Mazda 626 Engine Problems

BUY the RX8. Rotary engines are typically heavier on fuel than a four-cylinder engine, and your V8 comparison is probably correct. They have also been a little heavier on oil than a piston engine, but that's not a problem. The RX8 is a high-performance sports car and needs oils that protect it against hard driving.

It’s an old car and you have to expect some wear and tear over what is now coming up for 20 years. Smoke on a cold start isn’t necessarily oil related; it is often condensation and nothing of concern. The oil leak is probably just a gasket that has hardened or split and needs replacing. If it is burning oil it could be due to wear in the valve guides or it could be worn piston rings or wear in the bores. If it’s not leaking a lot, just leaving a spot on the driveway, and it’s not using much oil I wouldn’t be too worried about it. The worst-case scenario would be that engine might need reconditioning.

The first place to start is to check all the engine tune items to make sure they are all in good shape, that's plugs and leads etc. After that I'd check the crank angle sensor and its connections.