Liqui Moly Pro-Line Engine Flush comes in a 500 ml can, the regular Engine Flush in 300 ml. Every measurable figure the manufacturer publishes is the same for both. What differs is the dose: 100 ml per litre of oil against 50 ml per litre. That is why Liqui Moly Pro-Line is cheaper per millilitre and more expensive per flush. Both are true at once.
Last updated: 23 August 2026. Expanded with a cost per 100 ml breakdown and a same-market comparison of the safety data sheets.
Liqui Moly Pro-Line or the regular Liqui Moly Engine Flush 2640: what actually differs
Can size and recommended dose. Everything else, as far as the manufacturer’s own documents go, looks the same.
Liqui Moly (100% owned by the Würth Group) sells its oil system flush in two lines. The regular Engine Flush is part number 2640 in a 300 ml can. Liqui Moly Pro-Line Engine Flush, or Liqui Moly Pro-Line Motorspülung in German, is a 500 ml can sold as 2427, 2662 and 2037. Those three numbers are the same product in the same size, differing only in the label language. There is more on the company itself in our Liqui Moly brand profile.
“Liqui Moly Pro-Line” is this manufacturer’s workshop range. A driver looks at the shelf, sees two cans of the same brand with one priced higher, and concludes the expensive one must be chemically stronger. The documents point somewhere else.
| Liqui Moly Engine Flush 2640 | Liqui Moly Pro-Line Engine Flush 2427 | |
|---|---|---|
| Part number | 2640 (Polish market) | 2427, 2662, 2037 |
| Retail size | 300 ml, and only 300 ml | 500 ml, and only 500 ml |
| Larger formats | 50 l and 205 l drums | 1 l, 5 l, 20 l, 50 l |
| Dose per the manufacturer | 300 ml for up to 6 l of oil 50 ml per litre | 500 ml for up to 5 l of oil 100 ml per litre |
| Running time | about 10 minutes at idle | 10-15 minutes at idle |
| Price per can (Poland, August 2026) | 27.39 PLN - 62.57 PLN | 38.31 PLN - 55.00 PLN |
| Price per 100 ml | 9.13 PLN - 20.86 PLN | 7.66 PLN - 11.00 PLN |
Prices checked on 23 August 2026 on the Polish price comparison site Ceneo (product cards 7582938, 26703428, 33071398, 125003878) and at the retailer melox.pl. These are Polish retail prices and they will look different in other countries. They also move from week to week and vary between shops, so treat the range as a reference point rather than a price list.
Where the claim about a 300 ml Liqui Moly Pro-Line comes from
A claim circulates online that Liqui Moly Pro-Line Engine Flush is a 300 ml pack selling for 30-45 PLN. No such pack exists.
The official Liqui Moly Pro-Line Engine Flush product sheet lists ten pack variants: six 500 ml versions with different label languages, then 1 l, 5 l, 20 l and 50 l canisters. A 300 ml can appears nowhere on that list, in any language, on any market. The 30-45 PLN band does fit the regular Liqui Moly Engine Flush 2640 rather well, and that one genuinely is 300 ml.
It looks like two true facts glued into one false sentence. The size and price of the smaller can, attached to the name of the more expensive line. The consequence for a buyer is concrete: you walk into a shop with 40 PLN budgeted for Liqui Moly Pro-Line, see 47 PLN or 55 PLN, and assume the seller is gouging you. He is not. There is 200 ml more liquid in the can.
The mirror image is worth knowing too. You cannot buy the regular Engine Flush in 500 ml. Retail is 300 ml only, and above that the manufacturer jumps straight to 50 l and 205 l drums, which is a format for workshops and distributors rather than for a driver.
Cost per millilitre and cost per flush
These are two different sums and they point opposite ways. Liqui Moly Pro-Line is cheaper per millilitre. It is more expensive per engine flushed. Both results are correct, and the gap between them is worth understanding.
