Oil pressure reading

Borrowed my daughters mx5 yesterday and it was a hot day and I gave it a caning to try and identify a mysterious sound- this turned out to be a wind noise emanating from the new hard top she has bought - during my experimentation I noticed that the oil pressure gauge never altered it’s position. Just above halfway. Didn’t rise when the rev limiter was touched or fall at tickover. Is this normal? Do the gauges malfunction? Thanks, john.

You don’t say how old the car is, but assuming that it’s a later model NA or an NB then it’s perfectly normal. The gauge is simply attached to a switch so it either reads or it doesn’t. The failing is if the circuit goes open the gauge reads constantly while the ignition is on. Make sure to regularly check the the gauge reads zero with the ignition on and the engine off.

Post-1995 cars have a dummy gauge; effectively like an oil pressure light.

Car is 2002. It should not act as a pressure gauge then?

No, 2002 gauge is a pressure/no pressure indicator only.

Thanks for that it explains a lot. Seems a bit daft to fit a gauge when an idiot light would perform the same task? Could have had a much more useful volt meter fitted there.

But a gauge is “cooler” than a light and suits the car better :wink:

The NC gauge (2005 cars onwards) is a moving gauge but its position is set according to engine temperature and engine revs, again, no link to actual oil pressure. As long as the engine has oil pressure the gauge will read.

Has anyone simply substituted an actual oil pressure gauge? Is there a sender on the block?

The sender is just a switch so you’ll need a proper sender then you’ll need to do some clever reworking of the gauge. I’ve seen NA gauges changed to moving types but not sure if anyone’s done it on an NB.


Thanks for the link, it’s fairly comprehensive. I think I will leave the gauge be though as my daughter probably wouldn’t know how to interpret its significance anyway. I tell her when the red oil. Light comes on stop the engine and phone me…

There is no red oil light, only the gauge.

There is this:


how bizarre is it to not fit an idiot light? proper odd that.

It is mainly down to the sender unit, you can get and fit a track dog sender unit and just reset the OE gauge needle, it will work a little slower /dampered than the OE gauge that works, but it will be working correct to tell you the Oil pressure, and just to throw a spanner in the works , do not trust the OE water temp gauge as that is dampered and NOT giving you a true reading which is the case from 1989 to 2005, a aftermarket gauge is cheap and easy to fit to see what is going on correct in there…