So I have an S5 but the engine I got came with an S4 oil pressure sender. I am assuming they send out the same signal correct? If I find some sort of connector to go onto that goofy circle thing can I just splice that into the stock wire (the S4 has a circular connector and the S5 just has a male metal prong thing with a slip on connector)?

 

Find the FSM for the two different years and read the test methods for both. I'd bet money that they're the same, because it's just going to be a varying voltage signal.

Or do a search for installing an S5 cluster in an S4 car. If the clusters will swap, then the sending units have to be compatible.

 

The sender is the same for 81 to 92 I believe.

 

So you are saying it sends the same signal but may have slightly different connectors correct?

 

Yes

 

Mazdatrix sells the same part for 81-92...makes no mention of connector differences (if any).

 

There is a connector difference I know that for sure.