Most contemporary cars have an orange oil pressure warning light to let you know if you are losing oil. But by the time it comes on it is probably too late and the damage is done. Many superior cars were fitted with an oil pressure gauge so that the driver could see what was truly happening. Some classics had both a gauge and an oil pressure just to make sure. Our Austin Healey had just the gauge but after an incident in 2009 I decided to fit a warning light as well.
Modern drivers aren't truly in operate of their cars and know very minuscule about what is happening under the bonnet. You have a temperature gauge so you can see if the car is over heating, other than that all things else is computer controlled with warning lights to let you know if the motor management or Abs fails, or if the oil level is low, or worse if you lose pressure. Most drivers are used to being ensconced in a quiet, comfortable car, listening to loud music and fully ignoring what the car is doing, unless it tells them there is a problem.
This was not the case on superior cars which had gauges to show either the main systems were all working. A temperature gauge and fuel gauge of policy but many of them were also fitted with rev counters and ammeters or battery gauges so the driver would know if the dynamo or alternator is charging properly. Many of them have an oil pressure gauge so the driver can monitor the oil pressure. The key word here is monitor.
Most engines run with oil pressures of whatever from 40 to 100 pounds per quadrilateral inch (psi). When an motor starts up the oil is cold and thick and the pressure will be high - maybe near the 100 psi mark. As the motor warms up, the oil thins out a bit and should determine down to around 40 to 60 psi depending on the engine. Oil pressure warning lamps tend to be set at about 5 to 10 psi, so if the light comes on you have virtually no oil pressure left and a major problem.
Most of our fleet of superior hire cars have pressure gauges fitted as approved and we do explain their function to the drivers when we take them out for a test drive at the start of their day's hire. On the rare occasions I have forgotten to mention this we have occasionally received a phone call later in the day when they have spotted that the pressure was lower than when they set off.
We had a singular situation organize on our Austin Healey 3000 while 2009. This is fitted with an oil pressure gauge but no warning light. To allow customers of all shapes and sizes to hire the car, we replaced the original 16" diameter steering wheel with a 14" diameter wheel. This gives the driver more room to enter and exit the cars and it doesn't rub on the tops of their legs.
However with the original steering wheel fitted, all the gauges along with oil pressure were graphic inside the rim of the steering wheel. The 14" wheel meant that the oil pressure gauge was now obscured by the rim and the driver's left hand. When moving, the drivers would have to make a deliberate movement to see the gauge and this assumes they remember they ought to check it, when contemporary cars don't have such devices.
Our Healey advanced a minuscule oil leak from one of the motor oil seals, as superior cars tend to. Not ordinarily a qoute as I check the levels every time the car goes out on hire. Oil leaks by their nature tend to get worse rather than fix themselves so one day on checking the car over after it had been out on hire for a combine of days, I noticed that there was virtually no oil in it and when cornering the oil pressure would drop only to recover on the straight. This happens because the oil surges away from the pump pickup in the sump as the car turns one way, and flows back when it straightens up or turns the other way.
Many years ago in my youth I had a Triumph Spitfire with an oil leak. Being a lazy youngster I waited until the oil pressure gauge moved when going round a roundabout and treated this as a signal to top up the oil level. While that may have been approved on a Spitfire worth a few hundred pounds it is not a sensible advent on an Austin Healey worth over £20,000, particularly when the customer probably won't observation the gauge anyway.
I had the oil seal replaced by my usual garage but asked them to add an oil pressure warning light as well. This is an easy sufficient procedure. The oil pressure gauge sensor screws into the motor block. This is removed and replace with a threaded brass T piece. The oil pressure gauge sensor is then fitted into one side of the T and the pressure sensor for the warning lamp fitted to the other side of the T. The institution is that oil warning lamps are orange so an orange light was fitted in the centre of the dashboard, next to the indicator warning light and wired to the sensor.
Now when the ignition is turned on, the oil lamp illuminates and goes off as soon as the motor is running. The oil pressure gauge still works as normal but even if it can't be seen behind the driver's left hand, he will know if there is a qoute when he gets an orange light right between the eyes.
Fitting an Oil Pressure Warning Light to a classic Austin Healey 3000