On engines with belt-driven cooling fans, a fan clutch is often used to save energy and reduce noise. The fan clutch disengages slows or disengages the engine's cooling fan when extra cooling isn't needed. The fan pulls air through the radiator and air conditioning condenser when the vehicle isn't moving fast enough to provide adequate airflow for cooling.
St Augustine grass will go dormant when the soil temperatures fall below 55 degrees. If the soil remains warmer than 60 degrees all year, the grass will stay green. It will, however, slow in growth as the soil drops in temperature. Disadvantages of St Augustine grass. One of the disadvantages of St Augustine grass is its poor wear tolerance.
Several distinct advantages make fall the best time to plant cool-season grass seed. In early autumn, the soil is still warm from months of summer sun. This combination of warm soil, moderate day temperatures and cool evenings encourages fast germination and establishment of newly sown cool-season grass seed. Cool-season grass seed germinates best when soil temperatures are between 50 and 65 degrees Fahrenheit. This roughly corresponds to daytime air temperatures in the 60 F to 75 F range. An inexpensive soil thermometer, available at most garden stores, can help eliminate the guesswork.