Cool season turf is even more sensitive to being burnt than say, bermuda or zoysia down south. I suggest no more than 0.25 lb N in 5 gallons per 1000 sq ft. If you are doing this to a drought stressed lawn, all bets are off.
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
Benjamin Franklin 1775
Sell not virtue to purchase wealth, nor Liberty to purchase power.
Benjamin Franklin Poor Richard's Almanac1738