About this item

• Product Overview

  AMSOIL Engine and Transmission Flush (FLSH) helps restore fuel economy, increase operating efficiency and reduce emissions in gasoline and diesel engines, and automatic transmissions. Its potent, detergent-based formula cleans sludge and deposit build-up, promoting reduced oil consumption. AMSOIL Engine and Transmission Flush is safe on parts and can be easily disposed of with waste oil.

  Restores Vehicles 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 air-borne 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.

  • Prepares engines and transmissions for new oil
  • Removes deposits and sludge for improved efficiency, fuel economy and lower emissions
  • Prolongs equipment life
  • Detergent-based formula is environmentally friendly
  • Compatible with seals and gaskets
  • One-treatment results
  • Easily disposed of with waste oil

  AMSOIL Engine and Transmission Flush Benefits
  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, it 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

  Applications
  AMSOIL Engine and Transmission Flush is recommended for diesel and gasoline engines, and automatic transmissions. Do not use it in 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 entire 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 entire 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.

  (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.

• Technical Specifications
  Data Bulletin

  Data Bulletins

  Warranty

  WARRANTY

  SDS

  SDS

  
  
  
• Product Reviews
  4.9 star rating

  Based on 256 reviews

  Based on 256 reviews

  See all customer reviews

  Sort by

  Most Recent Most Helpful Highest Rating Lowest Rating Oldest

  • 5 star rating
    Best Flush!
    By  BD,  a  Verified Buyer  from  Virginia  on  May 01, 2026

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    Amazing results with my 20 year old Nissan Xterra. Besides making the 4.0 run smoother it increased mileage by almost 2 mpg (highway). With the current cost of fuel anything that does that has earned me as a loyal customer.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Beatiful cleaner
    By  RICARDO,  a  Verified Buyer  from  Ottawa  on  April 28, 2026

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    Describe the issue

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    This product is very special; it cleans my engine without altering the oil's chemical composition, removing all the dirt that accumulates in my turbocharger. This renews the life of my engine every year.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    top notch product
    By  CHARLES,  a  Verified Buyer  from  spruce grove , alberta  on  April 27, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    used this a few times now, major difference in engine performance after using and new oil change, engine runs smother
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Why not
    By  LAWRENCE,  a  Verified Buyer  from  Camry  on  March 20, 2026

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    Seemed like a good idea at the time but I always use this before an Amsoil change
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Damn good engine flush
    By  RYAN,  a  Verified Buyer  from  Lookout mountain Georgia   on  March 16, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Have always used this product after engines or transmissions are broken in to flush and swap to amsoil. Its simple follow instructions and do a good warm complete drain and it will get stuff out of a engine or transmission you would never know existed. Typically after using product be it in a hydrostatic drive transmission or old diesel engine thats been on conventional after swapping over to amsoil it takes hundreds of hours or thousands of miles to not have to struggle to see oil on a dipstick because its that crystal clean.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Awesome Engine Flush
    By  CURTIS,  a  Verified Buyer  from  Texas   on  March 05, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    As long as you follow the instructions on the bottle then it makes a great engine flush. I have started using it with at least every other oil change.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Nissan Titan XD 5.0L Cummins Flush
    By  JOE,  a  Verified Buyer  from  Up Nort  on  February 18, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Awesome product! Flushed tons of soot out of my engine after truck going on a diet. I will be using it in my transmission soon.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Oil
    By  ALBERT,  a  Verified Buyer  from  PA  on  February 17, 2026

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    Great product, love recommending it.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 4 star rating
    Cleaner
    By  TODD,  a  Verified Buyer  on  February 13, 2026

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    Describe the issue

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    I would say it is definitely doing something based on the color change in the oil. Checked oil with dipstick made note of color ran the flush through color was darker on the dipstick. When drained the oil it was definitely darker in color, so the flush is definitely loosening up some stuff in the engine.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Safe and thorough if used as directed.
    By  CURTIS,  a  Verified Buyer  from  Taylor County Texas  on  February 12, 2026

    Open report issue form

    Describe the issue

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    Safe to use at every oil change, but you must follow the directions.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (1) NO (0)

• Highlights

  Prepares Engines and Transmissions For New Oil

  • Engineered for gasoline and diesel engines and automatic transmissions
  • Helps restore fuel economy, increase operating efficiency and reduce emissions
  • Potent, detergent-based formula cleans sludge and deposit build-up, promoting reduced oil consumption
• Returns

  We offer easy returns for customers. If your product is unused and unopened, you may return it within 30 days for a full refund of the purchase price. View full AMSOIL Return Policy.