Per millilitre the arithmetic is easy. The cheapest Liqui Moly Pro-Line offer found was 38.31 PLN for 500 ml, which is 7.66 PLN per 100 ml. The cheapest regular 2640 was 27.39 PLN for 300 ml, which is 9.13 PLN per 100 ml. The dearer can has the cheaper millilitre, by roughly 16 percent.
Except you do not buy millilitres for their own sake. You buy them to flush a specific engine, and that is where the dose comes in. For 2640 the manufacturer specifies one 300 ml can for up to 6 litres of oil. For Liqui Moly Pro-Line, one 500 ml can for up to 5 litres. That is 50 ml per litre against 100 ml per litre, so twice the concentration in the sump.
| Engine holding 5 litres of oil | Liqui Moly Engine Flush 2640 | Liqui Moly Pro-Line Engine Flush 2427 |
|---|---|---|
| What you need | one 300 ml can | one 500 ml can |
| Concentration in the oil | 50 ml per litre | 100 ml per litre |
| Cost of the job (example price) | about 30 PLN | about 47 PLN |
| Cost per litre of oil treated | 6.00 PLN | 9.40 PLN |
That works out at 1.57 times more for the same job on the same engine. You are paying for a stronger bath, not for a different shelf price.
There is a third sum almost nobody runs, and it beats both of the above. The same 300 ml can, the same part number, sells in Polish shops for anything from 27.39 PLN to 62.57 PLN. That is 35.18 PLN of spread on one product, 2.3 times dearer at the worst place. No choice between Liqui Moly Pro-Line and 2640 comes close to that. Where you buy moves this bill more than which variant you pick.
Section 3 next to section 3: what the safety data sheets show
The same hydrocarbon base and the same two functional additives in identical concentration bands. The lists are not character-for-character identical, though, and we are not going to pretend otherwise.
One note on method before the numbers. We compare sheets from the same market, the European ones, because that is the only comparison that means anything. Australian and American editions of the same product are written under different rules, carry different lists and different H statements, so mixing them with European sheets manufactures differences that are not there. The 2640 sheet is the Polish edition, version 0037 of 1 November 2021. The Liqui Moly Pro-Line sheet is the German edition, version 0039 of 9 August 2024.
| Section 3 entry | Liqui Moly Engine Flush 2640 PL sheet 0037 (01.11.2021) | Liqui Moly Pro-Line Engine Flush 2427 DE sheet 0039 (09.08.2024) |
|---|---|---|
| Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cycloalkanes, under 2% aromatics (EC 918-481-9) | 70-90% | 75-90% |
| Distillates (petroleum), hydrotreated light paraffinic (CAS 64742-55-8) | not listed | 0-5% |
| Distillates (petroleum), hydrotreated heavy paraffinic (CAS 64742-54-7) | 0-5% | 0-5% |
| White mineral oil (CAS 8042-47-5) | not listed | 0-5% |
| Distillates, solvent-dewaxed heavy paraffinic (CAS 64742-65-0) | 0-5% | 0-5% |
| Distillates, solvent-dewaxed light paraffinic (CAS 64742-56-9) | 0-5% | 0-5% |
| ZDDP, zinc dialkyldithiophosphate (CAS 68442-22-8, EC 270-478-5) | 1-2.5% | 1-2.5% |
| Calcium alkylbenzenesulfonate (CAS 722503-68-6, EC 682-816-2) | 1-2.5% | 1-2.5% |
| Mixture classification | Patrz karta produktu | Patrz karta produktu |
| Number of section 3 entries | 6 | 8 |
Check the sheets yourself: Liqui Moly Engine Flush 2640, version 0037, Polish edition and Liqui Moly Pro-Line Engine Flush, version 0039, German edition. We break the second one down separately on the Liqui Moly Pro-Line safety data sheet page.
