Engine Oil Temperature Gauge

The engine oil temperature gauge monitors and displays an important engine operating parameter: engine oil temperature. There are…

Example of a mechanical oil temperature gauge

Engine oil temperature gauges are available in several configurations. Like other automotive gauges, the engine oil temperature gauge is available in both mechanical and electrical styles. Also the engine oil temperature gauge is available in both digital and analog display formats.

Mechanical engine oil temperature gauge

A mechanical engine oil temperature gauge typically has a Bourdon tube. The Bourdon tube is then installed into the engine oil temperature sensing port. Sometimes the mechanical engine oil temperature gauge is filled with mineral oil to help the gauge resist vibration and to ensure smooth gauge movement.

Electrical engine oil temperature gauge

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Example of digital oil temperature gauge

An electrical engine oil temperature gauge has a temperature sensor which installs into the sensing port. The sensor is typically a thermistor. The resistance of the thermistor varies depending on the temperature of the fluid to which it is exposed. The electrical engine oil temperature gauge then uses this resistance value to display the corresponding temperature.

Electrical engine oil temperature gauges are typically available in short sweep and full sweep formats. The full sweep electrical engine oil temperature gauge is typically more expensive than the short sweep version. The full sweep electrical engine oil temperature gauge typically utilizes a stepper motor which requires additional circuitry to drive, thus increasing the cost,

How to choose between a mechanical engine oil temperature gauge and an electrical engine oil temperature gauge

The electrical engine oil temperature gauge is typically easier to install than the mechanical version. On the mechanical engine oil temperature gauge, the Bourdon tube can be difficult to route around sharp bends. Moreover, if the tube is too short, it is not easily linked in. Alternatively, if the tube is too long, the excess tube must be coiled.

The electrical engine oil temperature gauge is typically easier to install than the mechanical version. The wiring is much easier to route around sharp bends and to cut to the necessary length. However, the electrical version obviously requires electricity to operate, so it is not a good choice for race or modified vehicles that have limited or no electrical power available.

Both electrical and mechanical engine oil temperature gauges will typically have a back light. So, even the mechanical engine oil temperature gauge can require some electrical wiring to be performed.

How to install an engine oil temperature gauge

The gauge manufacturers instructions will show how to install that particular gauge. In general, the installation consists of seven steps.

1. Ffirst, determine where the gauge will be mounted.
2. Next, determine where the engine oil temperature sensor will be installed. The sensor needs to be in the flow of oil in order to give an accurate engine oil temperature reading.
3. Then, determine the routing for the wiring or Bourdon tube between the sensing point and the gauge. Typically, the wiring or Bourdon tube will need to pass through the firewall. Often, unused plugged ports exist in the firewall. If one of these ports is available it often makes an easy routing point. Sometimes, a new hole must be drilled in the firewall. Caution must be used when drilling a hole in the firewall to avoid damaging surrounding wires or other components.
4. Now, for mechanical engine oil temperature gauges make sure the Bourdon tube is long enough to reach between the gauge and sensing point, and also that there are no extremely sharp bends for the Bourdon tube to make.
5. Next, the wiring or Bourdon tube may be run between the sensing point and the gauge.
6. Most gauges come with 1/8 inch NPT type fittings on the sensor. Some gauges include adapters for other thread sizes and page such as BPST or metric. Care must be exercised in selecting the correct adapter as some sizes are very similar and may start a thread in but after a few turns will bind or hangup and if force the threads will be damaged and not form a leaktight seal. Many thread types require some sort of thread sealant such as Teflon tape to be used.
7. Now for electrical gauges to the ground and positive power supply may be routed typically the positive power supply is connected to a circuit that is activated only when the ignition key is in accessory or run positions to avoid draining the battery unnecessarily. For both electrical and mechanical gauges if desired the backlight may be connected. Typically, the backlight is connected to the parking light circuit.

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