2000 Silverado 5.3 w/ 21k miles and original coolant

[Islandvic]

My 2000 Silverado 5.3 has 21k miles.

It has the original coolant.

No discoloration.

I believe its GM's 5yr/100k mile coolant.

Should I drain and refill with premix 50/50?

If so, what do yall recommend?

 

[Bill in Utah]

I flushed mine out with distilled water and put 50/50 dex cool back in. No problems.

Mine was looking like new when I took it out.

You're lower mileage than mine... I'm at only 38k.

Take care, bill

 

[Rhymingmechanic]

I flushed at 3 years and 39k miles. There was just a little brownish buildup in the overflow tank, above coolant level. The coolant looked fine. I refilled with distilled water and the orange Prestone long life. Coolant appearance and level are the same a year later.

 

[Ryan00TJ]

I change my LS1's coolant every 3 years or 60K miles. Drain radiator and refill w Wallmart $.59 jugs distilled water. Turn heater on and run engine until Tstat opens and coolant circulates from radiator through entire engine. Repeat process until fluid draining out of radiator is clear.

From there the block passages and heater core and hoses are full of fresh distilled water. Calculate proper amount of Prestone Dexcool coolant and add to radiator. Fill overflow tank with 50/50 mix distilled and Dexcool. HTH