CANROYAL ULTRA OUTBOARD OIL 4T 10W-30 is a superior quality, extra high performance marine diesel engine cylinder oil.This unique formulation has been specifically developed for engines running in a low sulphur heavy fuel oil (HFO) environment.This cylinder lubricant provides maximum protection from adhesive and corrosive wear at the higher operating temperatures and pressures of today modern crosshead engines, for maximum reliability. It employs additives with greater thermal stability and superior acid-corrosion protection. It has an optimum viscosity of over 20 cSt. at 100°C and low volatility for best lubricant distribution and film retention. Through the use of unique formulation technology, the higher viscosity is attained with little or no use of thermally less stable, deposit-producing bright stock. Advanced technology at the 40 TBN alkalinity level has demonstrated excellent ring and liner wear protection and cleanliness under sustained operation with fuel sulphur levels from less than 0.3% up to 1.5%.