[codwapeace]

What makes them require such a short time between oil changes?

[Red Liner]

All 4 wheelers are liquid cooled.

Most commuter 2 wheelers are not. They are air cooled.

However many liquid cooled motorcycles today boast a 7,500 to 15,000 kms oil change interval.

[ninjatalli]

Originally Posted by Red Liner

All 4 wheelers are liquid cooled.

Most commuter 2 wheelers are not. They are air cooled.

Noob question - what's the difference (and pros/cons) between a liquid cooled engine vs an air cooled engine? I am aware of the obvious difference but would appreciate a bit of more schooling on this

[Justin]

Originally Posted by Red Liner

Most commuter 2 wheelers are not. They are air cooled.

Also, most commuter 2 wheelers use mineral oil or semi-synthetic engine oil whereas all 4 wheelers use fully synthetic oil.

[landcruiser123]

Motorcycles - the oil lubricates for the rotation of the crank and the sheer stress of the gears in the gearbox. They also have wet clutches. (Most mass market motorcycles at least)

Cars - the oil only has to lubricate the rotation of the crank and the VVT systems.

Never use a car specific motor oil for a 2 wheeler unless you absolutely know what you're doing.

Originally Posted by ninjatalli

Noob question - what's the difference (and pros/cons) between a liquid cooled engine vs an air cooled engine? I am aware of the obvious difference but would appreciate a bit of more schooling on this

Well, liquid cooled engines can be tuned to produce more power as their operating temperature will be controlled at all times. Also, coolant can be used to run the heater in cars.

Disadvantages: The cost of a cooling system is high with pumps, thermostats, radiators, coolant etc.

The only reason why motorcycles are air cooled is because it is cheaper to make them that way.

[vigsom]

Originally Posted by codwapeace

What makes them require such a short time between oil changes?

The only logic here is they run at higher rpms and the oil degrades faster. The oil change interval for scooters and mobikes is typically every 4000km. The 2000km change interval is a goli used by service centers, sometimes in cahoots with oil marketeers.

EDIT : to add to what @landcruiser123 said, there is no problem in using a car motor oil on a gearless scooter, but for bikes, it is recommended to use a bike specific oil only

Originally Posted by ninjatalli

what's the difference between a liquid cooled engine vs an air cooled engine?

It is all about how much heat of combustion needs to be removed,

A smaller cc engine, e.g..scooters and mobikes upto 500cc need just air cooling and the fins on the cylinder block and head give it that extra surface area for cooling. In smaller cc engines, with the vehicle in motion, the air flow is adequate to keep the cylinder block cool.

With superbikes and multi cylinder engines, liquid cooling systems are set up again since the heat duty is more.

Yes, even a 100cc scooter can have liquid cooling but it would add up on costs, would run the engine cooler than required, and thus even impact its efficiency; absolutely unnecessary.

[KarthikK]

Nice points have been posted already by the other members.

I'd just like to add that liquid cooling is better suited to (and usually found in) high compression ratio / higher performance engines which need more efficient cooling through all kinds of situations. Air cooling is more suited to commuter segments as someone already pointed out. The engine oil undergoes faster cycles of wear and tear in air cooled engines and therefore needs to be changed out a bit more frequently. The additional machinery needed in a liquid cooled setup can offset the cost advantages of a simple air cooled setup on a commuter, and is therefore more prevalent on costlier bikes than the entry level ones.

There is also a hybrid form of the air/oil cooled engines which some bikes use today - examples being the RE 650 twins and Himalayan, etc. These primarily use air cooling but the engine oil circulated is also made to pass through a small radiator to cool it off with the outside air, and this helps with the additional cooling needed for specific (higher performance) range of operation. These generally carry a larger oil capacity than traditional air cooled bikes and they boast of lower frequency of oil changes - it is around 10,000 km or 1 year for the 650 twins. Experts can correct me if I'm wrong .

[ast.ggn]

Apart from the reasons mentioned above, I can think of one more reason. Motorcycle Service centers/ Companies trying to earn more money through frequent oil change.

Majority of motorcycles in India are commuters where cost of oil change is quite low eg: Rs. 350 for my Xpulse. Although Hero recommends change at every 6000 kms but service center changes it every 3000 kms. It doesn't hurt my pocket and at the same time dealership (company in turn) makes money. Look at the number of bikes serviced at Hero dealership in a day. For premium bikes, Suzuki and Kawasaki still have shorter service intervals. Someone please correct me if I am wrong.

