Fluid dynamics: How to change your motorcycle engine oil

The oil in your engine is its lifeblood: it lubricates the moving parts and stops them wearing or destroying themselves. It helps to keep everything cool, particularly on ‘air’-cooled engines and it removes harmful deposits as well as preventing them from building up again. Changing motorcycle engine oil helps with maintenance.

Oil eventually deteriorates as a result of heat cycles as well as its intended purpose of carrying dirt and debris away from key parts of the engine, and so it needs changing regularly to make sure it can keep doing its job. But changing changing motorcycle engine oil is a straightforward process and is well within the scope of the average home mechanic.

There are different types of oil; mineral, semi-synthetic and fully synthetic. The former is derived entirely from crude oil and is well suited to lower-specification engines that don’t run at high revs. Semi-synthetic uses a mixture of mineral and synthetic oils to add a range of qualities that help offer higher performance for more complicated engines.

Fully synthetic is, as the name suggests, man-made and can be tailored to give whatever qualities are required but is the most expensive option of the three.

There are then several identifiers for the compatibility of oil for your bike. The first is the American Petroleum Institute which rates oil for performance, the ‘higher’ the letter, the better. So, for example, an oil rated API SN means it is certified for a spark-ignited engine (the S) and performance level N, which is higher than M or L.

The second rating is the Japanese Automobile Standards Organisation (JASO) rating that indicates whether an oil is suitable for a bike with a wet clutch – which runs in the same engine oil – or not. An MA rating means oil that will maintain the engine and transmission and allow the wet clutch to operate effectively.

Related: Best home motorcycle tyre changing kit

Oils also have a viscosity rating expressed by numbers and letters as part of the SAE (Society of Automotive Engineers) rating. For example, SAE 10W30 means the oil works in ambient temperatures down to -25°C (the number before the W for ‘Winter’ is the coldest working temperature) up to 30°C. Note these are ambient, not the engine, temperatures and the higher the numbers, the higher the temperatures.

You may also see 4T and 2T on the bottle – this means they are designed for four-stroke and two-stroke engines respectively.

Here’s our guide to changing motorcycle engine oil.

Step 1:

Look in your owner’s handbook or workshop manual; these should tell you the specification of oil you need and the quantity. Get yourself online and order the necessary quantity as well as the relevant replacement oil filter and a new washer for the drain plug.

Step 2:

Run the engine for a short while to warm the oil up but not get it too hot. Warming it up will help it drain so as much of the old oil comes out as possible. Place a drain tray underneath the drain plug and, having put a pair of protective gloves on (old oil is fairly unpleasant stuff), loosen the drain plug and remove it by hand.

TIP: While you are undoing it, push it in to get the threads to seal as much as possible and don’t try to remove it until you feel the last thread come loose – this will help prevent warm oil running down your arm. Leave the oil draining for now.

Step 3:

Now you need to think about how you are going to remove the old oil filter. There are two main ways to do this – with a cup-style filter wrench that fits the flats on the filter and drives from a socket handle or a strap (or chain) wrench that tightens onto the filter body as you rotate it to loosen the filter. The choice comes down to personal preference or what’s available for your bike.

Step 4:

The wrench fits over the end of the filter housing and is very easy to use – you locate it like a large socket and use a ratchet or handle to undo it until it is hand tight and you can remove it. Be careful of the oil spill as you do so and lay plenty of rags or paper towels under where it locates, particularly if it is angled downwards as you work on it.

Step 5:

A strap wrench tightens itself on as you rotate it until it grips the filter housing and begins to rotate it until you can again, remove it by hand. These can be useful if access is tight or you can’t get a wrench over the top of the filter and get a handle to it directly.

Step 6:

Once the filter is off the engine, remove it and when convenient, drain its contents into the drain pan that now contains the contents of the engine. Use some carburettor cleaner or degreaser to clean the mounting face ready for the new filter.

Step 7:

Before fitting the new filter, smear a thin layer of oil around the rubber ‘O’ ring – this will help it seal properly. If the filter is mounted directly from the bottom of the engine, you can fill it with new oil to ‘prime’ it. If it isn’t then fit it empty and it will fill when you first run the engine.

Step 8:

Fit the new filter to the threaded section where the old one was removed from. Tighten it as per the instructions in the owner’s or workshop manual – this may be a torque value or a specific process.

Step 9:

Before you refit the drain plug so you can refill the engine, have a look at it to see whether there is evidence of worrying wear – metal particles, for example. If not, give it a clean and remove the old washer, replacing it with a new one.

Step 10:

Now refit the drain plug and tighten it to the relevant torque figure, as per the owner’s or workshop manual.

Step 11:

It’s now time to refill the engine with lovely clean oil. Using a funnel – to actually get it into the engine – or a measuring jug, either apply a measured quantity, taking into account any you may have already added to the filter before fitting it or fill to a level in the sight glass or on the dipstick, depending on your bike. Make sure the bike is upright and level when checking oil levels.

Step 12:

If filling to a level, check this with the sight-glass or dipstick and fill until you are roughly halfway between the upper and lower marks. Stop, then run the engine for a moment to circulate the oil, then shut off and wait until the level has settled and check again, as per the manual. If necessary, add more to compensate for filling the filter and there you go. The job of changing motorcycle engine oil is done.

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