Oil pressure gauge question!

[Stevemarsh]

Morning! Quick question, I don’t know anything about engines so sorry for silly question, 

When I start the car up and start driving the oil psi sits around 90 and once warm, drops a litre when driving, and when I stop at lights drops down until I pull away again, 

is this correct? 

 

[Kingster]

Hopefully you meant drops a little. If it drops a litre of oil you are in trouble 

Normally oil pressure is highest when you first start the engine from cold. Cold oil is thicker (more viscous) than warm and thus makes the pressure read higher. 

As it warms up it becomes less viscous so will read lower. 

But pressure will also increase with revs. So tickover will read low and full chat will read high. 

Hope this helps explain that you are seeing fairly normal behaviour.  

[Stevemarsh]

1 minute ago, Chris King - Webmaster and Joint North East AO said:

Hopefully you meant drops a little. If it drops a litre of oil you are in trouble 

Normally oil pressure is highest when you first start the engine from cold. Cold oil is thicker (more viscous) than warm and thus makes the pressure read higher. 

As it warms up it becomes less viscous so will read lower. 

But pressure will also increase with revs. So tickover will read low and full chat will read high. 

Hope this helps explain that you are seeing fairly normal behaviour.  

Ah perfect! Yes a little!! That’s great, just wanted to understand what’s happening- and you have explained so I understand! Thanks very much 

[Dave Eastwood (Gadgetman) - Club Chairman]

^ Exactly what Chris said.

Plus, be aware that, for various reasons, not least of which that many of the aftermarket gauges used in kit cars, aren't absolutely bob-on accurate, your readings may not 100% match someone else's, with the same set up, and at identical revs.

As long as they're not hugely far apart, it's no reason to worry. The main thing to be conscious of, is consistancy; so your car at identical temperatures is always around about the same pressure at idle, or at certain rpm, under load - i.e. Driving. Again, don't panic about a few psi difference here or there. That's normal behaviour in these set ups.

Please don't just clock watch though, it's easy to start doing it, and you develop a sort of gauge-blindness, if you're not careful, where you end up so focussed on a particular gauges reading, you almost blank everything else out!

Really, all you need to be aware of, is if for a given engine temperature, the gauge suddenly starts giving a very different reading, so say, showing 90+ psi at hot idle,  or say 30 psi, at high revs, when hot.

Also, apologies if this sounds a daft statement, and is obvious, but lower pressure readings than normal, do not necessarily mean the oil is low and needs topping up! (Many have now grown up and spent (long) motoring lives without oil pressure gauges, and it always amazes me how often a gauge seems to get treated like a low oil level warning!)

[Stevemarsh]

Thank you guys