PS: Even few car companies had short intervals till few years back eg. Honda, Toyota. But all of this was changed when Fiat and VW marketed their 15k service intervals and they were forced to changed their strategy.

[Vysakh]

Originally Posted by vigsom

The oil change interval for scooters and mobikes is typically every 4000km. The 2000km change interval is a goli used by service centers, sometimes in cahoots with oil marketeers.

It depends on the kind of oil too. On my 150cc, mineral oil would lose all it's viscosity by 2500km and become watery, whereas semi-synth would hold decent. Fully synthetic would last 4000km.

[Gansan]

I am not familiar with the interval for liquid cooled Motorbikes. But for typical commuter bikes it is approximately every 3000 km/3 months. With synthetic oils, this can be extended a bit. Perhaps an additional 1000 km / month.

The main reasons in my opinion are:

1) They have much smaller sumps. My Splendor takes just 900 ml of oil.

2) Air cooled engines. The cooling has to be taken care of by the oil.

3) They run at very high RPMs. Their typical low end will be higher than the red line of many cars.

4) The engine oil also doubles as transmission oil. Because the engine and gear box are a single unit.

[sagarpadaki]

One important aspect that users usually do not consider is topping up the oil. On commuter motorcycles, oil gets consumed and levels drop by 100 to 200ml after say 1000 kms. So it is important to top up to the capacity. This will also help in extending drain intervals even on mineral oil to 3000 to 3500 kms.

Only downside is to keep a spare bottle/ buy bigger cans of oil and keep inspect oil level every 1000 kms

Bajaj Pulsar engines, are notorious for engine oil consumption via the crank case ventilation route!

[AMG Power]

Cars also have had air cooled engines and the better known ones are early Porsche 911, 912, VW Beetle and Karman Ghia models. Porsche and VW have however discontinued air cooled engines.

[srini1785]

Originally Posted by AMG Power

Cars also have had air cooled engines and the better known ones are early Porsche 911, 912, VW Beetle and Karman Ghia models. Porsche and VW have however discontinued air cooled engines.

Slight addition: These were forced air cooled models with for eg a 11 blade impeller fan for Porsche 911. Air cooling in bikes are through natural air drift.

[Jeroen]

Originally Posted by srini1785

Slight addition: These were forced air cooled models with for eg a 11 blade impeller fan for Porsche 911. Air cooling in bikes are through natural air drift.

There are a few cars that have just natural air cooling. The Morgan Three wheeler springs to mind:

https://www.morgan-motor.com/3-wheeler/

The main reason for the forced air is of course, the engine is simply inside the body of the car. And in the case of the Porsche and VW at the back too.

The Morgan has the engine block facing right into the driving wind. Just like a bike. In some countries you would actually only need a bike driver license to legally drive a three wheeler.

When it comes to the original question: I don’t see the type of cooling making a huge difference perse. The biggest difference between the bike and the car when it comes to oil, as mentioned already I would think: On a bike you will often have the same oil doubling up for the clutch and transmission as well. Combine that with a relative small volume of oil to engine volume and power compared to your typical car.

Not sure if the high RPMs is a factor. It’s more down to total cilinder/piston surface that needs covering on each stroke I would think. Bigger capacity it adds up quickly as it expands to the 2nd power with the diameter of the cilinder. So a combination of RPM, stroke, boring that is relevant. Not sure how that compares bikes to cars.

So the oil on an bike needs to “work” much harder on more moving and wearing parts than in a typical car engine.

Also, but I have never checked this, just a gut feeling; Are typical bike sumps a lot smaller relative to the engine size comparing them to cars. i.e. do bikes relatively speaking have less volume of oil to start with? My little Alfa Spider, 110 BHP, 2.0L engine has 6 liter of oil!
On most modern car the volume of engine oil has come down, but still. What is the average ratio quantity of oil to engine volume/BHP on bikes?

Jeroen

[vrprabhu]

Originally Posted by Jeroen

What is the average ratio quantity of oil to engine volume/BHP on bikes?

Originally Posted by Gansan

... They have much smaller sumps. My Splendor takes just 900 ml of oil ...

The typical 100cc - 150cc bikes have oil requirements varying between 900ml to 1000 ml i.e. between 7ml - 9m per cc.

The cars (which I know of) with engines from 800cc to 1400cc have oil requirements of 3000ml - 3500ml approx. 2.5 to 4ml per cc. Less than half the proportion of bikes.

Do air cooled bikes have a higher operating temperature? (Because cooling system of cars ensure that the operating temperatures are monitored and cooled?)