I have been driving in Singapore for about 20 years. Over the years, I have driven different types of cars — renewed COE cars, second-hand COE cars, used cars, and brand-new cars. Each type teaches you something different.
A brand-new car usually feels smooth, quiet, and responsive. But with used cars and COE cars, the experience can be very different. Sometimes the car feels sluggish. Sometimes the engine feels rough. Sometimes throttle response is not as sharp. Sometimes fuel consumption gets worse.
From my experience, this is not always because the car is "old". Many times, it is because the previous owner may not have maintained the car properly — delayed oil changes, wrong oil grade, ignored air filters, old spark plugs, dirty fuel systems, or carbon build-up.
After many years of driving, and now also seeing vehicles from a workshop perspective, I have learnt one important lesson:
A car does not stay smooth by accident. It stays smooth because it is maintained properly.
In this article, I will explain three LIQUI MOLY products and how they can be used properly as part of preventive car maintenance. They may look similar on the shelf, but they are not used the same way.
Why I Pay Attention to Additives
I want to be clear from the start: additives are not magic bottles.
They will not repair a worn engine, faulty injector, leaking gasket, clogged catalytic converter, bad sensor, or poor compression. If a car has a real mechanical or electrical fault, proper diagnosis and repair are still needed.
But when used correctly, quality additives can support preventive maintenance — especially in Singapore, where cars operate under hot weather, frequent idling, short trips, traffic jams, stop-start driving, and occasional long drives into Malaysia.
Additives should not be used to cover up poor maintenance. They should be used to support proper maintenance.
The Three LIQUI MOLY Products
LIQUI MOLY Engine Flush Plus
Engine Flush Plus is used to clean the inside of the engine oil system. One 300ml can is sufficient for up to 6 litres of oil. It is added to motor oil at operating temperature, the engine idles for approximately 10 minutes, then the old oil and oil filter are replaced.
For used cars and renewed COE cars, this makes sense when the oil-change history is uncertain. Over time, sludge and deposits can build up inside the oil circuit — especially if the previous owner delayed servicing or used the wrong oil grade.
Do not drive around with Engine Flush Plus inside the engine. It is meant to be drained out together with the old oil. Best handled during a proper workshop service.
LIQUI MOLY Injection Cleaner
Injection Cleaner is suitable for petrol fuel injection systems. One 300ml can is sufficient for up to 70 litres of fuel, is effective over 2,000km, and mixes spontaneously with fuel. For most Singapore passenger cars (40L–60L tanks), one can per full tank is appropriate.
It can help with starting difficulty, rough idle, poor throttle response, performance loss, and carbon deposits on intake valves and the combustion chamber. It is also tested safe for turbochargers and catalytic converters.
This can be useful for cars that feel mildly sluggish or have not had fuel-system cleaning for a long time — and as a periodic preventive step for higher-mileage petrol cars.
Injection Cleaner goes into the petrol tank — not into engine oil. If the car has worn spark plugs, injector failure, or sensor faults, Injection Cleaner will not replace proper diagnosis.
LIQUI MOLY Oil Additive
Oil Additive is different from the other two products. It is not an engine flush. It does not go into the petrol tank. It is an MoS₂-based anti-friction additive — the dosage is 5%, or 50ml per 1 litre of motor oil, and it can be added at any time after fresh oil is filled.
For a typical Singapore passenger car using 3.5L–5L of engine oil, the workshop must check the actual oil level after adding — the total level including the additive must not exceed the maximum dipstick mark.
For older engines, higher-mileage cars, or cars that spend a lot of time in hot traffic, I see this as an optional support product for smoother running and wear protection.
The Correct Sequence If Using All Three
- Add Engine Flush Plus into old engine oil
- Idle engine for approximately 10 minutes
- Drain old oil and replace oil filter
- Refill with fresh engine oil (correct grade)
- Add Oil Additive based on oil capacity — do not overfill
- Add Injection Cleaner into the petrol tank before refuelling
Engine Flush Plus — cleans before the oil change.
Oil Additive — protects through the engine oil.
Injection Cleaner — cleans through the petrol tank.
My Advice to Used-Car & COE-Car Owners
If you just bought a second-hand or renewed COE car, do not assume everything is fine just because the car can drive. A proper baseline service is important first. At minimum, check:
- Engine oil condition and level
- Air filter and cabin filter
- Spark plugs (especially for higher-mileage cars)
- Brake fluid and coolant condition
- Battery health (load test)
- Tyre condition and tread depth
- Basic OBD scan for fault codes
After that, additives can be considered as part of a proper maintenance plan — not as a substitute for knowing the car's actual condition.
Why I Bought These Products from Entrust Motorworks
I wanted to understand these products from both sides — as a long-time driver and from a workshop perspective. As a car lover, I believe owners should understand what they are putting into their cars. As a workshop supervisor, I also believe workshops should not just sell products.
A good workshop should explain:
- What the product does
- Where it goes
- When to use it
- How much to use
- What it can help with — and what it cannot fix
For used cars and renewed COE cars especially, where maintenance history may not always be clear, the wrong product used in the wrong place can create confusion. The right product, used at the right time, can support better long-term maintenance.
Final Thoughts
A smooth car is not only about the car brand. It is about how the car is maintained.
The right approach: Diagnose properly. Service properly. Use the correct oil. Replace what needs replacing. Then use additives as maintenance support.
That is how I would maintain my own car — and that is the advice I give to any careful driver who wants their car to stay smooth, reliable, and enjoyable for as long as possible.
Product usage information and technical details were referenced from LIQUI MOLY / LIQUI MOLY Singapore product information. This article combines those product facts with personal driving experience and workshop observations.
Not sure which product
is right for your car?
Speak to the team at Entrust Motorworks before using any additive. A proper check ensures the right product is used at the right time, in the right place, and in the right amount.