NHC MOTORS · SERVICE RECORD

Mercedes CLS400d: engine, transmission and brake fluids, each changed its own way

We changed the engine oil and filter, transmission fluid and brake fluid using methods suited to their respective systems. Cabin filters and tyre pressures were also addressed in the vehicle's service history.

BG brake fluid and the equipment used for the pulsed circuit clean and change

2018 Mercedes-Benz CLS400d

On this 2018 Mercedes-Benz CLS400d, we changed the engine oil and filter, transmission fluid and brake fluid. The transmission fluid was exchanged with dedicated equipment; the brake circuit received a pulsed clean before the fluid change.

Engine, transmission and brake fluid serve different systems and are changed by different methods. We checked temperature with a diagnostic tool during the transmission-fluid exchange and connected a hose at the wheel-side bleed point for the brake-fluid change.

01 / NHC MOTORS

We drained the engine oil and fitted a new filter

We collected the drained engine oil in a measuring container, fitted a new oil filter and used PETRONAS Syntium 5000 DM 5W-30. Replacing the filter with the oil removes the material caught by the old filter rather than leaving it in place for the fresh oil.

Collecting the used oil makes it possible to compare the amount with earlier fill and top-up records at a later service. Diesel oil darkens quickly, so colour alone is not a useful verdict; the change history and signs of leakage matter too.

Used engine oil collected in a measuring container

New oil filter fitted with the engine-oil change

PETRONAS Syntium 5000 DM 5W-30 used for the engine-oil change

02 / NHC MOTORS

We cleaned the brake circuit and changed the fluid

We connected BG PF7 equipment for a pulsed clean of the brake circuit, then changed to BG brake fluid. A hose at the wheel-side bleed point allowed old fluid to leave from the far end of the circuit, beyond the reservoir.

Brake fluid transmits pedal force to the wheel brakes and absorbs moisture over time. A full reservoir does not mean that old fluid is absent from the lines. A fluid change carries fresh fluid through the circuit; the pulsed process helps move old fluid and contamination out.

Brake-fluid replacement does not decide when pads or discs need replacing. Their wear and condition have to be assessed separately.

Hose connected at the wheel-side bleed point to remove old fluid from the circuit

03 / NHC MOTORS

The transmission fluid was exchanged with a dedicated machine

We connected BG PXT equipment at the transmission and used FUCHS TITAN ATF 9034 for a circulating exchange. The machine replaces outgoing fluid with fresh fluid, changing more of the fluid in the unit than a simple drain. We watched the flow through its sight window and read transmission-oil temperature on the diagnostic tool during the work.

Fluid volume changes with temperature, so each transmission has a specified temperature range for checking the level. This photo shows a temperature reading of 42°C during the work. The level-check temperature must follow the requirements for that transmission.

Transmission fluid differs from engine oil in both product and procedure. Earlier service information helps determine the right product and time for a future check.

FUCHS TITAN ATF 9034 used for the transmission-fluid exchange

Diagnostic screen showing 42°C during the work; this is a momentary reading

Transmission-fluid equipment connected beneath the car

Sight window of the transmission-fluid exchange machine

04 / NHC MOTORS

Cabin filters, top-ups and tyre pressures

We replaced both the recirculation-side and outside-air cabin filters. Changing only one leaves the other air path's filter in place.

Coolant and washer fluid were topped up, and tyre pressures were checked and adjusted. If coolant keeps falling after a top-up, the source of the loss needs to be investigated separately.

Engine oil, transmission fluid, brake fluid and filters have different service intervals. Looking at what has already been done helps decide what needs checking next.

Different fluid work on the CLS400d

Engine

PETRONAS 5000 DM 5W-30 and new oil filter

Transmission

FUCHS ATF 9034; 42°C shown during work

Brakes

BG brake fluid; wheel-side bleed hose

Other care

Cabin filters, coolant and washer top-ups

Container size is not the amount filled. The 42°C is the diagnostic temperature shown during transmission-fluid work.

Frequently asked questions

Does changing the engine oil also change the transmission fluid?

No. The engine and transmission use different fluids and are serviced separately. This CLS400d used PETRONAS Syntium 5000 DM 5W-30 for the engine and FUCHS TITAN ATF 9034 for the transmission.

Why check temperature during a transmission-fluid exchange?

Temperature changes the fluid's volume, so a level check follows a procedure and temperature range specific to the transmission. The 42°C shown during this job is a momentary display, not a universal target or proof of the final level.

Is topping up the brake-fluid reservoir enough?

A top-up restores the reservoir level; a fluid change replaces the old fluid in the circuit. On this car, BG PF7 equipment cleaned the circuit and a hose at the wheel-side bleed point let old fluid leave the system.

CLS400d fluid service, considered system by system

We check the engine, transmission and brake systems against the car's condition and past services. If shifting or pedal feel has changed, tell us when you book so we can discuss the relevant work.

We explain the work and estimate before proceeding with your consent.

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031-258-1617 · NHC Motors, Suwon · By appointment

Published 2026-09-26