When car is off oil level is full, when started it drops below low level and light comes on

Checking the oil level with the engine running is irrelevant and means nothing. It should go down when the oil pump is picking it up and sending it around the engine. When the warning light turns on, you have a pressure problem. That is often caused by nothing more than a faulty sending unit, but it can be due to worn engine bearings too. Your mechanic will start by measuring the actual oil pressure with a mechanical gauge. If it's okay, the sending unit is suspect.

THIS MAY NOT BE SERIOUS.....OR IT COULD BE!

IF YOU ARE EXPERIENCING FUNNY NOISES OR KNOCKING AT LOW PRESSURE FOR SURE, IT IS PROBABLY SERIOUS!

SOMETHING YOU DID MENTIONED HERE, IS HAVE YOU CHECKED YOUR OIL LEVEL.

WHAT I MEAN IS "YOU"---NOT "DAVE" DOWN AT THE "SUPER DOOPER LUBE" TWO MONTHS AGO!!! (THIS IS HOW SOME PEOPLE CHECK THEIR OIL!)

IT IS IMPORTANT TO CHECK IT AT MINIMUM, "WEEKLY" AS PROBABLY PRESCRIBED IN YOUR OWNERS MANUAL....AND ALSO IF YOU SUSPECT A PROBLEM OR YOUR GAUGE OR LIGHT SAYS YOU HAVE A PROBLEM! ANYTHING COULD HAPPEN WITHIN SECONDS, YOUR OIL PLUG FALLS OUT (INSTALLED WRONG) OR ROAD DEBRIS KNOCKS A HOLE IN YOUR PAN!.....IF OIL IS THE ISSUE, IMMEDIATELY SHUT IT DOWN!!!....NO LIMPING IT ANOTHER 500 FEET!

EVEN IF YOU "HAVE OIL"---YOUR OIL PUMP MAY NOT BE WORKING!

HAVE YOU KEPT UP WITH SCHEDULED CHANGES?

USING THE CORRECT OIL?

THIS IS WHAT YOU NEED TO DO NOW....THE PREVIOUS WAS JUST REMINDERS!

REMOVE YOUR OIL PRESSURE SENDER AND INSTALL A MECHANICAL OIL PRESSURE GAUGE---THIS WILL GIVE YOU A REAL ACCURATE READING AS TO WHAT YOUR ACTUAL OIL PRESSURE IS, AND IS DOING WHILE BEING DRIVEN.

A GAUGE SET UP SORTA LIKE MINE, OR AN AFTERMARKET UNDER THE DASH MOUNT (USED AS A PORTABLE, TEMPORARY TEST PLATFORM) WILL ALLOW IT TO BE RUN OUT FROM UNDER THE HOOD AND INTO YOUR WINDOW, SO YOU CAN WATCH IT AS YOU DRIVE, ON TOP OF THE DASH, OR IN THE SEAT BESIDE YOU.....MIGHT PICK OUT A PERTTY ONE, YOU MAY WANT TO MOUNT IT PERMANENTLY AND DO AWAY WITH THE ELECTRIC ONE!

IF IT SAYS EVERYTHING IS A-OKAY WITH THE MECHANICAL GAUGE

THEN MOST LIKELY YOUR SENDER IS DEFECTIVE (NORMALLY THE PROBLEM IN CASES LIKE YOURS)--- THE ACTUAL GAUGE IN THE DASH WOULD BE THE SECOND GUESS AS TO BEING BAD, OR THE WIRING IN BETWEEN

SOME PEOPLE JUST CHANGE THE SENDER AS THEIR "TEST", THAT IS FINE, UNLESS IT DOES NOT SEEM TO WORK OUT

I LIKE TO KNOW WHAT THE "REAL DEAL IS", BEFORE I BUY A PART....I CAN'T AFFORD A NEW ENGINE EITHER.......PARTS CHANGING IS KINDA A WEIGH IT OUT THING $$$/ TIME/ SATISFACTION WITH RESULTS.....OR YOU NOW HAVE A WORKING OLD SPARE PART!

I WAS TOLD THAT 4 PSI WAS ADEQUATE PRESSURE TO LUBE AN ENGINE, BY A LOCAL PRODUCTION ENGINE RE-BUILDER (I WOULD NOT WANT THAT MYSELF!) THE NORM IN MY '77 CJ 5 IS BETWEEN 40-60 PSI.....20 PSI IS WHEN I START GETTING ALERT AND READY TO REBUILD!

A "HIGH VOLUME" OIL PUMP IS AVAILABLE FOR MY ENGINE (MAY BE ABLE TO FIND ONE FOR YOURS TOO) I HAVE INSTALLED SEVERAL ON THIS AND OTHERS I HAVE OWNED PREVIOUSLY. THEY HAVE INCREASED MY PRESSURE, AND COST ABOUT $120 OR SO, JUST A GUESS, I GAINED MAYBE ANOTHER 60,000 MILES, BEFORE PRESSURE DROPPED OFF AGAIN.

THIS MAY BE AN OPTION FOR YOU, IF THE MECHANICAL GAUGE DOES PROVE THAT YOU DO HAVE WEAR AND TEAR, AND PRESSURE JUST AIN'T GONNA IMPROVE UNTIL YOU DO SOMETHING MECHANICAL. HIGH VOLUME PUMP/ INTERNAL BEARINGS/ OR A REBUILD

THIS LINK MAY HELP YOU OUT IN DIYing YOUR OWN STUFF

https://www.2carpros.com/questions/2007-ford-taurus-tune-up

XOILPRESSUREGAUGE

SEE MY PIC BELOW OF MY GAUGE

BE SURE YOU KEEP US POSTED...WE LIKE HEARING A GOOD ENDING!

THE MEDIC