Do you add fluid when car is started or not?

Answer 1

That depends on the fluid being added:

Automatic Transmission Fluid (ATF) should be checked after the engine/transmission are warm (has been driven several miles) and fluid can be added while the engine is running. After new fluid is added, the trans should be shifted through all the gears (Park - Reverse - Neutral - Drive - 2nd - 1st - 2nd - Drive - Neutral - Reverse - Park) stopping for a moment in each gear to allow the transmission to get 'in' to the gear, and placed back in Park before rechecking.

Oil should be added without car running, then started and run for a few seconds, turned off and recheck.

Antifreeze should be added to a cold engine, and can be added when you first turn car on, but after the thermostat opens (warm/hot engine) the level will drop and you can overfill it (excess will run out of the reservoir when it cools back off due to pressure it creates). Antifreeze is typically added to the reservoir to the indicators on bottle.

Manual Transmission Fluid does not require engine to be on or off.

All other engine fluids (Brake, Power Steering) should be added with engine off.

Windshield washer fluid can be added at any time.

Hope this helps...