2021 Tesla Model S Fluid Specifications & Capacities

As an ASE-certified master technician, I’ve seen the automotive industry shift dramatically over the last decade. The 2021 Tesla Model S—available in both Long Range and the blistering tri-motor Plaid configurations—represents the pinnacle of this EV revolution. However, just because there is no internal combustion engine under the hood doesn't mean this vehicle is entirely maintenance-free. It still relies on highly specialized fluids to keep its battery cool, its reduction gears spinning smoothly, and its heavy chassis stopping safely.

If you are servicing a 2021 Tesla Model S, it is absolutely critical to understand that EV fluids are often uniquely formulated to account for thermal management and electrical conductivity. Using the wrong off-the-shelf product can lead to catastrophic battery or drive unit failure.

Below is the complete fluid specification guide for the 2021 Tesla Model S.

Quick reference

Fluid	Type/Spec	Capacity
Engine Oil	N/A (Electric Vehicle)	N/A
Engine (Battery/Inverter) Coolant	Tesla G48 (Blue-Green) or HT-12 (Green) 50/50 mix	12.0 – 15.0 Quarts (Verify with OEM based on trim)
Drive Unit Fluid (Front)	Dexron VI / Pentosin ATF 9 (Tesla Spec)	~1.5 Quarts (1.4 Liters)
Drive Unit Fluid (Rear)	Dexron VI / Pentosin ATF 9 (Tesla Spec)	~1.5 Quarts (LR) / ~2.5 Quarts (Plaid dual-rear)
Brake Fluid	DOT 4 Brake Fluid	~1.0 Quart (System Flush)
Power Steering Fluid	N/A (Electronic Power Steering)	N/A
Windshield Washer Fluid	Standard all-weather washer fluid	1.2 Gallons (4.5 Liters)
DEF / Transfer Case	N/A	N/A

Note: Capacities are approximate dry-fill guidelines. Always fill to the factory designated weep hole or maximum line and verify in owner's manual / OEM service info.

Battery and Inverter Coolant

In an internal combustion engine, coolant keeps the block from melting down. In a 2021 Tesla Model S, the thermal management system is arguably the most complex system on the car. The coolant loops through the high-voltage battery pack, the drive unit stators, and the power inverters.

Type and Spec: Tesla traditionally utilizes a G48 (blue-green) or newer HT-12 (green) ethylene-glycol-based coolant. It is an HOAT (Hybrid Organic Acid Technology) coolant. Common Pitfalls: Never mix OAT (like Dex-Cool) with HOAT coolants. More importantly, never use tap water or standard universal coolants. The coolant used in Teslas must maintain specific low-conductivity (dielectric) properties. If a highly conductive coolant is introduced into a system that directly cools high-voltage electrical components, it can cause isolation faults or short circuits, which will completely immobilize the vehicle. Tesla recommends checking the coolant level periodically, but the system is sealed; fluid replacement is typically only required if a component is replaced or a leak occurs.

Drive Unit Fluid (Transmission / Differentials)

While the Model S doesn't have a multi-gear transmission, transfer case, or traditional differentials, it does utilize reduction gearboxes bolted directly to the electric motors. These are known as Drive Units. In the 2021 Long Range, you have one front and one rear drive unit. The Plaid features one front and two independent rear drive units.

Type and Spec: The gears in these drive units spin at incredibly high speeds (up to 20,000 RPM). Tesla utilizes a high-quality ATF (Automatic Transmission Fluid) to lubricate the reduction gears and differential bearings. The factory spec is a Dexron VI equivalent, often filled with Pentosin ATF 9 or a proprietary Tesla synthetic fluid. Intervals and Pitfalls: Tesla considers this a "lifetime" fluid under normal conditions, but as a master technician, I highly recommend a drain and fill every 50,000 miles to remove metallic break-in wear and extend the life of the bearings. Never use heavy gear oils (like 75W-90 or 75W-140 with LSD additives) in these drive units. Thick gear oil cannot adequately lubricate the high-speed bearings and will cause extreme fluid friction, overheating the drive unit.

Brake Fluid

Because EVs use regenerative braking (using the electric motors to slow the car and recapture energy), the mechanical friction brakes on a Model S are used far less frequently than on a gas car.

Type and Spec: Tesla specifies heavy-duty DOT 4 brake fluid. Intervals and Pitfalls: While the brake pads last a very long time, the brake fluid does not. DOT 4 is highly hygroscopic, meaning it absorbs moisture from the atmosphere. Because the mechanical brakes aren't generating as much heat on a daily basis (which normally helps boil off minor moisture), water accumulation in the brake lines is a major concern. Tesla mandates a brake fluid test every 2 years, and a flush if the water content exceeds 2%. Do not use DOT 5 (silicone-based) fluid, as it is incompatible with the Model S ABS and stability control system. DOT 5.1 is technically compatible with DOT 4, but stick to a high-quality, name-brand DOT 4 to guarantee factory-level viscosity for the automated emergency braking systems.

Windshield Washer Fluid

Type and Spec: Any standard windshield washer fluid is acceptable. Intervals and Pitfalls: If you live in a cold climate, ensure you are using a winter-grade fluid rated for well below freezing. The Model S relies heavily on its forward-facing cameras located behind the windshield for its Autopilot and Full Self-Driving (FSD) features. If the washer fluid freezes and you cannot clear dirt or salt from the glass, these advanced driver-assistance systems will automatically disable themselves.

Missing Fluids: Engine Oil, Power Steering, and DEF

As an ASE tech used to traditional ICE (Internal Combustion Engine) vehicles, you might instinctively look for a dipstick or a power steering reservoir.

• Engine Oil: There is no internal combustion engine, hence zero API SP or GM dexos1 Gen3 engine oil is required.
• Power Steering Fluid: The 2021 Model S utilizes an advanced Electronic Power Steering (EPS) rack. An electric motor provides the steering assist, meaning there is no hydraulic pump, no lines to leak, and no fluid to flush.
• DEF (Diesel Exhaust Fluid): There is no diesel engine, hence no API CK-4 oil or ISO 22241 DEF required.

Always remember to place the vehicle in "Tow Mode" or power down the high-voltage system appropriately before performing under-vehicle fluid services. The high-voltage system requires immense respect and specialized training.

Find a trusted shop on Repairius.