Autometer Oil Pressure Users...Question

[seraphiem]

I installed an electrical 90° Sweep gauge. Yeah I know I should have went mechnical. Figured it would augment the idiot light as a rough indicator.

First off...how non-linear/linear is this thing? At hot idle its barely sitting above the 0 PSI mark.

And do they give precise results?

I've witnessed my gauge readings vary from dead center between say 37.5 for 3k rpms and then later 25 PSI for 3k rpms. Temps and conditions are almost always the same.

Note: Rod bearings were replaced about 1k miles ago as a preventative. I run 5W-30.

 

[NotSoSlowSHO]

I've witnessed my gauge readings vary from dead center between say 37.5 for 3k rpms and then later 25 PSI for 3k rpms. Temps and conditions are almost always the same.

Something is up. Your oil pressure readings when hot at 3k rpms should be near 50PSI.

What are your cold start idle readings? You should have 50-60 PSI at cold idle.

And yes, the gauges are inacurate at the low end of the gauge.

 

[seraphiem]

At cold start it'll read over 50. 75 PSI when cold and at 3k.

I thought the guide was 12.5 - 10 psi per 1k rpms. So I'd assumingly be good if I'm truly at 37.5 PSI like my gauge sometimes indicates.

I think I answered my own question but I think I need to check my sender lead and then properly ground it.

 

[Off Road SHO]

Did you use the AutoMeter sender, or the stock Ford unit? You have to use the AutoMeter sender to get accuracy and the correct scale. I use AutoMeter Electrics in the Other Woman and they are very accurate.

Tom

 

[F-22 Raptor SHO]

At cold start it'll read over 50. 75 PSI when cold and at 3k.

I thought the guide was 12.5 - 10 psi per 1k rpms. So I'd assumingly be good if I'm truly at 37.5 PSI like my gauge sometimes indicates.

I think I answered my own question but I think I need to check my sender lead and then properly ground it.

Oil pressure can vary depending on type of oil (10w or 5w), temperature, how long your car is at that temperature, and of course rpm. At cold startup my 5w30 is at 70 psi....80 to 85 psi when I drive. until the car warms up and stays warm for more than 15 minutes in this cold weather. At that point I get 10 to 12 psi per 1000 rpms.

I never read zero psi with my mechanical gauge.

 

[seraphiem]

Ok,

I put a dedicated ground lead on the Autometer sender that I'm using. Its teed off the block so I still have the stock 5 ~ 6 psi switch.

I still have found the same gauge behavior but noticed way it varies. I'm just an idiot.

When the engine is first hot (ie water temp is good and the idle oil pressure drops to around 10 ~ 12) I'm seeing great numbers and am approaching 50 psi at 3k.

After city driving (lots of stop and big on the go) for quite a while I'm still reading the same water temps but I notice roughly 30 psi at 3k rpms.

Yet after some long steady hwy driving I'll read close to 50 psi at 3k rpms again.

Guess I didn't take into account oil temp and heatsoak. Guess I need to stop worrying.

I swear I'm more Obsessive Compulsive with my SHOs then anything else I've ever owned.

Thanks All

 

[NotSoSlowSHO]

With 5W oil, you will see reduced PSI readings in stop and go traffic. Oil temps vary quite a bit, even more so than coolant temps during stop and go driving.

My 10W, even with the car near the radiator fan kick-on temp (mine is set to 205), my oil PSI readings are always above 45 PSI at 3k. When temps drop on the highway (185 T-stat), oil PSI readings are a touch above 50 PSI at 3k.

It makes complete sense that the PSI readings go back up after extended highway driving.

And yes, worry a bit less, and drive a lot more