Preheating Cooler?

I was wondering. most people here advocate the practice of preheating your cooler tun to prevent gross heat loss when mashing. But even with that practice still recommend heating the water about 10-12 degrees warmer than your intended mash temp.

The problem I found when doing my first AG last weekend is that when i preheated the tun, the water temp only dropped by 6 degrees after everything was doughed in. I preheated it w/ 1 gal of boiling water, closed lid, the whole time it took for me to heat up my mash water.

Now, is the heating to 10-12 degrees warmer than intended mash temp for coolers that ARENT preheated, or is that what people usually lose in heat in an a PREHEATED cooler? Do I just adjust for my cooler then?

Like next time, knowing I'll only lose 6 degrees in my cooler preheated w/ boiling water, should I just heat my mash water to 160 to get to 154 mash temps, or is it just safer to end up higher than intended, and drop the temps to what you want by adding cold water?

What I do is add some of the hot water to my MLT (not boiling- I did that once and it warped my cooler) and let it sit until it falls to the strike temperature. Then I add my grain (which was in the basement, so the grains are about 55 degrees) and then add more strike water. This works perfectly for me and I always hit my temperatures by using the Beersmith calculations and the preheated MLT with the cool grain.

As you found out, everyone's system is different, so you can do what you find works out best for you. I would guess that most of us strike 9-11 degrees warmer than we are planning for the mash temp, and I also think most of us are using preheated tuns.

when i did it i dumped out the water in the cooler into the pot for my sparge water, before i added my mash water and grains to the cooler. I dont know where i heard to preheat my cooler w/ boiling water, but i know i did, or else i wouldnt have done it LOL. But now knowing that theres a possibility it might warp my cooler, i'm not doing that anymore.

The intended mash temp is an achieved equilibrium between the temperature of the strike water and temperature of the grain. The brewing software that I use calculates the strike temperature based on the intended mash temp, temp of the grain, thermal mass of the MLT and other variables to really dial in accurately.

The temps outside the MLT will also affect the degree of heat loss, as you will see when you brew across multiple seasons.