How much does bad plug wires. bad 02 sensors and old pcv valves affect gas milage? When you change transmission fluid how much does the trans pan hold? What is the purpose of drilling a 180 thermostat?I have a 2000 SSEi with 74000 milage on it . Only mods is a 180 thermostat and a 3.4 pulley.

Unfortunately, there'* no quick and easy answer as far as a figure for your question. However, each (depending on how bad) except for the pcv valve, can significantly affect both fuel mileage, and performance.

The O2 sensor helps the computer decide the proper air/fuel mix and has to respond quickly enough for the information to be useful.

Spark plugs and wires - if each cylinder isn't firing properly, that means the fuel sent to that cylinder is wasted by not being burned, and does nothing to add to the power the engine makes.

If the intent of your question is to find out if it'* time for replacement, the short answer based on mileage alone is: O2 yes (ACDelco or Denso); plug wires - yes (NAPA Belden or other good quality wires - Taylor'* have been known to have a problem.); plugs - coming up on it. No Bosch or platinum plugs. PCV - pull it, shake it, see if it rattles. If it does - it'* likely ok.

I just dropped my pan last weekend and I'll confirm the 7.6 quarts. I bought 2 one gallon jugs of Dexron VI and I have less then a quart left.

Sorry that I missed that question the first time. Like the others, I used just under 8 quarts each time I changed mine.