Top 7 Best Engine Flushes
By | Last updated: May 4, 2021
enigne flush

We’ll preface this post with the admonition that, unless you’re reasonably familiar with the environs of an engine bay, you should keep your paws off stuff like this. However, a case can be made that anyone who’s fleet is comprised of machines that actually need these products is probably intimately familiar with the contents of a rusty toolbox.

On one hand, additives like these have their proponents, who declare them the best thing to happen to cars since the assembly line. On the other, there is a group of skeptics who feel they’re nothing more than snake oil in a can. All we can tell you is that there are plenty of them on the market and it’s our job to suss out a few with the best reviews. And, for the love of all that’s holy, read the instructions with products like this.

Given the hooptie state of our cars around here, we may have even used one or two of these things ourselves.

1. Editor's Choice: Liqui Moly Pro-Line Engine Flush

If you’ve ever watched any sort of racing out of Australia, you’ve seen plenty of ads for Liqui Moly. Despite their massive presence Down Under, they’re actually a German brand with roots stretching all the way back to the 1950s. Their sole purpose for being is to hawk oils, lubricants, and additives.

Of which this is the latter, naturally. It’s an engine flush marketed as an easy way to clean and flush the oil systems of gasoline or diesel mills. Neutral to seals and other materials installed in the engine, it purports to give a ‘gentle and rapid cleaning’ by dissolving sludge and lacquer while isolating solid particles and liquid contaminants.

Pros/This brand makes over 4,000 products so they know their stuff, top-notch reviews
Cons/You'll probably end up buying more than one item from them
Bottom Line/Solidly endorsed by real-world customers

2. Rislone 100QR Engine Treatment Conditioner and Cleaner

Like the Turtle Wax name we mentioned the other day, Rislone is a brand your author associates with products his father used. This is not wholly a bad thing, since each of Dad’s cars lasted well over 10 years. Well, except the 1984 Renault Encore. Because Kenosha.

This bottle of wonder is apparently capable of freeing valves and lifters, something that afflicted Dad’s 1978 Blazer from just about Day 1. The fact it kept running could be a testament to Rislone. The company also says this product maintains oil viscosity while dissolving and removing harmful deposits.

Pros/Been around forever
Cons/Best to buy a case of six (small bottles)
Bottom Line/If it was good enough for a tired 305 small block...

3. Golden Touch Fast Flush Engine Flush

We’ll leave inappropriate and lewd comments about the brand name of this engine flush to the side since this editorial team is far beyond making such jokes. Actually, we aren’t – but VerticalScope’s lawyers are tired of cleaning up our messes. You won’t be cleaning up a mess with this stuff either, since it’s a petroleum-based product that is free of kerosene.

Made in America, it is said to quickly remove more engine sludge and deposits than a conventional oil change. Note well: it’s good for gasoline engines, not diesels. The instructions say to drain existing oil and change the filter. Add a gallon of this product and install a clean filter. After running the engine for 5 minutes, drain the works of it out and replace the filter again. Refill the engine with approved motor oil and you’re on your way.

Pros/Has 'for professional use' printed right on the label
Cons/lulz at the brand name
Bottom Line/A big ol' jug of golden touch

4. WYNNS Engine Flush - Petrol and Diesel

The word ‘petrol’ in this product’s title is a dead giveaway as to the brand’s origin. But here’s the thing: engines don’t really seem to care what country you’re in, unless it’s a former Bloc country which generally has twigs in its gasoline supply.

Like others on this list, the Wynn’s product is promoted as able to quickly and efficiently dissolve varnish while removing sludge and other contaminants from vital engine parts. This should leave your car’s engine with sparkling clean internals – certainly cleaner than your internals after a feed of British grub.

Pros/Good for diesels or gassers
Cons/Very small can
Bottom Line/Add prior to an oil change for best results

5. CRC Salt Terminator Engine Flush

Yes, yes – this stuff isn’t technically in the same category as everything else on this list. It is, however, an engine flush … just one of a different type. Besides, we’re sure one or two of the nutty readers in our audience has a boat they use on the water.

This gear is an essential motor flush for marine engines that are operated in both saltwater and freshwater environments. It dissolves salt and leaves a protective coating to inhibit corrosion. A good many reviewers also report using it as a spray-on their boat trailers and the like to ward off the rust monster.

Pros/Chases away the rusties, has the word 'terminator' in its name
Cons/Not actually for yer car
Bottom Line/Captain's choice - or at least First Mate's

6. Marvel Mystery Oil

And you thought that Mystery Machine was the only thing with that name associated with Marvel (hold your vitriol-laced comments; we know it’s actually Hanna-Barbera). Here we have a two-pack of additive that is said to clean and lubricate your car’s fuel delivery system including carburetors.

According to the ad copy, this stuff reduces varnish and gum while preventing further build-up of the same. Valve stick and clatter should cease, while the car’s engine oil should not break down in extreme temperature conditions. It probably does bust sludge as advertised but we’d cast a skeptical eye at the claims of increased MPG.