What follows from this, and what does not. The newer sheet lists eight entries, the older one six. The surplus is two extra fractions of highly refined base oil, each in the 0-5% band. The base in Liqui Moly Pro-Line starts at 75% instead of 70%. Nearly three years sit between the two documents, and section 3 does get expanded at later revisions, sometimes with no change to the liquid at all. Whether that is what happened here, the documents will not tell you. What is certain: both functional additives carry identical CAS numbers and identical concentration bands, and the mixture classification matches exactly.
Neither additive is there by accident. ZDDP builds an anti-wear layer on sliding pairs, and the calcium sulfonate holds loosened dirt in suspension so it leaves with the old oil instead of settling back down. During a flush the oil runs thinned by solvent, so both jobs matter at that moment. For how other manufacturers handle this, see our database of engine flush safety data sheets, where we lay out section 3 for 340 products.
Technical data: where the sheets agree and where the manufacturer says otherwise
The product sheets for both give the same figures. Exactly the same.
- Flash point: 63 °C for both.
- Pour point: -45 °C for both.
- Viscosity: below 7 mm²/s for both.
- Same fluid colour and the same GHS classification.
This is where it stops fitting one neat story. The FAQ on the official LIQUI MOLY POLSKA shop states that the products differ in pack size and in the concentration of the flushing substance. Safety data sheets give concentration bands rather than exact figures, and product sheets do not give a formulation at all. Which means precisely this: neither “it is the same liquid in two cans” nor “these are two different formulations” can be proven from the available documents.
The honest reading is this. Every measurable physical figure the manufacturer publishes is identical for both. The difference in strength that the manufacturer’s own shop describes is fully accounted for by the dose alone, 100 millilitres per litre of oil instead of 50. You do not need to assume a different formulation to explain a stronger bath, because double the concentration explains it on its own. Whether anything else separates them in the can stays an open question, and that is how we are leaving it.
Is the Liqui Moly Pro-Line premium worth paying
In a few situations yes, though rarely for the reason people reach for it.
A big sump. At 7-8 litres of oil you need more product anyway, and one 500 ml can beats two smaller ones. This is the most practical reason on the list.
A workshop. A garage doing several oil changes a day buys from the professional range for logistics. Hence the 5 l and 20 l canisters in that line, which the consumer version does not have.
Deliberately choosing the higher concentration. If you want a stronger bath, Liqui Moly Pro-Line hands it to you directly instead of making you work out two cans.
When there is no point paying more: an ordinary oil change on a well-kept engine holding 4-5 litres. The regular 2640 will do there what the manufacturer describes it doing, and you keep some money for the filter. And the filter gets changed with every flush, because all that loosened deposit heads straight for the element. The manufacturer calls for changing it along with the oil in both cases.
One more caveat from the Liqui Moly Pro-Line product sheet: do not use it in motorbikes with a wet clutch. Liqui Moly sells a separate product for motorcycles.
What about Liqui Moly Oil Sludge Flush 5200
Different product, different job, and it replaces neither of the two above.
The 5200 sheet, version 0025 of 8 May 2026, shows a completely different make-up. The hydrocarbon base drops to 20-40 percent and 2-butoxyethanol appears at 10-20 percent, a polar solvent from the glycol ether family. The calcium detergent gets a wider band at 1-10 percent, ZDDP stays at 1-2.5 percent.
The way it is used explains that make-up. This one goes in ahead of the planned oil change and you drive a distance with it, rather than idling for a quarter of an hour. You cannot drive around with seventy percent light solvent in the sump, because the oil film would not survive it. So there is half as much solvent here and the polar glycol ether does the work over the longer distance. If your oil change is an hour away, this product will not have time to do what it was designed for. We did not check 5200 prices for this update.
What a safety data sheet will not tell you
Which flush cleans your engine better. A safety data sheet classifies hazards and lists dangerous ingredients above a disclosure threshold. It does not measure cleaning power, it does not measure how much deposit came out, and it does not measure wear protection.
