New MK3 2.0i owner here. Does anyone elses oil temperature needle move around when the engine revs or is under load such as pulling out the clutch and setting off in first gear? I was testing the car last night after changing the front brakes and noticed that the needle moves around a lot. This is odd as its a temperature needle and the car had barely been running more than a couple of minutes.Â
Its getting an oil change tonight but thought I would check with other owners as to what is normal when it comes to this gauge.Â
Hiya, it’s actually a fake oil pressure gauge rather than an oil temp gauge. As revs increase / decrease so does the needle, imitating an proper oil pressure gauge. It is an “indication” that you have oil floating round the system I suppose  good that you’re changing the oil too, keep a check on the oil level, have a search on Google as if it gets low and you don’t top up to full level, or even slightly higher on the dipstick, you could suffer terminal engine damage. Weekly checks will do no harmÂ
The Mk3 has an Oil Pressure guage and a Coolant Temperature guage.
Both do not give a direct reading of the values concerned.
Stop taking any notice of them, they are part of the incar entertainment system, the coolant temperature guage does not give warning of a cracked coolant tank until the cylinder head is warped.
Check the neck of the coolant expansion tank for any cracks and replace if that is the case.
I assume that you mean the gauge top centre of dash. This is an indication of oil pressure. However doesn’t actually measure oil pressure but is a signal from the ECU as to what oil pressure should be. As you say it jumps from low to high in about 2 steps as the revs increase.
Do not rely on this gauge at all but regularly check the oil level is on the max mark on the dipstick.
As you are changing the oil check the level carefully as it can be difficult to read with clean oil. You may want to lift the rear of the car and check to see if there is any rust before it gets dark
I knew about the pressure gauge being a big con but I did not know about the coolant temp gauge also making stuff up too. How the hell are we supposed to keep an eye on these things if something as fundamental as a temp gauge can’t be resulted upon?
We’re fitting an oil pressure and temperature gauge to our NC, primarily to keep tabs on them while we’re on track days.
Oil temp will take readings from a sensor in a sump plug which has a 1/8 NPT tap in it. Oil pressure will be taken via a filter plate tap. The filter plate also has connections for the oil cooler, which is proving fun to fit.
We’re also fitting a water temp gauge which will use a sensor in the top hose.
It may seem a bit OTT but as the engine has done 97,000 miles, we figure more info is better than the laughable gauges provided as standard.
Thanks all, really interesting responses. I was not expecting it to be fake… but glad it is not symptomatic of something seriously wrong.
I changed the oil and good job too as it was overdue by the looks of the colour. Its good to see the oil filter has been made more accessible than on the old NA and NB cars! It was a much less frustrating process. The only criticism is the dipstick did not show any readings until right at the end when the last 0.5L of oil or so was added.
As for rust its an MX5! They all rust haha. Event his NC has a a lot of surface corrosion underneath.
The car is in for its first MOT tomorrow after 3 years off the road… so fingers crossed.
The filter is still a pain to get to, especially if the last person changing the oil screwed the filter too tightly. Mine come off pretty easy now, I’ve still got a 3 claw wrench as a standby.
So glad I found this. Did my first longish trip the other day and was watching what I thought was the oil temp gauge reading 75% thinking omg something wrong! Now I know! Cheers for the info.