Fluid Flushes Are Often Just Used by Auto Repair Facilities to Flush Your Wallet

Though mechanics may tell you otherwise, fluid flashes are almost always unnecessary and can do more harm than good

The Truth Behind Automotive Fluid Flushes
Image: NCCC
October 10, 2018

Ever stroll into a dealer or auto shop and see the pamphlets and brochures scattered across the counter advertising fluid flushes designed to save your engine, transmission or other critical vehicle system? Perhaps you've seen a stand set up in the corner with a vial of clear fluid on one side and a vial of dark fluid on the other?

Most consumers don't realize that fluid loses its original color very quickly as the coloring is added to help distinguish between the varying types of fluid.

To Flush or Not To Flush?

Let's face it. We're going to be inundated with proposals by shop personnel to have our fluid flushed instead of the traditional drain-and-fill. Do you really need a fluid flush? In most cases, no. To automotive shops, the flush is a money-maker. A majority of the cost billed is labor, so it's a very lucrative business.

"In a majority of cases, the average driver doesn't need any of the expensive fluid flushes," says Ed, an ASE certified Master Technician with 31 years of experience working on everything from motorcycles to tractor trailers and super movers. "Automotive fluid is designed to go through the extreme. The rule book is full of recommendations to change the fluid since fluid does in fact break down. The rule book doesn't say anything about flushing."

Financial Incentives

The personnel checking you in are often rewarded with financial incentives to get you to agree to the service. They'll throw every line in the book your way in order to get you to buy the service.

But regardless of what they say, a fluid flush will never fix a broken seal, will never fix a malfunctioning sensor, will never repair a slipping transmission, and will never restore vitality to worn components.

"The only way to do that is to replace the part," continues Ed. "Replacing the part is a very effective solution to any problem provided, of course, that the part is faulty. I've seen customers get bombarded with sales pitches, but I always pull the owner to the side and give the real story about what is likely wrong and what certainly will not work. My customers always ask for me to work on their cars because I tell them that these solutions don't work."

So what should consumers do when faced with this dilemma?

What to Do

"Follow your maintenance schedule. The maintenance recommended by your manufacturer is usually the only maintenance you will need aside from other components that simply fail due to age or wear," Ed recommends. "The engine won't perform any better by having every last trace of old engine oil flushed out. If you want to flush all the old oil out, do a second oil change a few minutes after you do the first one. It basically does the same thing for a fraction of the money. But it seems like a waste to me."

Should consumers ever perform a fluid flush? Ed points out that many of the aftermarket machines use harsh chemicals to clean the fluid passageways that often damage seals and sensors. Several manufacturers, including General Motors, have begun advising technicians never to use these machines as they have been shown to damage components and that damage caused will not be covered under warranty.

Although there are some circumstances where a flush should be performed--such as after a component suffers a catastrophic failure or becomes contaminated--flushes are not recommended as part of regular maintenance. Even if the chemicals used don't damage sensors and other components, they can dislodge buildup that may be sitting in an out-of-the-way place and force it into tiny passageways, thereby cutting off the flow of oil. Think of it as a piece of plaque in an artery that dislodges and finds its way into the brain.

"If the brake system gets contaminated with dirt or water or if the transmission fails and sends metal particles into the lines, of course we will flush it as those contaminants negatively affect performance and can cause repeat failures," says Ed. "Even then, I only use the same type of fluid as is coming out, never any additional chemicals."

Flushes and Sludge Buildup

What about a component, such as an engine, that has a lot of sludge buildup? Would any flush help it?

"If your engine is full of sludge, there are worse problems you must first consider other than cleaning it out. Sludge indicates neglect. At that point, engine replacement is my usual recommendation as the cost to disassemble and clean is usually more than replacement," Ed says. "You have to also consider all the small passageways and valleys inside the engine through which oil can flow. Many newer vehicle use engine hydraulics to control valve timing, which can easily plug up with lose debris floating through the system causing more problems."

In short, the only service consumers will ever need is the service prescribed in the maintenance schedule. We always advise consumers to avoid shops that aggressively upsell "extras," such as these fluid flushes.

We should just start calling them "wallet flushes."