Two things follow that are easy to forget when reading a table like the one above. A similar list does not prove similar effectiveness, because effectiveness is settled by testing rather than by a safety document. And the reverse: a substance missing from section 3 is not necessarily missing from the product, because the disclosure duty covers classified ingredients above a threshold, so an unclassified additive or one held as a trade secret legitimately never appears on the sheet.
So everything written here about composition describes documents, not how either product behaves in an engine. If you want a comparison wider than a single brand, we collected one in our engine flush ranking and comparison. And if you are choosing between brands rather than within one, we have a separate TEC 2000 and Liqui Moly comparison.
FAQ
Does Liqui Moly Pro-Line Engine Flush come in 300 ml?
No. The official product sheet lists ten pack variants: six 500 ml versions in different label languages, plus 1 l, 5 l, 20 l and 50 l canisters. There is no 300 ml can on that list. The 300 ml pack is the regular Engine Flush, part 2640 on the Polish market.
What is the difference between Liqui Moly 2427, 2662 and 2037?
Nothing beyond the label language. It is the same Liqui Moly Pro-Line Engine Flush in the same 500 ml can, sold under three numbers for different markets.
How does Liqui Moly Pro-Line differ from the regular Engine Flush?
Size and dose. Liqui Moly Pro-Line is 500 ml for up to 5 litres of oil, which is 100 ml per litre. The regular 2640 is 300 ml for up to 6 litres, which is 50 ml per litre. The technical figures on the product sheets are the same for both: flash point 63 °C, pour point -45 °C, viscosity below 7 mm²/s.
Which one works out cheaper?
Depends what you are counting. Per 100 ml of liquid Liqui Moly Pro-Line wins: 7.66-11.00 PLN against 9.13-20.86 PLN for the 2640, on Polish prices checked 23 August 2026. Per flush of an engine holding 5 litres the 2640 wins, because it is dosed at half the concentration.
How much Liqui Moly Pro-Line goes into how much oil?
The manufacturer specifies one 500 ml can for up to 5 litres of engine oil and 10-15 minutes at idle, depending on how dirty the engine is. Follow the instructions on the can you actually bought, because shop listings are often imprecise.
Do the safety data sheets prove it is the same liquid?
They do not, and they cannot. They show the same base and the same two functional additives in identical concentration bands, but a band is not an exact concentration. On top of that, the manufacturer’s own shop FAQ says the products differ in the concentration of the flushing substance. The available documents will not settle this either way.
Can I buy the regular Engine Flush in 500 ml?
Not at retail. The regular Engine Flush comes in 300 ml, and above that the manufacturer offers only 50 l and 205 l drums. If you want 500 ml of Liqui Moly in one can, that variant is Liqui Moly Pro-Line.
Does the oil filter have to be changed after a flush?
Yes, and it is part of the job rather than an option. A flush loosens deposit that then circulates in the oil and ends up in the filter element. The manufacturer calls for changing the filter together with the oil in both cases.
Sources
- Safety data sheet, Liqui Moly Engine Flush, part 2640, version 0037 of 01.11.2021, Polish edition (document 10417).
- Safety data sheet, Liqui Moly Pro-Line Engine Flush, version 0039 of 09.08.2024, German edition (document 10414).
- Safety data sheet, Liqui Moly Oil Sludge Flush, part 5200, version 0025 of 08.05.2026, Polish edition (document 10345).
- Liqui Moly product information sheets for Engine Flush and Liqui Moly Pro-Line Engine Flush: pack list, dosage, flash point, pour point, viscosity.
- FAQ of the official LIQUI MOLY POLSKA shop, section on differences between the flush variants.
- Retail prices: Ceneo price comparison, product cards 7582938, 26703428, 33071398 and 125003878, and the retailer melox.pl.
Prices were checked on 23 August 2026, come from the Polish market and are given as ranges, because they move week to week and differ between shops. If the manufacturer issues a newer revision of any sheet, the composition data here may diverge from the current document. Always check the sheet that belongs to the can you are actually buying.
