Combustion Chamber
A brand new engine requires an octane level determined by its design and the quality of its manufacturer. The engine's octane number requirement (ONR) increases as combustion chamber deposits form during the first several thousand miles of operation. If the increase is large enough, the engine manufacturer's recommended octane level may no longer prevent knocking. If the vehicle is equipped with a knock sensor, it may experience a loss of power.

Research has shown that precursors for combustion chamber deposits come from the fuel, some fuel additives and the engine oil, and that certain fuel and engine oil components form more deposits than others.

Combustion chamber deposit interference (CCDI) and combustion chamber deposit flaking (CCDF) are two other problems which sometimes occur in certain modern engine designs. CCDI is the result of physical contact between deposits on the piston top and cylinder head and is manifested as a loud, metallic banging sound when the engine is cold. CCDI is limited to the engines that have been designed primarily to reduce emissions, with minimal clearance—one millimeter or less—between some areas of the piston top and the cylinder head (squish areas) when the piston is at top dead center. Combustion chamber deposit flaking causes low-compression pressures to result due to improper sealing of the valves. This problem occurs when pieces of CCD flake off and end up lodged between the valve face and the valve seat. Typical symptoms of CCDF are difficulty in starting and rough running when cold.

About half of the cars and trucks on the road today have engines that are equipped with a device called a knock sensor. A knock sensor is designed to detect knock, often before the driver does. Upon sensing knocking or pinging, the engine's computer control system (engine control module or ECM) adjusts the engine's operation (retards the spark timing) to avoid the knock. These adjustments can reduce power and acceleration under certain driving conditions, especially under heavy acceleration when you want power the most.

Since excessive combustion chamber deposits can promote knock, they can also suppress your engine's full potential by contributing to more frequent knock-sensor operation. Texaco and Chevron gasolines with Techron are unbeatable at preventing harmful combustion chamber deposits, helping your engine maintain the maximum performance for which it was designed.

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