Synthetic; 1 quart (946cc) bottle. The number one Heavy Duty and High performance oil supplement in the US. Eliminates dry starts and resists thermal breakdown in new engines. Raises oil pressure and adds lubricity. Can be used in engine and transmission. Should be mixed with a 20% to 60% ratio with other oils, depending on application. At that point the entire oil mix becomes much slicker than oil alone. The reduced friction will reduce fuel consumption and since reduced friction means reduced heat, it extends oil life by at least 50%. This regular heavy duty oil stabilizer is made from synthetic oil but will safely mix with all mineral and synthetic products.