Can I use car oil in a motorcycle?

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Believe it or not, Facebook does have some uses. Questions of whether you can use car oil in a motorcycle engine were asked inside a Facebook group I’m in. It starts the endless tirades of Facebook experts giving answers from “It’ll be fine, it’s only a drop” to “No.”. Brilliant.

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Unfortunately, not all oils are created the same. You wouldn’t fry bacon off in ATF oil, as you wouldn’t pour litres of olive oil into the filler. Despite all being oils, they have different chemical makeups, thicknesses and properties.

Why do I need engine oil?

Oil has been used as a lubricant for a long time. First used by the ancient Greeks and Romans who lathered themselves up with Olive oil as a sexual aid. Aside from that, oils assisted the movement of large stones and other heavy objects, and animal fats were used to grease chariot axles. Animal and plant-based oils made up all lubricants until 1859 when the first oil well was successfully drilled.

motorcycle oil change
probably THE most simple job on a motorcycle!

Since then, lubricants have been successfully developed from raw oil, with various stages of refining and additives. These additives can do many jobs, including prolonging lubricant life, further reducing friction, or allowing the lubricant to cling better.

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Can I use car oil in a motorcycle?

Inside an engine, a lubricant has many uses. Oil reduces friction, but also, the oil can act as cooling, wicking away heat. With motorcycles, it gets tricky. Car oil has additives inside, aiming to reduce the friction to the lowest amount possible. This reduces wear and improves MPG figures. Most motorcycles use a wet clutch system, where the engine oil is used to cool the clutch. Not only does it cool the clutch, but oil plays a big part in the feel of the clutch and how successfully it works.

using the wrong oil
using the wrong oil can get expensive!

Using the wrong oil can cause too much slip on the clutch plates, sacrificing power transmission. Car engine oil is packed full of anti-friction additives, which will cause a motorcycle clutch to slip. If the clutch and engine used separate supplies, it would be different, but unfortunately, they are the same system, so a dedicated motorcycle oil must be used.

Synthetic or Mineral oil, which is better?

Once again, not all oils are created equal. Sometimes it can even go as far as to use different grades and types at different intervals or purposes. It’s just so confusing! One engine can recommend one oil for running the engine, and then another oil for afterwards once run in. The age-old argument of synthetic vs mineral oils still rages, and even the middle ground of semi-synthetic lingers.

synthetic vs mineral oil
synthetic vs mineral oil – Indian motorcycle

Synthetic oils are you can imagine, are man-made. This ensures consistency, quality and purity, free from any natural contaminants or bad stuff. Mineral oils are natural, from the ground, refined but can still contain trace elements of contamination.

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Despite this possible contamination, sometimes, the base of synthetic formula oils is actually mineral oil. This isn’t normally an issue as making synthetic oils can be thorough and time-consuming, taking the care and time to eliminate the contaminants.

Is mineral oil worth it?

Quite often, mineral oils are cheaper than synthetic counterparts, maybe up to a third of the price of synthetic oil. Most bike manufacturers will ship brand new bikes with mineral oil (no, they are not being cheap). One benefit of mineral oil is that it can help run an engine. Having fewer additives than synthetic oil, mineral oils can help the rings bed into the bores and gently wear in other surfaces during the run-in. The mineral oil can also catch any smaller particles of metal, which may come off components better than a synthetic. After the run in this can be swapped for synthetic oil.

motorcycle oil top up
make sure you fill with the right amount!

Should I change my oil as per manufacturer recomendations?

Of course, you should stick to the manufacturer guidelines for road bikes. Normally these give a certain mileage, usually around 8 to 15 thousand miles, OR twelve months in time, whichever is soonest. If you have a track bike, service intervals will be a lot sooner; some say it’s good practice every two or three track days. Naturally, this depends on how many sessions or hours you are out on track and how hard you are pushing.

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Do I have to use manufacturer recomended oils?

Whilst some bike manufacturers have technical partners to provide parts, the same happens with oils too. Yamalube provide Yamaha, Ecstar provide for Suzuki, and Honda even have their own oil line, but as long as the specification meets the manufacturer, the brand is a personal choice.

Why does engine oil go black?

It goes in clear and coloured, (gold, red or even green if you’re using Motul 300V), but soon enough, it goes black or at least a lot darker. This isn’t necessarily bad; it proves that the cleaning agents inside the oil are working, cleaning the engine. The whole purpose of the oil is to carry this debris and contaminants through to the filter, where it is hopefully filtered out and stored. This is the main reason changing the filter is important too!

These contaminants carried by the oil can range from tiny metallic particles worn from the engine to heat affected parts of the oil that have been up against hot components and gone hard to clutch friction material from the clutch baths. Some additives will react to heat better than others, and of course, the engines heat cycles will darken the oil as it ‘cooks’.

How do I know what oil I need?

Oil specifications will be listed inside the owners manual, as will the quantity needed for an oil change. Sometimes the intended market will need a different oil grade; for example, an Asian market where summer temperatures are hotter will require a different oil to a cooler country. It’s definitely worth checking. Should a warranty claim be made and the wrong oil used, it could get turned down, leaving you liable.

Personally, I have always used Castrol’s oil checker tool, it is good for telling you the grade needed and the quantity needed for a service.

Oil is graded with two numbers separated by a ‘W’, for example, 10W40 or 15w30. These two numbers give two different viscosities, one (the first) at a low ambient temperature and the second at a high ambient temperature. The higher the numbers, the thicker the oil at those temperatures.

oil grade chart
oil grades and temerature ranges

How do I check my bikes oil level?

Most bikes will have an oil sight glass, giving a minumum and maximum mark. Most manufacturers will insist on checking the oil whilst hot, so get the engine up to temperature, and lean the bike up straight and look where the oil level is. This can be tricky if you are on your own, you can either use a paddock stand, or I have a thick old wooden chopping board which goes under the side stand. If you have an acomplice, either they can hold the bike and you check, which makes it much easier.

motorcycle oil level check
the two score lines give min and maximum

Does a thinner oil give power?

Using a none specification oil can cause damage to the engine. Tolerances within the engine, particularly on bearings, might not get enough oil to reduce the friction, even reducing power. Oil pumps might not pump the wrong oil, which can lead to catastrophic failure and severe damage. Race oil designed for race engines will also not work well in a bike with looser tolerances like a road bike. Road bikes are also subject to conditions race engines won’t experience, like long times at idle and rapid temperature changes, as speed changes frequently.

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