AMSOIL Engine & Transmission Flush

Engineered for both gasoline and diesel engines and automatic transmissions. Helps improve operating efficiency, increase fuel economy and reduce emissions.


Prepares Engines and Transmissions For New Oil – Works with any oil.

Many oils lose their detergent properties towards the end – revert back to a clean engine or transmission.

AMSOIL Engine and Transmission Flush (FLSH) helps restore fuel economy, increase operating efficiency and reduce emissions in gasoline and diesel engines. Engineered for both gasoline and diesel engines. Its potent, detergent-based formula cleans sludge and deposit build-up, promoting lower operating temperatures and reduced oil consumption. AMSOIL Engine and Transmission Flush is safe on parts and can be easily disposed of with waste oil. Unlike other brands this one is non flammable and does not contain solvents.

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Package sizes include:
16-oz. Bottle
16-oz. Bottles (case of 12)
5 Gallon Pail
55 Gallon Drum

Printable Product Data Sheet for AMSOIL Engine and Transmission Flush.

Vehicle Look-up: Match AMSOIL Products to your model

Helps Lower Temperatures. Latest in Flush Technology!

Restores Drivetrain Operation to Like New

New engines and transmissions run more efficiently, but over time they gather harmful deposits that cause power and performance loss. Stop-and-go driving, prolonged idling, short trips that do not allow the engine to reach full operating temperature, towing, the ingestion of airborne dirt, fuel dilution, water condensation and oxidized oil all can promote sludge build-up in motor oil and transmission fluid. As it settles, sludge clogs narrow oil passages, restricting oil flow to vital parts, especially the upper valve train area.

In transmissions, deposits can form on clutch plates, causing hesitation and erratic shifting. Ultimately clutch glazing can set in, reducing the life of the transmission. Deposits in engines and transmissions can accelerate wear, causing power loss and increased fuel consumption.

Here are some common uses:

  • Cleans engines and transmissions for improved efficiency, fuel economy and lower emissions
  • Cuts oil consumption (Webmaster comments: Surprised me even!)
  • Prolongs equipment life
  • Detergent-based formula more environmentally friendly – No danger of residual product left in engine or transmission.
  • Compatible with seals and gaskets
  • One-treatment results
  • Easily disposed of with waste oil

Although this product is marketed for Do-It-Yourself users, AMSOIL’s Engine & Transmission Flush offers advantages for service centers that use a flushing machine. The multi-use formulation and easy disposal of AMSOIL Engine & Transmission Flush make it more economical than the single purpose product they may be using that could require special disposal procedures.

Other suggested uses:

  • After an Antifreeze Leak
  • After Running Conventional Lubricants

Lengthen the life of the next oil change

Installing new oil or transmission fluid into a dirty vehicle may not be enough to remove deposits and increase efficiency. The detergents and dispersants in many lubricants may not be able to handle leftover sludge and deposits. You then have a situation where the new lubricant becomes unfit for service miles before the scheduled or recommended change interval. This condition accelerates the formation of even more harmful deposits.

From the TECH Department:

Unlike many flush products, AMSOIL Engine and Transmission Flush features a multi-use formulation that dissolves and disperses sludge, varnish and deposits in both engines and automatic transmissions. Due to its detergent-based formulation, used AMSOIL Flush can be easily disposed of with waste oil, making it more user-friendly. Its advanced formula of light base oil technology, powerful detergents and dispersants provides safe cleaning action.
AMSOIL Engine and Transmission Flush  is compatible with both petroleum and synthetic oils, preparing poorly maintained equipment for installation of new oil. It represents the first step toward restoring neglected equipment to top-notch performance. AMSOIL Engine and Transmission Flush provides the following benefits in only one treatment:

Gasoline and Diesel Engines

  • Helps loosen sticky valves and rings, minimizing blow-by and reducing emissions
  • Helps quiet lifter noise
  • Promotes lower operating temperatures through sludge removal
  • Easy Disposal

Automatic Transmissions

  • Cleans deposits in oil cooler and ports
  • Helps unclog fluid passages
  • Cleans deposits and varnish from clutch plates, helping improve efficiency
  • Promotes smoother operation and transmission life through reduced shift delay


AMSOIL Engine and Transmission Flush is recommended for diesel and gasoline engines, and automatic transmissions. It is not recommended for CVT transmissions or differentials.

Directions for Use

Though it works in one treatment, AMSOIL Engine and Transmission Flush is safe enough to be used at every oil change. If using a flushing machine, follow the manufacturer’s recommendation. Otherwise, use the following guidelines:

Engine: Add 16 oz. bottle of AMSOIL Engine and Transmission Flush to engine oil fill port. Idle the engine for 10-15 minutes, then immediately drain the oil. Ensure enough time for the system to completely
drain. Remove and replace the engine oil filter. Refill engine with new engine oil in the viscosity grade recommended by the manufacturer.

Transmission: Engage emergency brake. Add 16 oz. bottle of AMSOIL Engine and Transmission Flush to transmission oil fill port. Idle for 10-15 minutes; shift through drive and reverse. Do NOT place vehicle under heavy load. Drain entire transmission and torque converter of fluid. FILTER MUST BE CHANGED prior to refilling with new transmission fluid.

NOTE: It is not recommended to flush transmissions that do not have a removable pan or access to the transmission filter.

