i was at a dealer ship last night looking at a 97 jeep wrangler. first thing a noticed was an after matket oil pressure gauge under the dash. when i was driving the jeep, the factory oil pressure gauge looked like it was working. the pressure was close to the same on both. i just wondered because ive heard of the oil guages stopping when a motor or something blows. the engine compartment on this jeep was superduper clean for a car with 56,000 miles? do this sound fishy? thanks

 

I willing to say that the stock one might have broke on the previous owner. Instead of going through the pains of getting it fixed at a dealership(no warranty, cost more to fix?) or fixing the stock gauge himself (too hard?). So he/she installed a mechanical gauge him/her self. Just guessing.
And probably the reason why its working now is that the dealership probably fixed the stock gauge(not that hard to) and was too lazy to take out the mechanical gauge. Guess also.
I wouldnt worry about it though. If your are thinking of buying the thing, you should pay a mechanic to inspect it, it is worth it in the long run. That goes for any used car.
And just throwing this in, when a motor is grenaded, I dont think you are going to get much oil pressure, makes since to me.

My .02
Rick