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A device that detects the amount of oxygen in the exhaust gas (EG) of a fuel-injected engine and sends that information to ECM; also called, "oxygen sensor", "lambda sensor", "EGO sensor" or the abbreviated form "O2S". An oxygen sensor detects air to fuel ratios ("A/F ratio" or "lambda") from the oxygen concentrations in exhaust gas. The stoichiometric A/F ratio is about 14.7, where the amount of O2 is exactly equivalent to consume the supplied fuel in an engine. If fuel increases, engine power goes up and residual CO and H2 increases in the exhaust; if fuel decreases, power goes down and residual oxygen increases in the exhaust. The structure of a conventional O2 sensor is shown below. Its main body is a U-shaped tube of zirconia (ZrO2) electrolyte. Zirconia, a white water-insoluble powder, is a well-known oxygen ion conductor, at high temperatures. Platinum (Pt) electrodes were pasted on both sides of this zirconia tube. The inner electrode communicates with the atmospheric air and the outer side, with the exhaust gas. It is, actually, a potentiometric solid electrolyte cell.

An abbreviation used by car dealers to indicate "on approval of credit" or "on approved credit". Also used "OAC", "O.A.C." or "oac".

A newer crash test where the cars collide at right angles to one another as opposed to head-on. This test is more representative of common passenger car accidents as most cars collide at some kind of angle.

A known German engineer and experimenter. Nicolaus Otto built the first practical four-stroke internal combustion engine called the "Otto Cycle Engine" and, when he completed his engine, he built it into a motorcycle.

Nicolaus Otto was born on June 14, 1832 in Holzhausen, Germany, and his first occupation was as a traveling salesman selling tea, coffee, and sugar. After meeting Eugen Langen, a technician and owner of a sugar factory, Otto quit his job, and in 1864, the duo started the world's first engine manufacturing company N.A. Otto & Cie (now DEUTZ AG, Köln).

In May 1876, Nicolaus Otto built the first practical four-stroke piston cycle internal combustion engine. He continued to develop his four-stroke engine after 1876 and he considered his work finished after his invention of the first magneto ignition system for low voltage ignition in 1884. Otto's patent was overturned in 1886 in favor of the patent granted to Alphonse Beau de Roaches for his four-stroke engine. However, Otto built a working engine while Roaches' design stayed on paper. On October 23, 1877, another patent for a gas-motor engine was issued to Nicolaus Otto, and Francis and William Crossley.

Nicolaus Otto died at age 59, on January 26, 1891, in Cologne.