2006 Subaru B9 Tribeca Owner's Manual - Page 306

11-10 Maintenance and service API classification SM (or SL): SAE viscosity No.: 30, 40, 10W-50, 20W-40, 20W-50 Cooling system -30 -20 -10 -20 0 20 0 40 10 20 30 40 60 80 100 5W-30* 10W-30, 10W-40 B00016 Never attempt to remove the radiator cap until the engine has been shut off and has cooled down completely. Since the coolant is under pressure, you may suffer serious burns from a spray of boiling hot coolant when the cap is removed. SAE viscosity number and applicable temperature *: 5W-30 is recommended. Engine oil viscosity (thickness) affects fuel economy. Oils of lower viscosity provide better fuel economy. However, in hot weather, oil of higher viscosity is required to properly lubricate the engine. Recommended grade and viscosity under severe driving conditions If the vehicle is used in desert areas, in areas with very high temperatures, or used for heavy-duty applications such as towing a trailer, use of oil with the following grade and viscosities is recommended. The cooling system has been filled at the factory with a high quality, corrosion-inhibiting, yeararound coolant which provides protection against freezing down to -33°F (-36°C). For adding, use genuine SUBARU coolant or an equivalent: a mixture of 50% soft water and 50% ethylene-glycol basis coolant. Use of improper coolants may result in corrosion in the cooling system. It is important to maintain protection against freezing and corrosion, even if freezing temperatures are not expected. Never mix different kinds of coolant.