The oem water temp gauge is a POS! very inaccurate readings,

when you have 3 bars, it has a range from xx tot xx degrees so it's more an indication and NO gauge. If you buy an water temp gauge you see exactly what i'm talking about.

as an example, when you drive a few blocks, you see 3 bars, you drive an hour on the highway, you still see 3 bars, even at auto-x you will see the 3 bars max.

Here's the difference, when you get an water temp gauge, and you drive around, there's the point you get 3 bars on the cluster, and when you check the actual temp on the water temp gauge you notice it keeps increasing while you are driving, and is responding on normal driving, hard driving.. while the stock cluster always will show 3 bars.

and when on auto-x you see the temp rising alot and the gauge cluster is still showing 3 bars :S

But i agree, oil temp and pressure are a very good upgrade!

 

I actually wrote up a DIY for installing a SPA Design dual-display oil temperature and pressure gauge in a single pod a-pillar from ScienceOfSpeed. NVMY4N's got that doc right now, and should be posting that sometime (with pics); but it goes through the whole process of installing sensors, mounting the gauge, etc.



So far as the water temp goes, I've installed Modifry's ECT for the stock ECU. I've modified the temperature settings so that 2 bars is "ok to vtec" all the way through normal operating temperature. If I sit at a light for more than half a minute though, 3 bars kicks on, even in cold weather. If I'm autocrossing on a hot summer day, I'll even get 4 bars. On an AP1, I find Modifry's product really damn helpful, especially coupled with the oil temperature gauge.

So I'd have to throw my vote down for just the oil temperature and pressure gauges.