find a torque figure for your model. Get it before you fit the plug, not after.

Related checks

• How to change motorcycle oil, and which procedure your bike needs

• The drain plug oil change, step by step

• Drain plugs, crush washers and stripped threads

• What to do with used motorcycle oil

Frequently asked questions

Can I change the oil completely cold?

Yes, and it beats not changing it. You get less out and leave more of the suspended material behind, because cold oil is thicker and has had time to drop some of what it was carrying. Give it considerably longer to finish dripping.

How long should I let the engine cool before draining?

Long enough that you can hold the back of a bare hand near the drain plug area without pulling away, and no longer than it takes the machine to go cold. There is no single figure, because air cooled and liquid cooled engines lose heat at very different rates.

Does draining warm really get more of the old oil out?

Yes, for two reasons that are easy to confuse. Warm oil is thinner, so more of it leaves in the time you give it. And warm oil is still holding the fine material it picked up while circulating.

Should I lean the bike over to get the last of it out?

Not as a habit, and not on a sidestand. Whether leaning moves oil towards the plug or away from it depends on where the plug sits on your engine, so the trick that helps one machine loses you oil on another. Upright is the position the sump was designed around.

Should I run the engine before checking the level on the fresh oil?

Your owner's manual states which condition your model is checked in, and engines differ enough that it is worth following exactly. What holds generally is that the first job after a refill is to check the plug and the filter for leaks.

About this guide

Published by MotoGearRater. Universal procedure only, with no model-specific specifications. This guide has not been reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.