Disclosure: We may get commissions for purchases made through links in this post.
For most of us in the riding community, the question, “Is motorcycle oil the same as car oil?” may have crossed our minds at some point. It may be out of plain curiosity or due to an unforeseen predicament.
Whatever the reason, today’s article will shed light on this topic and finally detail the difference between these motor oil types.
The biggest differences between motorcycle oil and car oil are the components protected and lubricant flow inside the mill. Car oil mainly safeguards the engine. Motorcycle oil lubricates the engine, clutch, and transmission — in addition to cooling parts that rise in temperature.
Come to think of it, the only facet that appears shared between these two is their oil types. Whether or not they are interchangeable or have the same amount of workload seems inconspicuous.
Continue reading to learn more about each lubricant’s properties and characteristics.
Is Car Oil the Same as Motorcycle Oil?
Veterans and enthusiasts would know the answer to this long-standing question would all too well. But for many inexperienced motorheads and vehicle owners, it will never cease to tickle their curiosity.
Superficially, it is easy to assume that these motor oils are similar. But it is not the case at all — as you will soon find out in the succeeding sections.
Motorcycle Oil vs Car Oil Explained
Motor oil — be it for a car or motorcycle and regardless of viscosity — is the lifeblood of your engine.
This thin film of slipperiness keeps the engine, clutch, and transmission parts working smoothly without slagging each other. Likewise, it aids in cooling off heated components and sealing in combustion pressure in the system.
On the outside, there may be shared functionality and viscosity grades between motorcycle oil and car oil. But by the end of this guide, you will know just how different these two lubricants are.
Motor oils have several attributes that make them unique (if not ideal for their designated vehicle). Below is a non-exhaustive list of these properties.
Viscosity Index: the rate of a motor oil’s viscosity change due to changes in temperature; typically ranges from 95—140, depending on whether the motor oil is mineral, hydrotreated, semi-synthetic, or fully synthetic
Thermal Stability: the ability of the motor oil (or any fluid) to maintain its original properties and resist breakdown under heat stress and extended service time
Oxidation Stability: the rate of oxidation relevant to exposure to extended periods of high temperatures, water, acids, and catalysts
Pour Point: the least temperature at which motor oil can pour down from a container; the temperature at which motor oil ceases to flow.
Demulsibility: the ability of motor oil to release water, specifically when the engine is operating in humid or wet climates (a facet that has greater significance in industrial oils)
Flash Point: the lowest temperature at which motor oil will generate vapor and ignite when exposed to an ignition source like fire or an explosion
Fire Point: the lowest temperature at which motor oil (or any combustible substance) continues to burn in the air after exposure to an ignition source
High Shear Rate Viscometry: (a.k.a. HTHS) a bench test that makes use of a tapered bearing simulator or TBS to measure motor oil’s high shear rate at 100 °C (ASTM D4683) and 150 °C (ASTM D6616)
Oil Gelation: a marked increase in motor oil’s flow resistance over and beyond “the normal exponential increase of viscosity with decreasing temperature, particularly at lower shear stresses and temperatures.”
Total Base Number (TBN): a measurement of motor oil’s ability to neutralize resultant acids during engine operation
Total Acid Number (TAN): a measurement of acidity helpful in estimating the amount of “additive depletion, acidic contamination and oxidation of lubricant degradation” in motor oils
Most of these terms are determined via ASTM testing and are quite technical — hence, they will not be the gist of today’s article. Instead, we will focus on the functional disparities between two- and four-wheelers to better understand why motorcycle and car oils are specifically made as such.
Motorcycle vs Car Oil Differences
Between motorcycle and car oil, the latter’s main responsibility is safeguarding the engine (view on Amazon), while the former also protects the gearbox and clutch assembly. This makes motorcycle oils more hardworking compared to its counterpart.
Although following manufacturer recommendations apply to both, using the right motorcycle oil is a more urgent requirement, as it prevents oil disintegration and premature engine failure. In addition, motorcycle oil aids in reducing heat buildup in the cylinders, valves, and other engine components.
Oil Sump Size
The size of a motorcycle oil sump (view on Amazon) is significantly smaller than a vehicle — meaning there is less oil in a motorcycle engine than in a car engine. Hence, the composition of motorcycle oil has been done in such a way that its properties make up for its quantity.
This mechanical disparity is one of the biggest reasons motorcycle and car oils have different formulations and characteristics.
Motorcycle oil works harder in cooling off parts prone to heating up since less oil circulates throughout the power mill. The respective motor oils compensate for shortcomings in heat dissipation.
Since most automobiles are water-cooled, car oils do not need to work as hard to keep heat-prone components cool. Meanwhile, the reverse is true for motorcycle oils, as two-wheelers largely rely on air cooling (a less efficient way of dissipating heat from the engine).
