Prices verified Aug 2 · Always confirm at the retailer before buying.
Quick answer
Liqui Moly Pro-Line Engine Flush B00CR3RXTO and Liqui Moly Engine Flush Plus B071P7SJM6 are both pre-oil-change cleaners, but their useful differences are dosage, oil capacity, and vehicle-use boundaries. The current US registry lists Pro-Line at $22.00 with 4.7 stars from 9,681 reviews and Engine Flush Plus at $51.49 with 4.5 stars from 697 reviews. Liqui Moly's US Pro-Line page says one 500 ml can treats 3–5 liters of oil, the engine idles for 10–15 minutes, and the oil and filter are then changed; it also says the product is not suitable for motorbikes. The Engine Flush Plus product page says 300 ml treats up to 6 liters, the engine idles for about 10 minutes, and the oil and filter are then changed; it excludes motorcycles with wet clutches. These are manufacturer instructions, not independent proof of deposit removal, compression, oil consumption, wear reduction, or engine life. Check the vehicle manual and exact label before use.
Choose by vehicle, oil capacity, and label first. Pro-Line costs less and treats 3–5 liters with 500 ml; Engine Flush Plus treats up to 6 liters with 300 ml. Neither rating or manufacturer claim is an independent engine-performance test.
Mubboo Verdict
Best for most people
Liqui Moly Pro-Line Engine Flush
It is $29.49 lower in the current US registry and its US product page clearly states the 500 ml dose, 3–5 liter oil range, and pre-change procedure for compatible 4-stroke vehicles.
Pick the Liqui Moly Engine Flush Plus instead if
- Your compatible vehicle has up to 6 liters of oil and the 300 ml Engine Flush Plus dose matches its label.
- You prefer the Engine Flush Plus application instructions and have verified the vehicle maker allows this type of pre-change cleaner.
- You are not using either product on a motorcycle with a wet clutch.
- You understand that the higher price does not prove better cleaning or engine protection.
Liqui Moly Pro-Line Engine Flush vs Liqui Moly Engine Flush Plus, side by side
Liqui Moly Pro-Line Engine Flush
Pros:
- Current registry price is $29.49 lower
- US product page gives a 500 ml dose for 3–5 liters of oil
- US product page lists use with 4-stroke gasoline and diesel engines
Cons (honest weight):
- US product page says it is not suitable for motorbikes
- Manufacturer use instructions do not prove independent cleaning or engine-life results
- 500 ml dose and 10–15 minute idle procedure must match the vehicle and current label
Liqui Moly Engine Flush Plus
Pros:
- Current product page specifies 300 ml for up to 6 liters of oil
- Current product page specifies about 10 minutes of idling before the oil change
- Product page lists gasoline and diesel engine use
Cons (honest weight):
- Current registry price is $29.49 higher
- Product page says it is not suitable for motorcycles with wet clutches
- Manufacturer claims do not prove independent cleaning, wear, or engine-life results
Where each one wins
8 dimensions scored head-to-head. Liqui Moly takes 3; Liqui Moly takes 0.
