How to check if engine has been rebuilt
 

91 NA coupe. Car has 147k miles. Is in very good condition. All stock except catback. Bought the car about a year ago. Heard about the more than average burning oil & the engines eventually needing rebuilt down the road. I've changed the oil in this thing twice now. Between oil changes, I have notice absolutely NO oil consumption. Changed the oil at around 2700 miles each time. Has my engine been rebuilt? Or has just been very well kept? The block itself looks somewhat clean for an engine block & the car has ran so smooth.

the easiest way to tell is by the deviations from factory original.

if its a Mazda reman, the ones up to 97-98, had a stamp in the front rotor housing, my the "Mazda" logo, it will have something that looks like a date and a serial number. after 98, they glue a square blue tag to the front cover. sometimes there is a recycle sticker on the oil pan. they also put a red sharpie on the tension bolts.

other things to look for. Paint is number 1. the factory only painted the oil pan, and it should be a gloss black. every other part of the engine should be natural.

Mazda used a grey sealant around the oil pan, and it should be neat and tidy. if you see lots of silicon that isn't grey, or is uneven and or there is lots of it, something has been apart.

an original engine should also have an even coating of dirt/oil, and should kind of match the other stuff in the engine bay. sparkly clean engine and dirty intakes mean that something has been apart.

other things to look for are non original fasteners, Mazda uses mostly gold zinc plated JIS hardware, so its all 10,12,14,17. a silver 13mm bolt is wrong. ditto the hose clamps, Mazda used a grey spring clamp on everything except a few of the heater hoses which use a wire type. all the clamps face a certain way from the factory too.

Counterintuitively, "no" oil consumption is not necessarily a good sign...the engine is designed to burn oil and has a whole special pump set up (poorly, IMO) to draw from the pan and inject into the chambers.

My (much higher mileage) engine consumes less (@ 1 qt/3000 miles) at highway speed/long trips than in the city where consumption can get as high as 1 qt/1500 miles.

Your car would go into limp mode if there was a problem with the OMP, so you don't have to worry about that. I'd suggest that perhaps more time with the car will reveal a better picture of oil use.

If you're noticing no oil consumption I'd go out and throw some pre-mix in there ASAP.