Flush or Not?

To flush or not to flush? Car fluids you should really replace.

corroded rad


Should you listen to your service department's recommendation on fluid replacement? That depends

“Yes, Mr. Smith, we have your appointment confirmed for the 15th at 8:30 a.m., in addition to the oil change service you’ve requested, we’ve noted from your vehicle’s history files that it’s also due for a brake and steering fluid flush as well as a transmission oil service. Can we schedule your appointment to accommodate those required services?”

If you haven’t heard this from your automotive service consultant more than a few times, well, you haven’t been to a manufacturer’s dealership, independent garage, or auto service chain outlet in the last decade or so. The growth in this auto service segment has been ballooning over the last 15 to 20 years. If you’re a diligent consumer, you’ll oftenbook an appointment refer to your vehicle’s owner’s manual or maintenance guide to learn more about these services, but you won’t find any information on flush/treatment preventative maintenance in those publications. No automaker recommends them. Or perhaps you’ll ask your service consultant for the low-down or maybe just say “no, thanks” or just go along with the suggestions and try not to wince when your oil change invoice balloons to several hundred dollars.

Some background may help to put things into perspective. Automakers, in a move to improve their market share, have leaned out their recommended service guides and stretched time and distance intervals to position their products in the “low-operation-costs” bracket. Improvements in materials and assembly for most mainstream vehicles have upped their reliability scale and this lends credence to the maker’s position. However, for all the advancements in late model technology and engineering, most of an average vehicle’s fluids haven’t evolved at the same rate.

different fluids

Dealership service departments were looking to expand their offerings as recent downturns in warranty and customer-pay repairs left them with spare capacity. They were also employing methods of retaining clients who might have moved to independent and chain shops after their relatively short automakers’ warranties expired. And they were pleased to be able to offer added value as several of the top treatment suppliers include extended auto component/system warranties to consumers who became regular users of their services. As the average Canadian vehicle owner operates his or her daily driver for a substantial amount of time and distance past manufacturer’s warranty coverage, being able to obtain a low price guarantee on some of the most expensive-to-repair components can be an attractive offer. Here’s a look at some of the most common “recommended” services.

Transmission flush services. Servicing an automatic transmission can be completed in two manners; removing the drain pan and replacing the fluid and filter or power flushing the fluid with specialized circulation equipment along with a filter replacement. Automakers only recommend the first method even though it only removes about half of the fluid. A great deal of the transmission’s fluid will remain in the torque convertor, and oil cooler and lines during a simple drain and refill process. A power flush will circulate all of the oil fluid out before pumping in new. The flush system will also remove more solid and metallic debris thus extending clutch plate and moving-component life. It also prevents oil cooler or line blockage. Carmakers recommend an auto transmission fluid change between 50,000 and 100,000 km on average.

Engine cooling system service. As many of today’s vehicles are using long-life or five- to 10-year coolant, its replacement interval has been substantially extended from what it was when ordinary green antifreeze was common. As with transmission fluid replacement, there are two main methods of replacement. And as with drain vs. power flush on transmissions, power flushing an engine’s cooling system will remove more of the old fluid and debris as well as introducing a water-pump lubricant into the system. Long life coolant service intervals are usually between 100,000 and 150,000 km for most makers and those still using the old-style green coolant should replace it around the 70,000 km mark. Individual manufacturer intervals may differ.

Brake fluid replacement. This fluid seldom has a recommended replacement interval with carmakers. The main concern that brake fluid replacement addresses is the reduction of the water content in the fluid. With age, water is introduced into brake lines and hoses via condensation on the steel portions of the lines and the cast metal parts of the wheel brake units. This accelerates corrosion leading to fluid leaks. One hidden benefit of this process is that every bleeder screw on the system must be opened to complete it therefore reducing the risk of them seizing with age leading to the replacement of a caliper or two down the road.

Power steering fluid service. This is another fluid that carmakers consider “lifetime” with no replacement recommendation. Power steering systems are rather simple in design with only engine bay heat and sub-zero winter temperatures to provide any extreme operating conditions. Flush treatment suppliers claim to reduce the risk of steering gear seals, pump and hose failures. Opting for a treatment supplier that provides a system warranty with purchase can help alleviate the often expensive and common repair costs of steering fluid leaks.

Fuel injection/intake service. There’s a multitude of opinions both pro and con on this service, only matched in numbers by the count of different treatment suppliers. Carmakers never recommend injector service or fuel system purges in their maintenance schedules. But many vehicles have been prone to carbon buildup on engine valves and varnish coatings on throttle plates. The two main reasons can be grouped into poor fuel quality and low-speed vehicle operation or stop/start driving on short trips. Repair shops can accurately predict the demand for this service based on fuel price increases. As the cost of fuel goes up, the weight of the driver’s gas foot gets considerably lighter. When high-efficiency engines, designed to run at higher RPMs are subjected to pokey driving and/or poor fuel, deposits will occur. A good quality fuel system cleaning treatment, when properly applied, can reduce these buildups.

Whether or not you say yes or no to your service consultant’s flush recommendations depends on several things. Are you planning on keeping the vehicle long enough to warrant some additional warranty coverage that certain treatment suppliers offer? Is this coverage worthwhile/cost effective? Do you have faith in your service provider’s experience and opinions? Are you a preventative maintenance or drive-it-until-it-drops type of vehicle owner? Do you agree that improved design, engineering, and construction of today’s autos make them less reliant on routine maintenance in our often extreme climates and road conditions?

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