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Sun Dec 14, 2025 11:21 am

Hey everyone.

I’m learning about sensors and gauges.

Regarding the oil pressure switch and adding an oil pressure gauge…. I see there are some senders threaded for M10x1.0 and some for 1/8NPT. Not as much selection with the M10x1.0 though. CIP1 says they’ve been putting 1/8NPT in to the VW case for decades, just don’t tighten it too much.

So what I’m gathering is the threads are so close it doesn’t matter. Just curious to hear opinions on that. If I add one I don’t want to ruin my case.

Also… what’s the opinion on getting a sender with the dual output for the light, vs getting a T and using the factory pressure switch as well as a sender?

Thanks!

Craig

Sun Dec 14, 2025 11:56 am

The threads are almost identical so yes, it's very common to to install a 1/8 NPt into a M10x1.0 thread.

Note that the NPT is tapered so don't "crank" it in, just until it stop and snug.

A M10x1.0 is meant to go all the way in with a crush washer to seal it.

Sun Dec 14, 2025 12:43 pm

Glenn wrote: The threads are almost identical so yes, it's very common to to install a 1/8 NPt into a M10x1.0 thread.

Note that the NPT is tapered so don't "crank" it in, just until it stop and snug.

A M10x1.0 is meant to go all the way in with a crush washer to seal it.

Ahhhh I had to google the difference between a tapered and straight thread. Now I understand. Makes complete sense now. Thank you.

Craig

Mon Dec 15, 2025 10:42 am

Quote: a sender
Don't use Teflon wrap or any pipe 'dope' sealants. An electrical connection is needed between the sender and ground. I have used a crimp on ring connector between the sensor and the case for this connection because a PO made the threaded hole too big from over tightening and I had to use tape to keep if from leaking.

Mon Dec 15, 2025 12:12 pm

runamoc wrote: Quote: a sender
Don't use Teflon wrap or any pipe 'dope' sealants. An electrical connection is needed between the sender and ground. I have used a crimp on ring connector between the sensor and the case for this connection because a PO made the threaded hole too big from over tightening and I had to use tape to keep if from leaking.

Excellent tip. I did read that the sensors/sender grounds to the case and yet you still see people using tape and sealants.

I had wondered about using a ring terminal to over come this.

Craig