Pros/Dump and run, easy to keep aboard the car
Cons/Your mileage may vary (literally)
Bottom Line/Worth a shot for 10 bucks

7. Energy Release Motor Flush

While the name of this brand might make one think it competes with the likes of Monster and Red Bull, it’s actually an engine flush similar to the majority of other items on this list. It, too, promotes itself as able to dissolve sludge and wash away its buildup. Again, we’ll question the claims of improved fuel economy unless we try it for ourselves.

Showing up in a simple can, Energy Release calls its product an anti-friction agent whose job it is to protect and condition metal surfaces during the cleaning process. After application, Energy Release says one should expect reduced friction of engine internals and increased performance.

Pros/Cheaper than the dirt in your car's engine
Cons/Relative lack of reviews
Bottom Line/Vast majority of reviews are full of praise

From time to time, TTAC will highlight automotive products we think may be of interest to our community. Plus, posts like this help to keep the lights on around here. Learn more about how this works.

(Editor’s note: This post is meant to both help you be an informed shopper for automotive products but also to pay for our ‘90s sedan shopping habits operating expenses. Some of you don’t find these posts fun, but they help pay for Junkyard Finds, Rare Rides, Rental Reviews, and whatever else. Thanks for reading.)

[Main Photo Credit: Phanu D Pongvanit/ Product images provided by the manufacturer.]

20 Comments on “Best Engine Flushes: Feeling Flushed...”

  • avatar

    I’ve heard some positive feedback about Marvel Mystery Oil in relation to flathead engines.

    I would probably not use any of these things on any engine designed after about 2005, although I guess if it is either try this or go to the junkyard, might as well try this.

    • 0 avatar

      Modern engines don’t need any of this stuff if you use good quality gasoline. I like Chevron when I can get it on the road.

      And as far as flushing the cooling system? I’ve never used anything but plain old distilled water, gallons and gallons of it, until it flushed clear.

      If you already tried that method then you know how much crud plain old distilled water will knock loose from your cooling system and heater core when you drive the vehicle until it gets up to operating temperature between flushes.

      It has taken me as much as three flushes to get the cooling system to drain clear in my vehicles.

      Best engine oil therapy? Change your oil often. That will keep the crud from building up.

      • 0 avatar

        You drive two decade old Toyota’s and not modern GM cars with Dex-Cool that is good for 150,000 miles.

        • 0 avatar

          NormSV650, there’s such a thing as aftermarket coolants like Zerex and other brands that are tailored to different factory specs, like HOAT, OAT, and NOAT anti-freeze, depending on the vehicle.

          I would not go the full 150,000 miles or 5 year replacement with any anti-freeze. It starts to break down and the waterpump lubrication become impaired because of the dirt inside the entire cooling system.

          The coolant in our 2012 Grand Cherokee, 2016 Tundra, and 2016 Sequoia had changed color after only three years of usage. Time to change.

          If you trust Dex-Cool to go the distance for you? Go head on!

        • 0 avatar

          Dex-Cool can do some awful things, like clog coolant passages in cylinder heads.

          • 0 avatar

            That’s what I had in mind when I wrote my comment. Know of one instance where Dex-Cool coagulated and clogged coolant passages.

            But the same can happen with Zerex, Prestone, etc. when they overheat or dissimilar metals of the cooling system dissolve into the coolant.

            The bottom line remains, change your fluids, and change them often. It’s not that hard to do.

            I’ve seen people in Southern California drain their coolant over a storm drain on the side of the road. I kid you not!

            Oil changes are a little more involved but nothing beats the detergent properties of fresh motor oil in an engine.

      • 0 avatar

        Incorrect, modern engines now more than ever need this with tiny oil passages used in Variable displacement, variable cam phasing and direct injection preventing fuel from doing it’s thing as a natural solvent on the heads, and to a (MUCH) lesser extent the cylinders.
        This is compounded by engine manufacturers claiming longer and longer oil change intervals using a oil designed to maximize the intervals, using a second blend to pass EPA regulations (usually a 0W-20) and then owners not being told to either change their oil more than once every 7,000 miles, and on top of that using the cheapest oil that their local oil change shop offers instead of something at least the same quality as the higher viscosity oil recommended for their engine.

  • avatar

    I had a 20 year old isuzu Rodeo that had some electrical gremlins it took me about a month to troubleshoot and fix. The fluid had all drained out of the transmission and when I drove it the first time I should have a waited a bit to let it circulate the fluid back through before driving it and it started slipping in first and second gear. I drained the fluid and added the Rislone stop slip additive when I filled it back up and it’s been about 5 years and 60k miles since and still no slipping. I was very impressed with the results.

  • avatar

    This nutty reader uses Salt-Away on his outboard. And yes calling it an engine-flush is a bit of a stretch… it just attempts to keep salt from building up in the blocks cooling passages. Saltwater kills everything over time. All the outboard mechanics I’ve dealt with swear by the stuff. My engine has survived for over 20 years with only one new head so it appears to be working I guess.

