Oil pressure is jumping from 20lbs to 0lbs,truck almost dies then the oil pressure jumps back up to 30lbs then back to 10lbs ,

Sounds like you have a wiring problem, check the plug connector and wiring that plugs into the ignition switch, look for discoloration or signs of over heating or melting, if ok , unplug the connector from the ignition switch and with 2 jumper wires you can hot wire you car, and test if it stays running, jump the hot wire to the coil wire, and jump the hot wire from the starter to ground until it starts up.

cold oil is thicker, higher rpm=more pressure .factory guage is actually working like it should. if worried hook external guage on oil galley plug and check oil press.manually.

Sounds to me that it has jumped it timeing. This will make you not have any oil pressure and will also make it back fire. You will need to replace the timeing chain and inspect the gears to see if they are worn. And if the show signs of wear change them. You only want to do this onec.

Sounds like you had better check your oil level before you have a knocking noise. If oil level is ok, change your oil pressure sender.

remove timing belt check lower crank sprocket the key way may have stripped also check camshaft and idler bearing timing should never jump especially back

hope this gives you some ideals plz vote comment reply if you need more help

What does *** mean??? If they dont cover it, call MAZDA and go above there heads.

disconnedt the fuel line from the rail and check the pressure from there, if good go to the pressure regulator

I had the same problem with mine. I installed a fuel pressure gauge, and drove around until the problem started. The truck should be running between 48 to 56 lbs. of fuel pressure. Mine ran at idle at 42lbs. , not even high enough. Drove it for about 20 minutes, and it started to stumble. Fuel pressure dropped to 30lbs, 20 lbs - then all the way down to 2lbs. I shut it off, and it would not start back up. 30 seconds later, I turned the key and it came up to 10lbs. press. 10 more seconds 20lbs. After almost a minute, it came up to 42 lbs. started and I drove away. I replaced the fuel pump assemb. on 7/3/2008. Drove it around,and the problem is gone. Mine is a flex fuel, and the pump retails for $668.00. I did find a AC Delco pump for $221.00. I hope this helps.

The low number bothers me...some people will tell you that 10lbs is fine, however this engine generally runs at least 30 at idle hot, sometimes a bit lower but not much.Pressure drop hot is because the oil flows easier when warm, and internal clearances change as well. First, I would have the pressure verified by using a mechanical gauge (yours is electric) If actual pressure is the same as your readings, I'd change the oil and add marvel oil to remove any deposits which may be on the pump pickup screen. Check oil you drained for fuel smell to make sure it's not contaminated.
If pressure does not improve, or drops further, you are going to have to drop the pan and check for bearing wear.(pumps generally don't go bad...wear at the bearings allows pressure to escape) If you find any bearings out of tolerance, change them and the pump as it may have some internal scoring from debris.

Never less than about 10lbs.usually 30lbs or so  If less then either engine main bearings is badly worn or  or the relief valve inside the oil pump is stuck in the bipass mode.