• Payments

  We accept Visa, Mastercard, American Express, Discover and PayPal, and provide secure checkout and encrypted payment processing.

• Product Overview

  AMSOIL Engine and Transmission Flush (FLSH) helps restore fuel economy, increase operating efficiency and reduce emissions in gasoline and diesel engines, and automatic transmissions. Its potent, detergent-based formula cleans sludge and deposit build-up, promoting reduced oil consumption. AMSOIL Engine and Transmission Flush is safe on parts and can be easily disposed of with waste oil.

  Restores Vehicles 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 air-borne 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.

  • Prepares engines and transmissions for new oil
  • Removes deposits and sludge for improved efficiency, fuel economy and lower emissions
  • Prolongs equipment life
  • Detergent-based formula is environmentally friendly
  • Compatible with seals and gaskets
  • One-treatment results
  • Easily disposed of with waste oil

  AMSOIL Engine and Transmission Flush Benefits
  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, it 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

  Applications
  AMSOIL Engine and Transmission Flush is recommended for diesel and gasoline engines, and automatic transmissions. Do not use it in 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 entire 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 entire 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.

  (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.

• Technical Specifications
  Data Bulletin

  Data Bulletins

  Warranty

  WARRANTY

  SDS

  SDS

  
  
  
• Product Reviews
  4.9 star rating

  Based on 256 reviews

  Based on 256 reviews

  See all customer reviews

  Sort by

  Most Recent Most Helpful Highest Rating Lowest Rating Oldest

  • 5 star rating
    Best Flush!
    By  BD,  a  Verified Buyer  from  Virginia  on  May 01, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Amazing results with my 20 year old Nissan Xterra. Besides making the 4.0 run smoother it increased mileage by almost 2 mpg (highway). With the current cost of fuel anything that does that has earned me as a loyal customer.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Beatiful cleaner
    By  RICARDO,  a  Verified Buyer  from  Ottawa  on  April 28, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    This product is very special; it cleans my engine without altering the oil's chemical composition, removing all the dirt that accumulates in my turbocharger. This renews the life of my engine every year.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    top notch product
    By  CHARLES,  a  Verified Buyer  from  spruce grove , alberta  on  April 27, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    used this a few times now, major difference in engine performance after using and new oil change, engine runs smother
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Why not
    By  LAWRENCE,  a  Verified Buyer  from  Camry  on  March 20, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Seemed like a good idea at the time but I always use this before an Amsoil change
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Damn good engine flush
    By  RYAN,  a  Verified Buyer  from  Lookout mountain Georgia   on  March 16, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Have always used this product after engines or transmissions are broken in to flush and swap to amsoil. Its simple follow instructions and do a good warm complete drain and it will get stuff out of a engine or transmission you would never know existed. Typically after using product be it in a hydrostatic drive transmission or old diesel engine thats been on conventional after swapping over to amsoil it takes hundreds of hours or thousands of miles to not have to struggle to see oil on a dipstick because its that crystal clean.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Awesome Engine Flush
    By  CURTIS,  a  Verified Buyer  from  Texas   on  March 05, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    As long as you follow the instructions on the bottle then it makes a great engine flush. I have started using it with at least every other oil change.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Nissan Titan XD 5.0L Cummins Flush
    By  JOE,  a  Verified Buyer  from  Up Nort  on  February 18, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Awesome product! Flushed tons of soot out of my engine after truck going on a diet. I will be using it in my transmission soon.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Oil
    By  ALBERT,  a  Verified Buyer  from  PA  on  February 17, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Great product, love recommending it.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 4 star rating
    Cleaner
    By  TODD,  a  Verified Buyer  on  February 13, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    I would say it is definitely doing something based on the color change in the oil. Checked oil with dipstick made note of color ran the flush through color was darker on the dipstick. When drained the oil it was definitely darker in color, so the flush is definitely loosening up some stuff in the engine.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (0) NO (0)
  • 5 star rating
    Safe and thorough if used as directed.
    By  CURTIS,  a  Verified Buyer  from  Taylor County Texas  on  February 12, 2026

    Open report issue form

    Describe the issue

    Cancel Submit
    Safe to use at every oil change, but you must follow the directions.
    Bottom Line

    Yes, I would recommend this to a friend.
    Was this review helpful?

    YES (1) NO (0)