  • avatar

    My Dad used to use Marvel Mystery Oil in our 1951 Ford V-8. I wouldn’t put this stuff in anything newer.

  • avatar

    I actually do use the Marvel Mystery Oil (MMO), as well as Rislone products. MMO is basically a very good penetrating oil with some light cleaning ingredients. This is a long term use item, something that you’d mix with a fresh oil change, or put measured amounts in a gas tank over time. Works excellent in all engines I’ve used it in, but again- it absolutely takes time to work, I’m talking months of measured amounts each fill up at the pump or per OCI, depending on whether you’re using it in your gas or oil. I’ve used Rislone concentrate to clean up neglected engines, just run it in your choice of oil for approx 2500-3000 miles. Their newest product, Rislone-nano something or other, works great as well, but does take anywhere from 300-600 miles to notice the effect.

  • avatar

    “Flush” is not a word I generally associate with the vehicles under my stewardship. [Opinion: If you are proud of referring to your vehicles as “hoop***”, you should reevaluate your life choices. Step 1 in recovery: Go wash your vehicle by hand and pay attention to what you observe during the process.]

    Engine oil additives:
    – “Restore Engine Restorer & Lubricant” is on the ‘approved’ list for my fleet (currently six vehicles). As the last step of an oil change (using Mobil 1 Extended Performance High Mileage Formula), add the “Restore” to the crankcase with the engine running and *listen* to the engine. You’ll see.
    – “Lucas Oil Pure Synthetic Oil Stabilizer” is on the ‘currently under evaluation’ list. My kid is driving home from Texas right now and I have a PCV valve waiting for his vehicle and plan to add some of the Lucas additive from the gallon I ordered. Depending on how that turns out, will likely add Lucas to my mowers, and any vehicles with an oil consumption problem which haven’t responded to the Restore product.

    • 0 avatar

      Shake the bottle of Restore very well before adding it (can you read instructions? lol).

      If you are capable of shaking the bottle, you can use the “V8” size bottle in two 4-cylinders. Fortunately only one of my vehicles has 4 cylinders (one small-block Chevy [nods knowingly], one fake V8 [Northstar, here temporarily], three V6’s [frowns at the Mopar] and an I4 [good news: it’s a non-sludging Toyota]. The only one which burns oil is the 2006 Malibu (3.5L V6).

  • avatar

    The best mechanic I ever had told me there’s no need to use a flush treatment for cooling systems: clean water will do, as highdesertcat recommends. One flush alone doesn’t get the job done.

    He also said a normal engine doesn’t need a flush if proper oil changes are made, though he’s run a thinner viscosity oil for 500 easy miles or so on some engines that were doing heavy duty work (towing, hot weather, altitude driving).

    As far as transmissions were concerned, he said they should NEVER be flushed, just drained and refilled at proper intervals, including much shorter intervals when the vehicle is used for towing, hot weather, etc. That applies to both “standard” and automatics.

    Way back in olden times, before 1980, these products were okay for your engine/cooling system/transmission, and probably wouldn’t hurt on a high mileage vehicle built before 2000, except for gasoline additives. Adding anything to gasoline today risks damaging some expensive-to-replace emissions equipment.

  • avatar

    There is no such thing as a ‘good’ engine/transmission internal flush. They all have kerosene in them which swells the rubber seals, stopping leakage. The problem is, the seals never stop swelling, causing them to wear much faster. Such products are made to squeeze another 3000 miles out of a deathtrap that should have been scrapped years ago.

    • 0 avatar

      You’re right, as far as older cars are concerned, but with ethanol, a solvent, added to gasoline, automakers have had to replace a lot of internals to withstand the solvent. You can probably get away with some gas additives on flex fuel vehicles that can handle 85% ethanol. It’s still questionable whether the additive or its combustion products are compatible with some of the emissions equipment.

      • 0 avatar

        After Ethyl and Methyl, MTBE was the answer. Until it wasn’t. So Ethanol seemed to be the least harmful. Until it wasn’t.

        A few years back we spent ~6 months in Brazil at the invitation of my nephew and all the vehicles there run on “Alco’ol” fermented from sugar cane plus other plants.

        You can go a lot farther on a liter of good old gasoline, and with less internal wear and tear on seals, fuel lines, etc.

  • avatar

    Matthew, you must be a young whipper snapper, if you’re not familiar with Wynn’s products, and Marvel Mystery Oil.

    Since time immemorial (or so it seems), MMO (an “upper engine lubricant”) has been the go-to for engines that have sat for long periods of time, where there’s some question of whether they will crank or are seized. You typically pour or squirt a little in the cylinders (through the spark plug holes), and let them sit overnight before first turning them over by hand, then cranking.

    And Wynn’s Products was a drag racing sponsor back in the ’60s and ’70s, including being the title sponsor for Don Garlits’ “Wynns Charger” Top Fuel dragsters.

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