| Dimension | Liqui Moly Pro-Line Engine Flush | Liqui Moly Engine Flush Plus | Winner |
|---|---|---|---|
| Current registry pricePro-Line is $29.49 lower in the current registry; prices can change. | $22.00 | $51.49 | Liqui Moly |
| Current ratingPro-Line has the higher current marketplace rating, which is not an engine test. | 4.7 stars | 4.5 stars | Liqui Moly |
| Dose and oil capacityThe vehicle's oil capacity and exact label determine which dose fits; do not substitute one procedure for the other. | 500 ml for 3–5 L | 300 ml for up to 6 L | Tie |
| Application timeBoth are added before an oil and filter change; follow the current product label. | 10–15 minutes idle | About 10 minutes idle | Tie |
| Vehicle fitCheck the vehicle maker, engine type, clutch arrangement, and product label. | 4-stroke gasoline and diesel; not motorbikes | Gasoline and diesel; not wet-clutch motorcycles | Tie |
| Current review volumeReview volume is marketplace context, not proof of deposit removal or engine life. | 9,681 reviews | 697 reviews | Liqui Moly |
| Change procedureNeither product is a leave-in replacement for engine oil; retain the specified drain and filter change. | Warm oil, idle, change oil and filter | Operating-temperature oil, idle, change oil and filter | Tie |
| Evidence boundaryManufacturer descriptions and ratings do not establish independent cleaning, compression, oil-consumption, wear, or engine-life results. | No Mubboo engine test | No Mubboo engine test | Tie |
| Overall | 3 wins | 0 wins | Liqui Moly |
Vehicle and Clutch Fit Come First
Check the vehicle manual and exact product label before comparing prices. Liqui Moly's US Pro-Line page lists 4-stroke gasoline and diesel engines but says the product is not suitable for motorbikes. Engine Flush Plus lists gasoline and diesel engines and says it is not suitable for motorcycles with wet clutches. Do not infer compatibility from the word engine flush.
Dose and Oil Capacity
Pro-Line uses 500 ml for 3–5 liters of motor oil, while Engine Flush Plus uses 300 ml for up to 6 liters. The quantities are product-specific. Do not pour one product at the other product's dose, exceed the label, or treat a broad oil-capacity range as approval for every engine.
Application and Oil Change
Both products are pre-change cleaners, not leave-in engine oil. Pro-Line's US instructions call for adding it to warm engine oil, idling for 10–15 minutes, and then changing the oil and filter. Engine Flush Plus says to add it at operating temperature, idle for about 10 minutes, and then change the oil and filter. Use the current label, the vehicle manual, and the correct oil and filter procedure.
What the Evidence Does Not Prove
Neither marketplace rating nor manufacturer wording proves a controlled improvement in engine performance. This page does not report independent testing of deposit removal, compression, oil consumption, wear, oil pressure, emissions, chain or belt durability, or engine life. A flush product also cannot diagnose a leak, blocked pickup, worn component, or oil-pressure fault.
Safety and Handling
Read the current label and safety data sheet before handling these chemical products. Liqui Moly's US Pro-Line safety data identifies a combustible liquid, serious eye irritation, possible allergic skin reaction, and aspiration hazard. Keep it away from heat and ignition sources, avoid breathing mist, use appropriate protective equipment, and follow disposal and first-aid instructions. Engine Flush Plus carries its own current label and SDS; do not transfer Pro-Line warnings to it or assume the two products have identical hazards.
Current Alternatives Are Different Flush Types
Other products in the broad flush category may target different systems. Four Seasons Super Flush Solvent is an automotive A/C flush solvent, and Star Brite Salt Off is a marine engine flush kit. They are not direct substitutes for an oil-system engine flush. Confirm the system, vehicle, fluid, and manufacturer instructions before buying.
Which should you buy?
| Your situation | Pick | Why |
|---|---|---|
| Compatible 4-stroke vehicle, 3–5 L oil, lower price matters | Liqui Moly Pro-Line Engine Flush | Pro-Line is $29.49 lower and its US page states the 500 ml/3–5 liter procedure. |
| Compatible gasoline or diesel vehicle, up to 6 L oil, 300 ml dose matches | Liqui Moly Engine Flush Plus | Engine Flush Plus states a 300 ml dose for up to 6 liters and about 10 minutes of idling. |
| Motorcycle or wet-clutch application | Liqui Moly Pro-Line Engine Flush | Do not choose either from this comparison; the reviewed manufacturer pages include motorcycle exclusions. |
| Known oil-pressure, leak, sludge, or mechanical fault | Liqui Moly Pro-Line Engine Flush | Do not use an additive as a diagnosis; follow the vehicle service manual or consult a qualified mechanic. |
| Need independent proof of cleaning, wear reduction, or longer engine life | Liqui Moly Pro-Line Engine Flush | Neither product is supported here by a controlled Mubboo engine test. |
| Need an A/C or marine cooling-system flush instead of an oil-system cleaner | Liqui Moly Pro-Line Engine Flush | Neither primary product is the right system type; use the vehicle or equipment maker's exact flush procedure. |
Pro-Line is $29.49 lower and its US page states the 500 ml/3–5 liter procedure.
