Oil Pressure Gauge Differences

That's interesting. I have not noticed that before. It also looks like the red line comes sooner on the second car at 6500 rpm - You can't see it on the first picture but I expect it is red lined at 7000 rpm which is what I normally see.
Do you know the year or serial number of the second car?

 

I noticed my oil pressure gauge responds to my headlights being on. Nice easy way to dial up more oil pressure

The oil pressure senders can go funky and in my case with the lights on it would most likely be a ground with resistance somewhere behind the dash because the light itself isn't connected to the gauge circuit.

 

Having looked in my database, it is clear that the oil pressure gauge change was made at the same time as the switch from carbs to injection.
I'm not an engineer, so have no idea why an injected engine would run at a higher oil pressure.

 

My oil pressure gauge is different to both of these. Being in Lb/0 it reads 85 at vertical, 170 at the far right.

On the tachometer, my redline is at 6500rpm.

(My car is a UK, 1979 400i).

 

As far as I know the 4.4 litre has a 7000rpm redline and the longer stroke 4.8 and 5.0 has 6500rpm redline.

 

Correct, 365 GT4 2+2 has a 7000rpm redline, and a 400/400i/412 has a 6500 rpm redline.

What prompted the oil pressure difference was probably similar to the engine differences--did the 4.8 liter cars have a bit of higher possible oil pressure--moving the max 10 bar to 12 and thus changing the scale?

 

Brian - You may be on to something. I've done several inquiries about a new oil pressure sender and they all say that my 400GT should have a 12 bar sender unit although the instrument is graded 10 bar. My oil pressure may not be on the low side after all - but instead normal given the 20% difference in scale.

 

Wow did I ever read the original post wrong lol. My wife says I need glasses, she might be right....

 

My gauges do the same as yours. The oil/water gauges all read a lot higher when I have the headlights on. It gave me cause for concern the first time I drove it of a night but I have now gotten used to it.