The Prevost owner's manual that I had for my 92 XL (91 chassis) had a limit of 1,200 degrees for the pyro's. The manual indicated that normal operating temperature (coolant) for the 8V92 is 180 to 195 degrees. It also stated that the engine is not considered to be overheating until it hits 215 degrees. However, I would have freaked out if the temperature got above 200 degrees given my prior experience with catastrophic engine failure. In the old XL, we could run all day long in the Texas summers with the bus air on and stay just below 195. If we were climbing hills, the bus seemed to stay at or below 195 degrees if I kept the pyros between 900 and 1,000 degrees and turned the bus air off. This required downshifting to keep the rpm's up around 1,800 and didn't make us the faster one to the top of the hill, but we got there.