Check your transmission fluid with the engine running and warm
To check automatic transmission fluid, start your car and let it idle for a minute or two so the fluid warms up. Warm fluid gives you an accurate reading — cold fluid sits lower on the dipstick and will tell you the level is lower than it actually is. Once the engine is warm, keep it running while you pull the dipstick, wipe it clean, reinsert it fully, and pull it out again to read the level.
The reason you check with the engine running is that transmission fluid circulates through the system when the car is on. When the engine is off, some fluid drains back into the pan, so the dipstick reading will be artificially low. If you check a cold, parked car, you might think you need fluid when you actually don't.
Most automatic transmissions sit in the engine bay toward the back, and the dipstick handle is usually bright yellow, red, or orange so you can spot it easily. If you cannot find it, your owner's manual will show you exactly where it is, or you can search your vehicle's year, make, and model online.
Key Takeaways
- Always check transmission fluid with the engine running and warm, because cold fluid gives a false low reading.
- Pull the dipstick all the way out, wipe it completely clean on a lint-free cloth or paper towel, push it back in fully, then pull it out again to read the true level.
- The fluid should reach the "full" mark on the dipstick — most dipsticks have two marks, one for "full" and one for "add" or "low".
- If the level is at or below the "add" mark, you need to pour in the correct transmission fluid type for your vehicle, which you will find in your owner's manual.
Locate the transmission dipstick in your engine bay
Open your hood and look toward the back of the engine compartment. The transmission dipstick handle is usually a bright color — yellow, red, or orange — and it sticks up from a tube that runs down into the transmission pan. It will be separate from the engine oil dipstick, which is typically closer to the front of the engine and often has a different color handle.
If you are unsure which one is the transmission dipstick, check your owner's manual or search online for a diagram specific to your vehicle's year, make, and model. Pulling the wrong dipstick will give you useless information and waste your time.
Pull the dipstick and wipe it completely clean
Grasp the handle firmly and pull the dipstick straight up and out of its tube. You will feel some resistance — that is normal. Once it is out, look at the fluid on it. Transmission fluid is usually bright red or pink when new, though it darkens over time.
Take a clean, lint-free cloth or paper towel and wipe the dipstick from top to bottom. Remove all the fluid so you can see the markings clearly. Any lint or debris left on the stick will make the reading harder to read accurately. If you use a cloth that sheds, you risk leaving fibers in the transmission fluid, so paper towels or a clean rag are your best choice.
Reinsert the dipstick fully and read the level
Push the dipstick back down into its tube until you feel it seat at the bottom. It should go in smoothly and stop when it is fully inserted. Do not force it — if it is not going in easily, you may have it at a slight angle. Straighten it and try again.
Once it is fully seated, pull it out again in one smooth motion. This time, look at where the fluid line sits on the stick. Most transmission dipsticks have two marks: a "full" line and an "add" or "low" line. The fluid should reach the "full" mark. If it is between the two marks, you are low but not critically so. If it is at or below the "add" mark, you need to add fluid.
Add transmission fluid if the level is low
If your dipstick shows the fluid is low, you will need to add the correct type of transmission fluid for your vehicle. Check your owner's manual to find the exact specification — common types include Dexron, Mercon, and CVT fluid, and using the wrong type can damage your transmission. The manual will also tell you how much fluid to add.
Locate the transmission fluid filler cap, which is usually on top of the transmission or nearby on the engine block. It is often labeled "transmission fluid" or "ATF" (automatic transmission fluid). Remove the cap and use a funnel to pour in the fluid slowly. Add a small amount, then recheck the level with the dipstick using the same warm-engine method. It is easier to add more fluid than to remove excess, so go slowly.
Once the level reaches the "full" mark, replace the cap and close your hood. Check the level again after a few days of driving to make sure it has not dropped further, which could signal a leak.
Understand what the fluid color tells you
Transmission fluid that is bright red or pink is in good condition. Fluid that is dark brown or black, or that smells burnt, means the fluid has broken down and needs to be replaced. This is different from checking the level — a transmission fluid flush or change is a separate job that usually requires a shop, though some people do it at home.
If your fluid is dark and you are also noticing transmission problems — hesitation, slipping, rough shifts, or delayed engagement — the fluid condition may be part of the issue. In that case, have a mechanic inspect the transmission, because old fluid alone does not always mean the transmission is failing, but it is a sign that maintenance has been delayed.
Check your transmission fluid regularly
Make checking your transmission fluid part of your routine maintenance, ideally once a month or before a long trip. Transmission fluid does not burn off the way engine oil does, so if the level drops noticeably between checks, you likely have a leak. A small leak might just be a loose fitting or a worn seal, but it should be inspected before the transmission runs dry.
Some newer vehicles have sealed transmissions with no dipstick. If you cannot find a dipstick, check your owner's manual to see if your transmission is sealed. Sealed transmissions are designed to go the life of the vehicle without fluid changes, but if there is a leak or a problem, you will need a shop to check the level using a scan tool or by removing a plug from the transmission pan.
Frequently Asked Questions
Can I check transmission fluid when the engine is cold?
You can, but the reading will be inaccurate. Cold fluid sits lower on the dipstick, so you will think the level is lower than it actually is. Always warm the engine first by letting it idle for a minute or two, then check with the engine still running.
What if I cannot find the transmission dipstick?
Check your owner's manual first — it will have a diagram showing the exact location. If you do not have the manual, search online for your vehicle's year, make, and model plus "transmission dipstick location." Some newer vehicles have sealed transmissions with no dipstick at all, in which case a shop will need to check the level for you.
How often should I check my transmission fluid?
Check it once a month or before long trips. Transmission fluid does not burn off like engine oil, so if the level drops between checks, you may have a leak that needs attention. If the level stays steady, you are in good shape.
What type of transmission fluid should I buy?
Always check your owner's manual for the exact specification your transmission needs. Common types include Dexron, Mercon, and CVT fluid. Using the wrong type can cause shifting problems or damage the transmission, so do not guess or substitute.
Is dark transmission fluid a sign I need a new transmission?
Dark or burnt-smelling fluid means the fluid has broken down and should be replaced, but it does not automatically mean the transmission is failing. However, if you are also experiencing transmission problems like slipping or rough shifts, have a mechanic inspect it, because old fluid combined with other issues may point to a larger problem.