I need to drain the gas tank to fill with premium gas & drive for 50 miles to reset the emissions computer.

If the pump will still run, you can open a fuel line, maybe use hose on line to aim down into a container and drain that way. Don't take any lines loose unless your sure no pressure on the system. Sometimes you can get under vehicle remove fill hose from gas tank, then use a siphon hose in the gas tank. Your local auto store probably has a plastic siphon hose, that has a squeeze bulb on it to create a siphon, so you don't have to use your mouth. I don't know if that will reach down the fill tube? In my younger years, they called a siphon hose an okla credit card. I'm almost 70 now, don't like getting gas in my mouth.lol

They allow one not ready,how many do you have?try to reset and how far you can go before light come back.Maybe two,2002 down allow ?

Usually 100 miles give or take.
But its not the mileage as much as the driving conditions.
The car has to be driven at various speeds and at operating temp for the computer to test emissions components.
So something like 50 miles of city driving and 50 miles of highway AFTER the engine is warmed up.

If the old gas is bad you should remove the tank, dump the gas, and clean the inside of the tank. You may have to siphon the gas to get to the point where you can manage the tank to remove it.

Cars and trucks manufactured since the late 70's have anti-siphoning screens at the bottom of the fill tube to the tank. So, sorry to say, no you can't siphon this new gas. I can truly commiserate with you as it's happened more than once. I've just filled my tank and the vehicle bites the big one. The only way to get to that gas is to drop the tank.

50/50...
tries to fill the tank and don't mount filler cap into gas tank. don't leave immediately the gas station but go after 5 minutes and see if the problem appear more than 2 miles.
deactivates the carbon filter before filling the tank completely
If the problem recurs with fuel cap without being mounted, IT IS NOT charcoal filter

Ouch!
Did you run the car?
Instead of siphoning, look for a drain, and be sure to flush all of that gasoline out of lines from the tank to the injectors!
Check tdiclub.com forums- It's a very helpful community.

One tank of gas is not enough to compare mileage. Or are you saying the computer's readout of mpg estimate is showing less? Try a tank or two of premium and see if that helps. Keep track of gas mileage. Driving techniques have a lot to do with gas mileage, as does long trips vs. short trips, highway cruising vs. city driving. For best mileage, do regular maintenance and keep the car in top running condition-good spark plugs and clean filters and clean oil ! Attend to minor problems before they escalate.
If you want to check actual miles per gallon, start with a full tank. Write the odometer reading down, and go. Everytime you put gas in, write down the amount. When you are close to 1,000 miles from the time you started, go fill the tank and include that amount of gas to your previous list. Now add up all the gas used and divide it into the miles to get miles per gallon. (976 miles/31.8 gallons = 30.69 mpg ) . Only one tank will skew your numbers, might be off cause the tank was filled more to the top than the previous fill-up. About a thousand miles of driving will give you a very accurate figure of miles per gallon for your car.

If you can siphon and gas and put in a glass container like a small glass...let it set for a few minutes and if it is bad gas it will separate but only do this if you really think that is what it is. Use a siphon bought from a parts store and not to put in your mouth. If it separates you have 2 options...1 drain the tank which can be dangerous and 2 get a few bottles of water remover from the same parts store that you bought the siphon.

drain the tank change the fuel filter motor will be fine
it'll run funky until the e85 is flushed out