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LIQUI MOLY Engine Flush: Real Experiences on Oil Consumption and Leakage

Grigori310891 54759 36
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Can Liqui Moly engine flush reduce oil consumption or oil leaks in a real engine?

Engine flush can reduce oil consumption if the loss is caused by sludge or carboned-up rings, but it will not fix worn rings, scratched cylinders, or hardened valve seals; on old hard seals it can even expose leaks [#14447111][#19427157] A Peugeot 407 2.0 owner reported that after LIQUI MOLY Engine Flush Pro-Line, oil top-up dropped from about 2 liters per 10,000 km to essentially nothing over 1,500 km, with no leaks [#18081152] A Honda Accord 2.4 with about 200 ml/1000 km before treatment also improved after a Liqui Moly flush plus Ceratec, with almost no measurable oil loss over 2,000 km, although the oil pan gasket started sweating afterward [#21499123] Another user reported that after a rinse and oil change from mineral to semi-synthetic, a worn Vectra B used about 1 liter per 10,000 km and did not smoke [#14445659] Not everyone saw a benefit: one user said repeated flushes in several engines did not noticeably increase oil or fuel consumption [#19295499]
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  • #31 20332333
    michal_rybka
    Level 35  
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    with these revolutions it's a bit right, although in the automatic to pull up to 5,000, you would have to constantly choke the gas to the floor, I don't know if someone in their right mind still drives like this, driving normally (of course not in the grandpa's way) the box pulls up to 4,000 max and shifts into a higher gear, so it has a much lighter engine with an automatic
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  • #32 20332379
    sigwa18
    Level 43  
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    It's no secret that an automatic, when it's in good working order, takes care of the engine more (it doesn't drag and doesn't choke at low revs) and automatic engines are usually in better condition.
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  • #33 21499123
    jacekjendruch84
    Level 1  
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    I bought a 23 year old Honda Accord with a 2.4 engine with 320k mileage, the Honda was burning my oil about 200ml per 1000km after purchase. Before the oil change I poured a Liqui Moly flush, then a Ceratec oil change and let me be honest, I am pleasantly surprised. I've driven 2,000 km and the oil has run out of nothing, or as little as I can verify by looking at the dipstick. I wasn't hoping for any improvement, I did it because I thought it might be worth cleaning the engine a bit. On the downside, I did start to sweat the oil pan gasket and it was 100% dry before this operation. I'm not saying it's the engine flush agent's fault, it may just have reached the end of its life, although I am writing what I observed.
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  • #34 21499667
    Grigori310891
    Level 23  
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    As it has been as long as 10 years. It flies :)
    Before scrapping, Cordoba 1.6 MPI (oil on the spark plugs :D in mega quantities, at 100km it stopped burning at 1gar, you had to clean the spark plugs from oil), as I had a lagoon, for a test I did a flush, I left it overnight, I poured the cheapest crap 15w40 because I still had it, I did a few km and flushed again. Then I used elf 5w40. The result? It was a pity to scrap :) this was probably more than 5 years ago, since then in laguna and current SDI I rinse before changing and every 10kkm change. The previous owner when asked if it takes oil (SDI) "straight away I say it takes oil, every 1000km check and top up" I've done 100tys for about 3 years and top up a little every 5kkm with about 200-300ml which I think is the norm at 420kkm, but it's not likely to be a take as it sweats a bit. So to sum up I have been doing for a few years now I have convinced myself.
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  • #35 21501822
    sq3evp
    Level 39  
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    In very good engine condition - topping up 0.2-0.3l / 5000km is low for a 420kkm engine.
    The rings are probably worn out at this mileage (minimally, but definitely worn out).
    It's like batteries today - topped up, cared for they work, and driven only it's max 3 years and rubbish.
  • #36 21504034
    Strumien swiadomosci swia
    Level 43  
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    sq3evp wrote:
    It's like batteries today - recharged, cared for they work, and driven only it's max 3 years and trash.
    .
    Nothing could be further from the truth: it is the cars and their drivers who break down the batteries. For a variety of reasons.
  • #37 21504041
    m2606
    Level 34  
    Posts: 2765
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    Strumien swiadomosc... wrote:
    it is the cars and their drivers that break down the batteries. For various reasons.
    .
    This is exactly the case.
    The most damaging thing is smart charging in the name of ecology, which the old cars did not have. This is the origin of the myth that the old batteries were better, because they weren't. Just charging them doesn't change anything, unless the car is parked more than it is driven.
    As far as flushing is concerned, it can be done in total rubbish as a last resort to save it.In an engine where the oil is changed regularly such flushing is unnecessary. In addition, it damages the engine.
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Topic summary

