Do you check transmission fluid with an engine running or not?

In most modern cars with automatic transmissions, you check the transmission fluid with the engine running and the transmission warmed up, usually in Park (P) or Neutral (N) as your owner’s manual directs. For manual transmissions, the check procedure is different and typically done with the engine off. Always consult your vehicle’s manual for the exact instructions.

Transmission fluid levels are temperature- and method-sensitive. Reading the dipstick while the fluid is cold or at the wrong temperature can give an inaccurate result, and using the wrong position can lead to overfill or underfill. The following guidance covers the common approaches for automatic transmissions and for manual transmissions (including CVTs), with reminders to follow the manufacturer’s exact procedure for your model.

Automatic transmissions: when and how to check

Before listing the steps, note that the standard procedure for most automatics is based on starting and operating the vehicle long enough to bring the ATF to its normal operating temperature. Always verify with your owner's manual for model-specific requirements.

1. Drive the car for several minutes to bring the transmission up to normal operating temperature, then park on level ground.


2. With the engine running, apply the parking brake and leave the transmission in Park (P) unless the manual specifies Neutral (N) for the check.


3. Pull out the ATF dipstick, wipe it clean, reinsert fully, then pull it again to read the fluid level.


4. Check that the fluid level is within the HOT marks on the dipstick. If your dipstick has a cold and hot range, ensure you’re reading the HOT range (readings can differ when the fluid is cold).


5. If the level is low, add the recommended ATF slowly through the dipstick tube (or fill port) in small increments, then recheck. Do not overfill.


6. Once the level is correct, wipe the dipstick and reinsert it, then remove the dipstick one final time to confirm the level reading and ensure the transmission is not leaking.

Concluding guidance: Reading the level with the engine running and the transmission at normal temperature helps ensure the fluid has circulated and expanded to its correct level. If you’re unsure about your vehicle’s specific steps, consult the owner’s manual or a qualified technician.

Manual transmissions and CVTs: what changes

Before this list, keep in mind that manual transmissions and CVTs (continuously variable transmissions) often use a different procedure from typical automatics. Many manuals require checking with the engine off and on level ground, while some newer manuals may specify a warm engine and different gear positions. Always follow the exact instructions in your manual.

1. Park on level ground and leave the engine off unless your manual instructs otherwise, then engage the parking brake.


2. Locate the transmission fill plug (and liquid level hole, if applicable) and remove the fill plug.


3. For most manuals, the fluid should be at or near the bottom edge of the fill hole. If the fluid is low, add the manufacturer-specified transmission fluid slowly until it begins to seep from the fill hole or reaches the proper level as described in the manual.


4. Replace the fill plug securely and clean up any spilled fluid. In some models, after refilling, you may need to start the engine and move through gears to settle the fluid; defer to your manual for this step.

Concluding guidance: Manual transmissions have tight tolerances and different fill procedures, so incorrect checking can lead to overfill or damage. If in doubt, have a professional check the level and perform any necessary service.

Practical tips and common pitfalls

To avoid common mistakes: always check on level ground, follow temperature guidelines, and use the correct type of transmission fluid for your vehicle. Fluid that is discolored, burned-smelling, or promises leaks should be inspected by a technician. If your car requires a professional service to adjust the level, do not attempt to overfill or use the wrong fluid type.

Summary

In short, for most automatic transmissions, you check transmission fluid with the engine running and the transmission warmed up, in Park or Neutral as directed by your manual. For manual transmissions, the check is typically done with the engine off on level ground, though procedures can vary by model. Always refer to your vehicle’s owner’s manual for model-specific instructions, and seek professional help if you’re unsure.

Should I check my transmission oil when the engine is hot or cold?

You should check transmission fluid when the engine is hot and running for an accurate reading, as the fluid expands when it heats up. It's crucial to park on a level surface, have the engine running in park or neutral, and check the level on the dipstick. 
This video shows how to check transmission fluid: 37sJiffy LubeYouTube · Jun 29, 2015
Steps to check the transmission fluid

1. Park on a level surface: and engage the parking brake. 
2. Start the engine: and let it run for a few minutes to warm up to normal operating temperature. 
3. Shift the gear selector: from Park, through the gears, and then back to Park or Neutral (check your owner's manual for the correct procedure). 
4. Turn off the engine: (if specified by your manual) and wait a few minutes for the fluid to settle. 
5. Pull out the transmission dipstick, wipe it clean with a lint-free cloth, and re-insert it fully. 
6. Pull the dipstick out again: and check the fluid level against the "hot" or "full" markings on the dipstick. 
7. Top off: the fluid if it is low, adding a small amount at a time and re-checking the level to avoid overfilling. 