Engine Flush Plus states a 300 ml dose for up to 6 liters and about 10 minutes of idling.
Do not choose either from this comparison; the reviewed manufacturer pages include motorcycle exclusions.
Do not use an additive as a diagnosis; follow the vehicle service manual or consult a qualified mechanic.
Neither product is supported here by a controlled Mubboo engine test.
Neither primary product is the right system type; use the vehicle or equipment maker's exact flush procedure.
What if neither is right?
Four Seasons Super Flush Solvent
$21.48
An automotive A/C flush solvent in the broad category; not a substitute for an engine-oil flush.
Star Brite Salt Off Marine Engine Flush Kit
$22.31
A marine cooling-system flush kit; not a substitute for an engine-oil flush additive.
Frequently Asked Questions
Liqui Moly Pro-Line vs Engine Flush Plus: which should I buy?
Check the vehicle manual, engine type, clutch arrangement, oil capacity, and exact label first. Pro-Line is the lower-price choice for a compatible 4-stroke vehicle whose 500 ml dose for 3–5 liters fits. Engine Flush Plus fits a compatible gasoline or diesel vehicle when its 300 ml dose for up to 6 liters fits. Neither is for the excluded motorcycle uses described by the manufacturer.
Is Engine Flush Plus worth $29.49 more than Pro-Line?
Only if its 300 ml dose for up to 6 liters and vehicle-specific instructions fit your application. The current registry price gap does not establish better cleaning, wear reduction, or engine life.
Can I use Pro-Line or Engine Flush Plus in a motorcycle?
The reviewed Liqui Moly pages include motorcycle exclusions: the US Pro-Line page says not suitable for motorbikes, and Engine Flush Plus says not suitable for motorcycles with wet clutches. Check the motorcycle and product makers before using any engine flush.
How long do I idle the engine with each product?
Liqui Moly's US Pro-Line page says 10–15 minutes, depending on contamination. Engine Flush Plus says about 10 minutes. Add each only at the stated oil temperature and then change the oil and filter as directed.
Will an engine flush fix oil pressure, sludge, leaks, or engine noise?
This comparison cannot promise that. A flush product is not a diagnosis or mechanical repair, and this page contains no controlled testing of oil pressure, sludge removal, noise, compression, or engine life. Follow the service manual or consult a qualified mechanic for a fault.
Are the products safe to handle?
Use the current label and SDS for the exact product. The US Pro-Line SDS identifies combustible-liquid, eye-irritation, skin-sensitization, and aspiration hazards and says to keep it away from heat and ignition sources. Use ventilation and protective equipment as directed and do not assume both products have identical hazards.
What are the current alternatives?
Four Seasons Super Flush Solvent is an automotive A/C flush solvent, while Star Brite Salt Off is a marine engine flush kit. They target different systems and are not direct substitutes for an oil-system engine flush.
How we compared. We used current US product-registry records for price, rating, review count, stock, and product images for the two primary ASINs and two current alternatives.
We checked the LIQUI MOLY US Pro-Line Engine Flush page, the LIQUI MOLY Engine Flush Plus page, and the US Pro-Line safety data sheet.
No Mubboo controlled engine, deposit-removal, compression, oil-consumption, wear, or engine-life test data is reported. Verify the vehicle manual, exact dose, current label, SDS, oil, filter, and system type before use.
Who wrote this and where's the data from?
Mubboo Editorial Team. Independent US-market consumer research. We separate current marketplace facts and manufacturer instructions from independent engine-performance evidence. This comparison is not a mechanical inspection or controlled engine test.