Guide to Checking Fluids

Checking the fluids in your car is an easy way to keep things running smoothly. Fluid leaks and contaminations are often easily avoidable with the proper attention. Checking your car’s fluids once per month is a great practice to be in.

To check the fluids in your car, you’ll start with your car’s manual. This will show you where each fluid reservoir and dipstick is located.

This article will show you:

  • How to check engine oil
  • How to check brake fluid
  • How to check power steering fluid
  • How to check coolant
  • How to check transmission fluid
  • How to check differential fluid

How to Check Engine Oil

Your engine oil, or motor oil, cleans your engine’s parts and keeps things cool and lubricated. You may be wondering if you should check the motor oil with the car on or off. The best time to check the motor oil is either before you turn on the engine, or 10 minutes after turning off the engine when the engine is cool. Ensure the vehicle is parked on level ground. This is so all the oil can be in the oil pan, and you can get an accurate measurement.

It’s important to check the oil monthly. If you think your car leaks or burns oil, check it more often. Each car takes a different type of oil and requires oil changes at different time intervals. Some cars may have performance specifications to meet, such as GM dexos1 Gen 2, or API SP. To know the proper schedule for your car, check your owner’s manual.

Once the car is cool and you’ve located the car’s dipstick per the owner’s manual, remove the dipstick from the engine. Wipe off the oil that’s on the dipstick, and reinsert it into the engine, ensuring it sits all the way in the hole. Remove the dipstick a second time and check the oil level. Use the indicators on the dipstick to check for the proper oil level. If your oil is low, fill up the oil reservoir, and recheck the oil level.

Checking the Oil Condition

Not only does the amount of oil you have in your engine matter, but the condition of the oil matters as well. An oil analysis is the most thorough way to check your engine oil’s condition, but a visual check of your oil is also beneficial. The ideal color for engine oil is translucent or amber colored. This shows that the oil hasn’t accumulated many hours or miles. Black oil means the additives in the oil have reacted properly and are holding the contaminants in suspension from your engine. Black oil means the oil is doing its job.

If your oil is thin, you may have fuel dilution. This happens when the gasoline or diesel from your vehicle contaminates the motor oil. If this is the case, the oil will typically smell like gasoline. A used oil analysis is the best way to figure out if you have a fuel dilution problem.

If your oil is frothy or looks like chocolate milk, you probably have water or coolant contaminating your oil. This means you most likely have a head gasket leak or other large problem, so seek a mechanic as soon as possible.

If the oil is gritty, it means it contains contaminants that bypassed the oil filter, most likely because the filter was full to capacity. This means it’s time to change the oil.

How to Check Brake Fluid

It’s a good practice to check your brake fluid with every oil change. In most cars, the brake fluid is in a small, clear reservoir near the firewall. It will have “min” and “max” indicator lines on the outside, so you should ensure the fluid is between those levels.

If your brake fluid is low, you can top it off. Check your owner’s manual to ensure the fluid you’re adding is the proper DOT classification.

How to Check Power Steering Fluid

Checking your power steering fluid is just like checking your brake fluid, and you should do it with every oil change. The reservoir is typically located next to one of the fenders. Check the reservoir to ensure the fluid is between the “min” and “max” levels. Some cars will say “full hot” or “full cold” on the reservoir. When you’re checking the levels, ensure you’re checking the fluid with your car either warm or cold in conjunction with the markings.

On some cars, the power steering fluid reservoir will have a small dipstick. If this is the case, remove the cap and check the fluid with the indicators on the dipstick.

How to Check Coolant

It’s a good practice to check your antifreeze, or coolant, monthly. It’s very important to ensure your engine is cool before attempting to check your coolant. The liquid will pressurize when the engine is hot, and the fluid can burn you. Let your vehicle sit for a few hours before you check your coolant.

First, locate the coolant reservoir. It’s a large plastic tank near the radiator. There are “min” and “max” indicators on the outside of the tank, and you’ll want to ensure the fluid level is between the two indicators. If the coolant level is low, you can top it off. Check your owner’s manual for the proper coolant to use.

While you’re checking your coolant, you can also remove the radiator cap to check that the coolant reaches the bottom of the filler neck. Check to see that the coolant is in good condition. Slime or sludge in the radiator is a sign of coolant contamination.

How to Check Transmission Fluid

Transmission fluid is as important as engine oil—it protects your car against gear and clutch wear, fights sludge build up, and cools hot-running components.

When you check your transmission fluid, your engine should be warm and idling, and your car should be in park on flat ground. Put your foot on the break, cycle through all your gears, place the car back in park, and put on the parking brake. It’s also good practice to chock the wheels to prevent any accidental car movement.

Check your owner’s manual for the location of your transmission fluid. If you have a dipstick, pull it from the tube. Wipe the dipstick clean, reinsert it to the tube until it’s sealed, then withdraw the dipstick again. Check the fluid levels with the indicator on the dipstick. You may need to top off the transmission fluid. Check your owner’s manual for what type of fluid to use. If you do need to top off the fluid, you’ll likely need a funnel as the dipstick tube is often the fluid fill hole.

Some cars have a “filled-for-life” transmission. This means the engine should not need transmission fluid checks, so they will not have a dipstick. Despite this, it’s a good practice to change the transmission fluid at least one time in the car’s life.

How to Check Differential Fluid

Many cars can go 100,000 miles without needing their differential fluid changed. Some newer cars don’t require fluid changes at all, so they don’t come with fill or drain plugs for checking the fluid. Because of this, it’s easy to neglect checking your differential fluid; however, keeping an eye on it will keep your car running smoothly.

First, locate the fill plug. It’s usually halfway up the differential cover. For help locating the differential cover, look in your car’s manual. Some cars will have two separate plugs for draining and adding fluid, while other cars have one fill port and require the removal of the full cover to drain the fluid. Clean the mud and dirt from the fill port, then remove the fill plug. In many cars, you’ll need a 3/8” hex plug to do this. Insert your finger into the fill port to check for the fluid level. It should be up to the bottom of the fill port. If you need to add fluid, check your owner’s manual for the fluid viscosity your car takes, as well as the gear lube you need.

If you do need to change the differential fluid, we recommend the AMSOIL easy-pack. Instead of fidgeting a standard plastic bottle into place and squeezing the contents into the differential or using a frustrating and messy gear-lube pump, the AMSOIL easy-pack reduces mess, hassle, and fluid waste.

With the proper fluid attention, your car will keep running smoothly for years to come.