Treat Rates for Larger Sumps

Sump Size

up to 10 quarts – Use 1-bottle
10-20 quarts – Use 2 bottles
20-30 quarts – 3 bottles
30-40 quarts (7.5 to 10 gallons) – 4 bottles

More Advice – “How to change Transmission Fluid Yourself” – Tech Service Document

(above) Automatic transmission clutch plates pre-cleanup. Varnish and glazing is heavy on some of the plates.
(above) Automatic transmission clutch plates after cleanup with AMSOIL Engine and Transmission Flush reveal lighter glazing and varnish.
(above) Cylinder head pre-cleanup. Note the sludge deposits on and around the valve springs and push rod openings.
(above) Cylinder head after cleanup with AMSOIL Engine and Transmission Flush. The valve springs and push rod openings are noticeably cleaner, with fewer sludge deposits. The manufacturer’s stamping is more easily seen.

What is an engine flush?

An engine flush is an aftermarket chemical additive designed to clean accumulated deposits, sludge and other gunk from your engine. You pour it into your engine’s oil-filler port and idle the engine for about 10-15 minutes. It mixes with the oil and circulates through the engine, helping dissolve sludge and clean deposits. Then, you drain the oil (along with much of the gunk, in theory), change the oil filter, add fresh oil and return to the business of driving.

The tiny openings in the oil pickup tube screen can easily plug with sludge, starving the engine of oil.
The tiny openings in the oil pickup tube screen can easily plug with sludge starving the engine of oil

Deposits and sludge can form for several reasons, including frequent short trips that don’t allow the oil to fully warm up and evaporate moisture, the ingestion of air-borne dirt, fuel dilution and high heat breaking down the oil. As it settles, sludge can clog narrow oil passages or the screen on the oil pickup tube, restricting oil flow to vital parts, especially the upper valve train. Deposits can cause the rings to stick, reducing engine compression and horsepower.

Is an engine flush necessary?

A good engine flush can help loosen deposits and dissolve sludge, returning your engine to like-new condition. However, in old engines with high miles, sludge may be the only barrier keeping oil from seeping through worn or cracked seals. Removing the sludge exposes the seals for what they really are – junk. Soon, your engine begins leaking oil, and you’re mind instantly associates the engine flush product with an oil leak.

In reality, the seals were already bad; the flush simply revealed their true condition.

If you suspect your vehicle falls into this camp, leave well enough alone and skip the engine flush. It’s probably not worth trying to revive an engine in such poor condition without first fixing the bad seals or other defects. In effect, you’re choosing your problem: either sludge and deposits robbing performance or, if you clean the engine, the seals showing their true condition.

Part of a good maintenance regime

But that’s not to say an engine flush is never a good idea. In fact, it’s often the first step in helping restore a neglected vehicle to top-notch performance. And, often when you buy a used vehicle, that’s what you’re getting – a vehicle whose owner found antiquing on Saturday afternoon more enjoyable than changing oil or dropping the transmission pan. Consequently, your “pre-owned” ride, while not complete junk, may boast a sketchy maintenance record.

In these cases, a potent, detergent-based flush can help prepare the engine for new oil, loosening sticky valves or rings and helping remove harmful sludge. While not a required step when switching to AMSOIL synthetic motor oil, we do recommend flushing your engine if you want to give your vehicle a fresh start.

Some people also claim an engine flush will free large chunks and cause an avalanche of debris to clog passages inside your engine. Don’t worry. AMSOIL Engine and Transmission Flush cleans at the molecular level, ensuring the deposits are dissolved and properly exit the engine with the oil when it is drained. This helps the new oil get off to a “clean start” and perform to its engineered capacity.

How deposits and sludge form

If it did its job, your engine’s performance will return to the heady days of its youth, when it delivered maximum power and efficiency. Over time, however, harmful deposits and sludge may have accumulated, causing power and performance loss.

Why do we promote the AMSOIL Engine Flush?

Well first off let me explain there is no truth to the myth that you must use our or any flush to switch to synthetic oil. One reason this is false is because AMSOIL products are engineered to be completely compatible with non-synthetics.

The AMSOIL flush is primarily needed so that you get the most out of our engine oils. Any vehicle with over 20,000 miles will likely have oil deposits to some degree. The level of deposits could depend on the quality of oil used, stop and go driving, high mileage, idling, poor air filtration, if the motor is turbocharged, the use of conventional motor oils or synthetics lacking a decent detergent additives, etc.

These deposits create an acidic condition which reduces the life of any oil’s TBN or ability to neutralize acids. When this happens, wear results.
AMSOIL’s engine flush will start working right away on this condition allowing the new oil change to last longer and do more work in reducing deposits and keeping chemicals and wear components in suspension. AMSOIL’s engine flush is a necessary step in reducing operating costs. Because it’s a detergent based product and not solvent based, the risk of any wear in both engine and transmission is eliminated.

Basically the AMSOIL engine & transmission flush contains the same type of detergent additive which is in our proprietary blends anyway, so any residue will not contaminate the the oil at all. The technology of these current detergents are beyond what was available only a couple years prior.

Here is part of an article from AMSOIL’s Tech Guide on Acids as being one of three parts which destroy a motor oil:

Too Acidic
Acids are a normal by-product of burning fossil fuels. Different fuel types, engines and combustion conditions create varying levels of acid formation. These acids, transferred via blow-by gases, are carried away to the engine oil. Oils are designed with a detergent that neutralizes these acids before they accumulate and cause engine damage. The detergent level is measured with a test called Total Base Number (TBN). This measure of alkalinity drops over the life of the oil and reaches a critical level when the oil can no longer consume the acids created by combustion. When TBN reaches a critical level,
acids build up quickly and attack the surfaces most susceptible, including yellow metals and lead-lined bearings. Without correction, this condition quickly worsens and results in excessive chemical wear. Although less common, this failure mode can cause significant damage if left uncorrected.

AMSOIL synthetic motor oils are formulated to provide a broad level of overall protection, evidenced by guaranteed extended drain intervals. Synthetic base oils help resist oxidative decomposition, and a properly balanced, high-quality additive package helps keep contaminants in check and engines running for a long time.

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