OK, looking to replace front O2 sensor. Know to avoid Bosch. So here are my choices:

New AC Delco for $58 shipped
New Standard Motor Products for $33 shipped

Which would you do?

AC Delco or Denso. In that order.

Go with the Ac Delco & $58 shipped sounds like a heck of a deal too!

Ed

My new AC Delco improved my fuel economy so much (+33%) that it paid for itself in a few months. The Delco brand worked well for me.

what delco # is that, cause I just paid 75 for mine and it did nothing for my mileage. My old one had 290K on it an it turned out to be fine.

Can someone explain to me (in plain english) what the O2 sensor does and how to know if it needs replacement?

Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.

A gasoline engine burns gasoline in the presence of oxygen (see How Car Engines Work for complete details). It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine'* computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

OK, thanks for that. Since my car is running just fine the sensor is probably good to leave alone for awhile longer.

Is there any particular time frame for changing them? Odometer reading where they tend to start messing up?

no time frame. I changed mine because I thought by 290K a new one would certainly be better. I feel I wasted the money.

Most start getting tired around 50k-60k miles. (you do the conversion for )

We typically advise used car buyers to change it if they get worse than 28mpg on the freeway (long flat freeway trips) or if it'* over 50k old, or if they don't know if it'* original.