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Fluid flush vs. drain and fill

For the past few years - mechanics have been offering fluid “flushes” (transmission flush, radiator flush etc) but I’ve heard that these flushes are actually bad for the car - stirring up particles at the bottom of the pans and putting them up through the various engine places.

I own a 2002 Toyota. Should I get my fluids “flushed” or drained. I understand that draining doesn’t remove all the old fluids - but I’m also not all that interested in getting a flush and have THAT cause problems.

Check your owner’s manual…regular fluid changes do not require flushes unless specifically indicated in the manual.

This is one of those topics where different folks have different strokes. Dagosa is right in my opinion, but other folks have different ideas. Some go for “fluid exchanges.”

I am one who from time to time, (which means 10,000 or 15,000 miles, not 50,000 miles, I drop three quarts and add back three quarts.

Others believe in dropping the pan and changing the filter, which I am told my Sienna does not have anyway.

I cannot say my choice is correct, my Sienna only has 164,000 miles on it. Ask me at 250,000 miles…

The most important thing, no matter which way you jump, is do not let that fluid get all messed up and cruddy. It doesn’t cost that much, especially if you do it yourself. I have heard figures on transmissions as high as $5,000 on a Toyota, though if mine blows, I will probably have it trucked to the border, and take it to a good tranny shop.

It is not cost effective to neglect the fluid.

Transmission fluid needs to be drained & replaced. Radiator flushes can’t hurt unless specified otherwise in operator’s manual. I don’t know why on earth you’d ever have your oil flushed (I don’t know what else could get pushed into “various engine places”), sounds like a $$$ flush to me.

If you have a V6 in your Toyota a motor flush might help if you have not been religious about your oil changes. The V6 motors have had “sludging” issues and the motor flush could help. If you’ve kept up with the oil changes every 5K miles likely no benefit. I haven’t heard anything about motor flushes causing damage.

Transmission flushes can cause damage if not done properly. Properly done, means drop the pan first and clean it and put in a clean filter, then do the flush. That is a few extra steps and many places (Quickie lube types) just hook up the machine and run the flush. This picks up debris from the pan and filter and circulates it where it can get into tiny holes and clutches and do more harm than good. To be safe, best to just drop the trans pan clean it, put in a new filter and refill to full with the proper fluid. This is other issue problem many places put in generic fluids. For your Toyota the Toyota brand fluid is the best bet.

Radiator flushes are fine and do no damage.

I’ve not heard of problems flushing out brake fluid, which should be done every 3 years if your Toyota has ABS brakes.

Recap: Motor no problem, only of benefit if you think your motor is dirty due to lax oil changes. Might be worth doing for a V6, or if you bought the car used.

Trans, avoid flushes due to frequent problems, drain and refill with new filter is best.

Radiator and cooling system, flushes are fine.

Brakes, flushes are fine.

Read your owner’s manual. If it is not there, don’t do it. The current rage for flushing every fluid in the car including the blinker fluid is nothing more than greedy business men trying to flush your wallet.

Most of these offers are a scam. The shops suggest fluid flushes for every customer who walks in the door. What they really want to do is flush your wallet.

I am not saying that these various flushes are always a bad idea; an older car may actually benefit by a brake flush or radiator flush after many years of service. A proper flush will not create new problems; it is merely an unnecessary operation intended to generate extra profit for the shop.

As others have said, read your owner’s manual. In most cases a drain and fill is all you need.

I’m of the belief that if the system fluids are exchanged as regular maintenance, those components in those systems last longer.

This is for those who don’t do their own vehicle maintenace service. Either because they don’t have the know-how or don’t care to do so.

Transmission fluid exchange. This exchanges all the old oxidized transmission fluid along with debris in the fluid that developes from normal transmission wear. Not exchanging all the fluid leaves this debris in the transmission, resulting in accelerated wear of the transmission.

Brake fluid flush. This removes the old contaminated brake fluid which prevents damage to brake components. Especially if the vehicle has ABS.

Power steering fluid exchange. This removes all the old oxidized power steering fluid along with the debris from the power steering system so that power steering pumps and rack and pinion assemblies last longer.

Coolant exchange. This removes all the old coolant that has depleted it’s additive packages for corrosion protection and lubrication.

I’ve found over the years, with manufacturers building system components out of lighter materials in order to save weight in the vehicles, these components aren’t as robust as in the past. And the #1 cause for component failure in these systems is the lack of fluid maintenance.


Fluids need changing because they become depleted of their additives, they become contaminated, they break down due to stresses (as in oil molecules), or they absorb moisture (as in some brake fluid). Draining and replacing fluids is important to compensate for these things. Flushing with chemicals does nothing to help this, and can remove protective coatings (like the silicates in coolant) that then need to be replenished again. They can even loosen accumulations that are better left intact.

I’m comfortable with flushing cooling systems out with hose water before refilling, but I do not believe in flushing with chemicals unless some known problem exists that the person is trying to resolve.

Opinions do vary on this subject. But the opinion of least integrity will IMHO come from one who stands to profit by the flushing. This is a revenue generator for many shops.

Thanks to everyone for their feedback. I do change all the fluids on my Rav (180,000 miles) regularly (every 50K or so) and it’s time again to go change them, but I’ve always struggled with the “to flush or not to flush” theory.