Initially, when CVT cars started to appear on our new and used car market, many owners had confusion about the transmission. There were numerous stories of CVT car owners using normal hydraulic gear oil for conventional auto cars in their CVT cars. And that would leave to expensive repair bills later. Honda City Vario was one of the first cars with CVT box that was sold in large number in our car market.
In one of my previous articles, I mentioned about a friend of mine who said that even though Vario is CVT, its gear oil dipstick says ATF on it. To confirm it, I asked another friend of mine who also owns a City Vario, and fellow blogger Khurram, to take photos of the dipstick and send them to me. And guess what? It does say ATF. I read around different forums that initially Honda believed a standard ATF is fine for their CVT cars until they started to blow up. That’s when Honda brought out their blend of oil for their CVT gearboxes.
Traditional automatic gearbox
Well, the thing is, both transmissions, although auto, work in different ways. Conventional auto has a torque converter, and the gear oil is pushed around inside the converter to create a cycle that then transfers rotational energy to planetary gears to drive the car, and they shift according to the speed and load. You have a turbine, a pump and a stator in your traditional auto gearbox. The pump, sometimes called impellor, rotates with the engine speed and throws the ATF outwards. The turbine catches the fluid and throws it back to the pump after reversing the direction of the fluid. And then comes the stator. It lies in between the turbine and the pump/impeller. Since turbine has changed the direction of the fluid throw, the stator directs the fluid back into the pump. And this creates a cycle. The change in the direction of the fluid is basically what makes your car move. The turbine is connected to the transmission, and that is what drives the wheels of your vehicle. It is arguably one of the most complicated mechanical systems in your car. There are loads of animation on the internet. If you are interested in the workings of the system, do check them out.
Whereas CVT system relies on pulleys and belt. CVT stands for continuously variable transmission. There are no physical gears/cogs inside the CVT like planetary gears in the ordinary auto gearbox. The purpose behind CVT is to make the shifting seamless. It is a two pulley system, a drive pulley and a driven pulley. Power comes from torque converter, and the pulleys change their girth and ratios according to the throttle position, engine rpm and load to increase or decrease the rotational output to the wheels. The good thing about CVT is that the car is always in optimal driving range. And that means ideal fuel economy. Since it is always adjusting according to engine rpm, it is sort of always in perfect operating range. Like conventional auto gearbox, CVT does not go out for gear hunting. And you will not feel the car engaging or disengaging a gear in order to find the right combination like it happens in ordinary 4 or 5-speed autos.
The bottom line is, both transmission work on different principles and geometrically, both are altogether different units. One is a big fluid pump; other lacks physical gears. Therefore, their requirements for lubrication are also different. It is best to check the user manual of your car before replacing any sort of oils in your vehicles. Always follow the directions so that your car parts don’t die on you prematurely. Happy motoring.