xpro

I'm planning to change my radiator and in the process I'll be draining as much coolant as possible. How many gallons of pre-diluted coolant should I have on hand before starting the job?

Gerf

If you buy 3 gallons you will have enough with some left over for top ups.

salimshah

I posted DIY thread in the hybrid sub-forum. You can skip the inverter part.
For non-hybrid ... 2 Gallons is cutting it close [assuming you plan to drain the engine block]. I will go on the limb and say if you leave the overflow-reservoir alone you will be able to do the job in 2 gallons. If you leave the block alone, you will have left over [if you purchase 2 bottles].

Salim

PS: Talk to the seller and see if they would accept an un-used/unopened bottle for a full refund. Also expect that you would need a 1/2-3/4 of a cup to fill out the trapped bubbles in few days.

Sweeks2020

I would measure the volume that came out and replace it with the same/similar amount. Then check to see if needs topping up.

I'm starting to do all my fluids esp the sealed transmission (with no dipstick).