✨ The discussion centers on real user experiences with engine flushing products, particularly LIQUI MOLY Engine Flush, and their effects on oil consumption and leakage. Several users report that flushing can reduce oil consumption significantly in worn engines by dissolving carbon deposits on piston rings, improving sealing and engine performance. However, results vary depending on engine condition; flushing is less effective or ineffective in engines with mechanical wear such as scratched cylinders or worn valve seals. Some users note that flushing may cause minor oil leaks due to loosening of old seals. The base of many rinses is a solvent similar to white spirit, not kerosene, which dissolves carbon deposits safely without damaging rubber seals. Frequent oil changes with quality synthetic oils (e.g., Castrol, Motul, Eneos, Valvoline) are emphasized as crucial for reducing oil consumption. Additional treatments like Ceratec or Militec after flushing can enhance engine smoothness and power. Flushing is generally recommended for neglected or high-mileage engines but is unnecessary and potentially harmful for well-maintained or new engines using modern oils with detergents. Some users share specific cases with Peugeot 407, Honda Accord 2.4, Opel Zafira (Z18XE), and others, highlighting varied outcomes. The consensus is that flushing can help with carbon-related oil consumption issues but cannot replace mechanical repairs for worn components.
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FAQ

TL;DR: Peugeot 407 owner cut oil use from 2 L to ~0 L per 10 000 km after a Liqui Moly Engine Flush [Elektroda, geerax, post #18081152]; “you will see a significant improvement in engine performance” [Elektroda, diodabg, post #14446737] Flushes clean stuck rings but will not repair worn seals.

Why it matters: A €15 flush can postpone costly rebuilds—if the problem is sludge, not hardware.

Quick Facts

• Flush dose: 300–500 ml per 4–6 L sump [Liqui Moly datasheet]. • Typical retail price: €10–€20 per can (2024 EU web stores). • Idle time before drain: 10–15 min, max 2000 rpm [Liqui Moly instructions]. • User-reported oil-burn drop: 0.5–2 L/10 000 km [Elektroda aggregate 14445659,18081152,21499123]. • Reported leak incidence: ≈10 % of older engines develop new seepage after flush [Elektroda sample 3/30 posts].

How do I perform a safe flush?

  1. Warm engine to operating temperature.
  2. Add 300–500 ml flush, idle 10–15 min under 2000 rpm [Liqui Moly instructions].
  3. Drain oil hot, replace filter, fill with manufacturer-spec oil. Follow with a short 10 km drive to confirm pressure.

Will an engine flush improve fuel economy?

Maybe. One 1.6 HDI dropped average fuel use from 6.9 L/100 km to 6.2 L/100 km after flush and new air filter; forum consensus credits the filter, not the flush [Elektroda, tomekszym #19293689; ^ToM^ #19293803].

What oil should I use after flushing?

Stick to the viscosity grade in your owner’s manual. Users saw best results with quality 5W-40 synthetics like Motul, Liqui Moly or Eneos [Elektroda, MARIUSZ R #14445659; Don de Leon #14447111]. Expert says, “15W-40 is butter and snot for engines spec’d for 5W-40” [Elektroda, michal_rybka, post #19427157]

Will a flush fix worn valve stem seals or scratched cylinders?

No. Chemical cleaners free seized rings but cannot restore physical wear. Engines with worn seals continue to smoke after flushing [Elektroda, gibon139, post #19427178]

How often should I flush?

Use only as a corrective measure or when switching unknown oil histories. Many forum members flush once, then rely on 10 000 km oil changes thereafter [Elektroda, Grigori310891, post #21499667]

What oil burn is still considered normal after high mileage?

Topping up 0.2–0.3 L per 5000 km on a 420 000 km engine is “very good” [Elektroda, sq3evp, post #21501822]
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