Oil temperature sensor for your car

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Lubricant always at optimal temperature with the oil temperature sensor

Though small, the oil temperature sensor is an important component for smooth engine operation. As its name already says, it manages the temperature of the engine's lubricant. Its data are not immediately essential for the driver, but all the more so for the control unit.

Why is the oil temperature so important?

The amount of oil and the pressure are only two crucial factors for adequate lubrication. The oil temperature influences its lubricating performance. The hotter it is, the runnier it gets. Oil being too inviscid can no longer fulfil its task. In the professional jargon this is referred to as oil film rupture. The metal-on-metal friction of the engine's moving parts speeds up their wear.

Causes for high oil temperature

The oil temperature can be influenced by two factors:

• heat from the combustion process
• friction heat in the engine

The engine overheats when it is either insufficiently cooled or running too lean. The air/fuel mix being too lean generates a hot combustion running up the engine temperature. If the engine is supplied with insufficient oil or it gets too runny, this will add to the temperature as the internal friction intensifies.

Use of the oil temperature sensor

The oil temperature sensor was very important in air-cooled cars. These had no coolant circulation and therefore the only information source on engine temperature was the oil. Nowadays, only motorbikes have an air-cooled engine. In cars the oil temperature sensor is an additional temperature meter, compared by the control unit to data from the coolant temperature sensor. If there is too much deviation between both values, the control unit issues an error message. Additionally, retrofit oil temperature sensors can be installed. They are connected to a dashboard display. For the average car this is an interesting optical feature. It is only really useful for racing or rally cars, providing the driver with additional information on the engine condition. Maintaining a careful driving style it is useful to be aware of the exact oil temperature. The oil is heated by the engine faster and more directly than the coolant. Especially in the warming-up phase the oil temperature is considerably more precise than the values from the coolant temperature sensor. A rule of thumb states that under 50° C the car should only be driven in a most considerate manner.

Installation of an oil temperature sensor

The oil temperature sensor consists of the sensor and a display. Until recently the display was a round instrument installed on the dashboard. Nowadays a very interesting alternative exists: modern oil temperature sensors have a Bluetooth connection linking up with a smartphone, making your phone to an additional instrument. This solution has the following pros and 1 con:

• + much easier to install
• + no drilling in the dashboard required
• + cheaper
• + comfortable use
• - remote hacking possible

All retrofitting solutions should always be bought as a set which is approved for the car type. The installation of the sensor makes an intervention in the engine electronics necessary. This is not so evident in modern engines. The extensive sensor system in a modern engine operates with precisely calculated data. The data of a sensor are in essence resistance values which can be changed by branching a cable. As a result the control unit receives faulty data which can lead to an error message. The oil temperature sensor is installed directly on the engine block. The products available in retail always have a detailed installation manual which should be exactly followed. Often, a blind bolt is already available on the engine block for installation of the oil temperature sensor. If this is not available, there is a very simple solution: the oil filler cap with integrated sensor makes this upgrade very easy: just renew the cap. Alternatively there is an adapter piece for which an additional hole should be drilled.

Prices for oil temperature sensors

The retrofitting kits for the oil temperature sensor are amazingly cheap. Very attractive digital display included, prices for a kit start at ca. 30 EUR(± £27). The choice ranges from classic round instruments with analogue display to small, elegant digital instruments with a large numerical display. Very interesting too are the combination instruments, with a rpm indicator and a combined water and oil temperature display.