Need to know how often to add antifreeze - 2000 Toyota Avalon

it does not use antifreeze. you will need to buy Dexccol premixed 50/50 coolant. There is no universal coolant, use Dexcool only, it is red. you should never ever add water, only premixed coolant.
the premixed is good to -40 degrees F.

Open the container of antifreeze. Using a separate EMPTY gallon-size container, pour out HALF of the contents into the empty container, making sure not to spill any. Now, FILL the newly filled container with tap water. Fill the rest of the antifreeze with water, also. Now, you are ready to add antifreeze to your vehicle! Simply locate the radiator cap, (Don't touch it if it's hot!!) and unscrew it. Pour the desired amount of your mixed antifreeze into the radiator. Remember not to do this without proper knowledge!

Both if so equipped (has a radiator cap). First top off radiator, then run to operating temp and add to reservoir until at the proper level. Test drive several miles, recheck reservoir.

Add anitfreeze in the top of the radiator. Lift the hood in front, take off the radiator cap and add antifreeze until it is full. Purchase Prestone
50/50 pre dilluted antifreeze solution at WalMart.

It will need as much as it takes, which is impossible to tell depending on how you flushed it.
But your whole system takes more than 2 gallons, and since you want a 50/50 mix you know you will need more than one gallon of antifreeze. So you need to start by purchasing 2 gallons. If you have left over, it does not go bad. And if you do not quite have enough, you can probably add a little extra water because you probably did not flush all the antifreeze out.
Once you run it, then next time it will need more again after the heat bleeds the air out.

dexcool silicate free long life antifreeze.

Once you have located the overflow tank check to see if it has any antifreeze in it. You will be able to see it without taking the lid off and It is IMPORTANT to understand that if your engine has not been running for a while that the coolant level should be at the "COLD" level and if you are looking at it while the engine is warm or you drove the vehicle shortly before checking, it should then be at the "HOT" level.

Most likely, if there is fluid in the tank, you do not need to add any. Once you determine that you need to add more antifreeze, simply add it to the overflow tank. You do not need to add it directly into the radiator. NEVER REMOVE THE RADIATOR CAP WHEN ENGINE IS WARM, YOU MAY INJURE YOURSELF! When adding antifreeze, it is very important that you use the correct antifreeze! There are brands out there that you can use for all makes and models. Those should only be used when you are adding or "topping off" the antifreeze.

Please note that you can damage your engine if the wrong coolant is used! So I strongly suggest that you go to your local auto parts store and they will make sure that you get the correct antifreeze. You can also find this information in your owners manual. Make sure that you use the correct mixture, .The 50-50 pre-mixed antifreeze comes with water already in it so you don't have to add water. Good Luck.!

Most vehicle Mfg.'s do not want you to access the radiator, so they put in overflow tanks.
You can add coolant there. You will find it under the hood next to the interior fender.
Only check or add coolant when the engine is cool.
I would start looking for a coolant leak. Vehicles are not supposed to leak or lose their coolant.
Check for green coolant spots on the ground where you park your vehicle.
Please let me know what you find.

PRESTON SELLS A CLEAR ANTIFREEZE THAT MIXES WITH ALL TYPES,DO NOT USE DEX-COOL THOUGH THAT SPECIFIES TO GM OK.YOU CAN PICK THIS UP AT ANY OREILLY OR AUTOZONE.