This video demonstrates how to use a transmission dipstick: 59sWeberAutoYouTube · Mar 20, 2020

What is the correct way to check transmission fluid level?

To check your transmission fluid, park on a level surface with the engine running and warmed up, set the parking brake, and put the car in park. Locate the transmission dipstick (usually a yellow or orange handle), pull it out, and wipe it clean with a lint-free rag. Reinsert the dipstick fully, then pull it out again to check the level against the "hot" or "full" marks. Check the fluid's condition: it should be pink and clear; if it's dark brown or smells burnt, it needs replacing.
 
Step-by-step guide
This video demonstrates the complete process of checking transmission fluid: 48sJiffy LubeYouTube · Jun 29, 2015

1. Warm up the engine: Start the car and let it run for a few minutes to warm the transmission fluid to operating temperature, as this is when you should check the level. 
2. Park and secure the vehicle: Park on a level surface and engage the parking brake. Ensure the vehicle is in Park or Neutral. 
3. Locate the dipstick: Open the hood and find the transmission fluid dipstick. It often has a colored handle (like yellow or orange) and is typically located to the right of the engine oil dipstick, especially in front-wheel drive cars. Consult your owner's manual if you can't find it. 
4. Wipe and reinsert: Pull the dipstick out completely and wipe it clean with a lint-free rag or paper towel. Reinsert it fully into the dipstick tube. 
5. Check the level: Pull the dipstick out again and check the fluid level. It should be between the "COLD" and "HOT" marks if your engine is cold, or at or near the "HOT" or "FULL" marks if the engine is warm. 
6. Inspect the fluid: Look at the fluid on the dipstick. It should be a translucent pinkish color. If it's dark brown, murky, or has a burnt smell, it indicates a problem, and the fluid should be replaced. 
7. Add fluid if needed: If the level is low, use a funnel to add the correct type of transmission fluid slowly, rechecking the level frequently with the dipstick to avoid overfilling. 

You can watch this video to learn how to check transmission fluid in most cars: 47sLive FreeYouTube · Sep 25, 2018
Important considerations

• Manual vs. automatic: Most modern vehicles have an automatic transmission, but older or manual transmission vehicles may not have a dipstick. If your car is a manual or has a "sealed" transmission, you'll need a mechanic to check the fluid, often by removing a fill or inspection plug. 
• Safety: Transmission fluid can be hot, so be careful when checking it. 
• Correct fluid type: Always use the specific type of transmission fluid recommended in your owner's manual. Using the wrong type can cause damage to the transmission. 

Should I check my transmission fluid with the engine running?

Yes, for automatic transmissions, you should check the transmission fluid with the car running. It's crucial to let the engine warm up first, then shift through all the gears while keeping the brake pressed, and finally check the fluid level while the engine is in park or neutral. Checking while the engine is on ensures the fluid is circulating properly and the torque converter is full, giving a more accurate reading. 
This video demonstrates the importance of checking transmission fluid while the engine is running: 59sOBD InsightsYouTube · Sep 3, 2024
Why check with the engine running

• Accurate reading: The fluid circulates through the transmission, including the torque converter, while the engine is running. This prevents a false high reading that can occur if the fluid has drained back into the pan when the engine is off. 
• Hot fluid: Checking the fluid when the engine is warm gives the most accurate reading because transmission fluid expands as it heats up. Your dipstick often has separate "hot" and "cold" markings. 
• Functionality: The engine needs to be running to activate the transmission and its internal parts, which is necessary for a proper check. 

How to check automatic transmission fluid

1. Make sure the car is on a level surface and set the parking brake. 
2. Start the engine and let it run until it reaches normal operating temperature. 
3. Press the brake pedal and slowly shift the gear selector through all the gears (P, R, N, D, etc.), pausing for a few seconds in each. 
4. Return the gear selector to the park (P) position. 
5. Locate the transmission fluid dipstick, pull it out, and wipe it clean with a rag. 
6. Re-insert the dipstick completely, then pull it out again to check the fluid level against the "hot" marks. 

You can watch this video for a step-by-step guide on checking transmission fluid: 52sJiffy LubeYouTube · Jun 29, 2015
Important considerations

• Consult your owner's manual: The specific procedure can vary between vehicles. Some modern vehicles may not have a dipstick, or some may have different checking procedures. 
• Manual transmissions: The procedure for checking manual transmission fluid is different and typically requires the engine to be off and the vehicle to be on a lift. 
• Safety: Be careful when working around a running engine. Some sources recommend using wheel chocks for added safety. 

Does a Nissan have to be running to check transmission fluid?

First, put the gearshift in either neutral or park, leave your parking brake active, and turn on your engine. Your engine needs to be warm when checking your transmission fluid and should remain on during this process.