The air cooling configuration in most motorbikes can become problematic, especially in stop-and-go traffic where rear-cylinder temperatures exceed 216 °C (420 °F) and airflow does little in cooling engine components.
But even with liquid-cooled motorcycles, engine parts inherently run hotter than those in four-wheelers, making them incompatible with car oil.
Between cars and motorcycles, the latter operates at significantly higher engine speeds (sometimes even reaching 20,000 RPM in some models). On the other hand, vehicles do not push their revs as high as this — meaning reduced stress on engine components.
It is vital to know this difference because higher RPM redlines come with higher loading and shearing forces (not to mention greater stress on the power mill).
Exorbitant loading and shearing forces are the no. 1 cause of viscosity loss and lubricant film breakage. Both of these outcomes lead to engine wear and oil foaming.
Putting car oil in a motorcycle will only dampen the motor oil’s lubricating properties on top of exacerbating premature engine wear.
Motorcycle oil is designed to flow smoothly through narrower passages. It requires balanced friction characteristics to handle the clutch (view on Amazon) and gearbox with the engine.
Unlike cars, motorcycles typically utilize a wet clutch that warrants a lubricant formulation meeting JASO T903 MA/MB/MA2/FA/FB/FC/FD frictional requirements.
As you would have guessed, JASO T903 is a Japan-specific motorcycle oil rating. It functions similarly to other regional organizations such as API, SAE, ILMA, and ACEA.
The significance of the JASO standard is that it pioneered the development of the grading system for motorcycles and measured “oil resistance to clutch friction or slippage” — a parameter not taken into account in defining technical requirements for car oils.
Car oil contains friction modifiers (often with detergent additives) needed for transmission efficiency and fuel economy. These additives are detrimental to motorcycle function and can potentially lead to sludge buildup on the piston crowns and valve train, slippage, and loss of acceleration when used on the latter.
Propensity for Corrosion
While both car and motorcycle oils have anti-corrosion properties, motorcycle oil is generally superior to car oils in this area. The reason being is that motorcycle riding does not happen all year round.
Riding season typically starts in March and ends in mid-November. Outside these months, motorcycles are stored inside the garage, their disuse making their components susceptible to rust and acid corrosion. As such, a motorcycle lubricant’s formulation will have to match its utility.
Car oils generally have lower viscosity, whereas motorcycle oils are formulated with higher oil viscosity. In case you are wondering, “Why do manufacturers require higher viscosity grades for motorcycles than cars?” below are the main reasons:
- For temperature and burn-off protection
- For prevention of gear failure
- For mitigation of shearing (breakdown or loss of oil viscosity)
Motorcycles have a higher power density (horsepower per cubic inch) than vehicles, alongside higher compression ratios. This power density-compression combo causes two-wheelers to operate at higher engine temperatures — hastening engine wear, viscosity loss, and chemical breakdown.
If motorcycles were to run on car oil, the latter’s composition would not be able to keep up with bike functions. Its formulation will be incompatible with the motorcycle’s operational requirements.
Additionally, viscosity loss will occur sooner than intended since car oils are unfit to simultaneously protect the clutch, gearbox, and engine. But the worst that could happen is your gearbox not getting enough lubrication, resulting in serious transmission issues in the long run.
Mixing Motorcycle and Car Oils
Both motor oils protect against friction, premature wear, deposit/sludge formation, and oxidation (to name a few). But given their differences cited above, replacing one with the other is generally ill-advised.
Filling a vehicle with motorcycle oil would adversely affect fuel economy and vehicle performance. In like manner, using car oil on a motorcycle would lead to engine damage.
So ideally, the answer to the question, “Can you use car oil in a motorcycle?” would be a no.
However, you never know when you will encounter an emergency and not have access to either type of lubricant. Mind you, this unfortunate incident could happen even to the best of us.
At this point, you have no choice but to mix different motor oil with what is already in your engine — provided the following parameters are met:
- The motor oil label is not “Energy Conserving.”
- The viscosity range of the oil matches OEM recommendations
- Your motorcycle does not have a wet clutch
- The lubricant to be used in your vehicle is a 4-stroke motorcycle oil
The last two parameters are extremely important and should ideally be met. Otherwise, do not risk using either lubricant to replace the other. Doing so will only entail huge risks that could translate into a compromised drivetrain or engine failure.
Conclusion — Motorcycle Oil vs Car Oil
In summary, motorcycle and vehicle engine oils differ in their pour point and protective properties. These two attributes (among other things) affect the longevity and effectiveness of this viscous, translucent substance.
Appearance-wise, the distinction between motorcycle and car oils is seemingly close to negligible. But if we consider functional differences and motor oil properties, the reverse would be true.
Even if both lubricants act as a friction agent and a shield against corrosion, the formulation of motorcycle oil vs car oil does not really work the same way. That said, it is best to keep a spare container in your trunk for emergency cases.