STP 64450EN Smoke Treatment for Petrol Engines 450ml. Reduces exhaust smoke and lowers oil consumption. Excessive oil burning and exhaust smoking can occur in older, worn engines when motor oil enters the combustion chamber and is burned along with fuel. This condition, known as oil blow by, often results when friction and metal-to-metal contact have worn parts and created gaps between the cylinder walls, pistons rings and valve guide seals. STP 64450EN Smoke Treatment provides a thicker oil cushion to help fill these gaps and reduce oil blow-by and smoking.