Most people understand how important it is to change their car’s engine oil and filters, but transmission fluid doesn’t always come to mind. The question of how often to get a transmission flush depends on a variety of factors.

• For a manual transmission, most manufacturers say you need to change the fluid every 30,000 – 60,000 miles.
• Most people these days have an automatic transmission, and that’s trickier to understand. Some vehicles may never have their transmission fluid changed, unless there’s a leak or another problem. Other engines have a regular maintenance interval, just like engine oil or filters.

It is important to follow the manufacturer’s guidelines on transmission maintenance. If you need to have the transmission rebuilt, that can run you up to $6,000 or more.

Read our expert article for more about when to change your transmission fluid.

The first thing to determine is whether you can check the fluid at all. Many modern cars don’t have a transmission fluid dipstick, so the only way to check it might be to leave it to the pros.

But if your car does have a dipstick, here are a few things to keep in mind.

1. First and foremost – and this is always good advice – consult your owner’s manual.
2. Park your vehicle on a flat surface.
3. Based on the owner’s manual, decide whether to checking the transmission fluid with the engine on or off. Obviously, you’ll have to be a lot more careful if the engine is running.
4. Apply the parking brake for safety and make sure the vehicle is in Park.
5. Find the transmission dipstick, which is usually brightly colored and toward the back of the engine.
6. Remove the dipstick, being careful not to spill or drip any fluid. Wipe off the dipstick with a clean rag, just as you would do when checking the engine oil.
7. Reinsert the dipstick, then remove the dipstick again to check the fluid level.
8. If you need to top it off, be sure to use the recommended transmission fluid. If the fluid is particularly low, you might have a leak and should get it checked out.
9. Replace the dipstick once you verify that the transmission fluid is at the right level.

The cost for transmission fluid change or flush really depends on whether you’ve got a manual transmission, automatic transmission or continually variable transmission (CVT). That will dictate the amount of fluid you need and, based on the engine, what it takes to change it.

There’s also a difference between a transmission fluid change and a transmission fluid flush.

• For a fluid change, your service center allows some of the fluid to drain out (maybe as little as 30-percent) and then they add fluid to fill it back up.
• For a fluid flush, things get more intense. The technician uses a machine to extract all the transmission fluid out, pumps special solution through the torque converter and cooler lines until it runs clean, and THEN fills the transmission back up.

Prices can vary widely, but in general, a transmission fluid change would be $150-175 and for a transmission fluid flush, expect to pay around $165-$290.

Of course, that’s only an estimate. If your fluid is in particularly poor condition (through neglect or contamination), your bill could be higher.

One thing is for sure: Whatever it costs to change or flush your transmission fluid, it’s going to be cheaper than a major transmission repair or rebuilding the transmission entirely.

CVT (or Continuously Variable Transmissions) don’t have the fixed gear ratios of most automatic transmissions. They just work differently. But do you need to change the transmission fluid?

The short answer is Yes. Just like other automatic transmissions, you need to check, maintain and occasionally flush the transmission fluid on a CVT. Check your owner’s manual for more details.

Similar to the function that oil has in your engine, transmission fluid lubricates the moving parts in the transmission. When the fluid is worn out, contaminated or missing because of a leak, you’ll start to see – or, more likely, feel – problems with the way your transmission shifts.

• Difficulty in getting into gear or staying in gear
• A lurching or thumping when shifting. If it’s operating properly, you probably won’t notice your transmission doing its job; if you really feel the shifts, you may have an issue.
• A lag between pressing the accelerator and actually accelerating. A variety of different issues could cause this, but transmission issues could be one.
• Strange noises like whining or grinding.

If you suspect an issue, the best course of action is to take your car to your local service center to get it checked out.