Transmission fluid is as important as engine oil, but far fewer people check it. Low or burnt fluid causes rough shifts and, left alone, expensive transmission damage.
Know your car first
Many older automatics have a dipstick you can check yourself. Many newer cars have a sealed transmission with no dipstick, checked only from underneath at a service. Check your manual before you start.
How to check with a dipstick
Most automatics are checked with the engine warm and running, in park or neutral, on level ground. Pull the transmission dipstick, wipe it, reinsert and read the level against the warm marks. It should sit in the correct range.
Read the colour and smell
Healthy automatic fluid is red or pink and fairly clear. Dark brown fluid that smells burnt means it is overdue for a change and the transmission may have been running hot. That is a warning sign worth acting on.
Frequently asked questions
How often should transmission fluid be changed?
It varies widely, from around 30,000 to over 100,000 miles depending on the car and use. Follow the manual, and change sooner if it looks dark.
Can low transmission fluid cause slipping?
Yes. Low fluid causes slipping, harsh or delayed shifts, and overheating, so keep it topped to the correct level.
See our car accessory guides for tools and fluids.
