Engine oil is the most commonly changed fluid, and most people understand you need to change your oil. But why does it need to be changed? Engine oil contains a number of chemical additives that help it keep the inside of the engine clean. It also prevents sludge formation, and maintains viscosity, among other things. The basic oil itself doesn’t “wear out”, but the chemical additive package does.
Another factor that plays into oil change intervals is dilution. As you drive your car, the engine oil absorbs acids, combustion gases, and unburned gasoline. Draining and replacing the oil is the only way to eliminate these contaminants. Sometimes just draining the oil and replacing the filter isn’t enough to get all the sludge out of the engine. In these cases, your mechanic can run the engine with a special cleaning solvent in the oil before draining it. If necessary, he can hook the oil system to a machine that does a more aggressive job.
A short note on fully synthetic oils is appropriate here. Full synthetics give the best possible protection to your engine, almost eliminating friction wear. Full synthetic oil is more expensive than conventional oil or the synthetic blend that our basic oil change comes with. But the payoff is in longer service life. You can also extend your change intervals, but the big difference is in the level of protection your engine gets.
As I mentioned, most people understand the importance of oil changes. I’ve always thought it curious that not everyone grasps the reality that all automotive fluids have finite life-spans. I’ve put together some info on a few other fluids for you to cogitate on. One quick comment on fluids. If you wait until you can see that a given fluid is dirty, you’ve already done some damage by waiting too long. It’s like waiting until you smell like rotting roadkill to bathe. Don’t wait to shower until people tell you that you need to shower!
Braking systems use hydraulic fluid to transmit the motion of the brake pedal to a brake on each wheel of the car. Brake fluid must stick to specific requirements. For example, brake systems get very hot, so the fluid needs to tolerate extreme temperatures without boiling or deteriorating. Also, brake fluid must not react adversely with any of the materials used in brake components such as calipers, hoses, and anti-lock brake circuitry.
Manufacturers recommend flushing brake fluid every two years to restore depleted chemicals and flush out moisture, particulate contamination, and copper contamination. Moisture is absorbed from the atmosphere, and copper and particulate contamination come from the action of the braking system itself. The only way to thoroughly and safely flush a modern brake system is with a machine that forces fresh clean fluid through the entire system and each wheel’s individual brake until all traces of old dirty fluid are gone.
Coolant is the same thing as anti-freeze. It’s the fluid that takes the heat generated by the combustion process and friction in your engine and transmits it to the atmosphere using the radiator. It also transfers some of that heat into the passenger compartment when you turn the heater on.
Coolant and Freon, or refrigerant, are not the same thing. Refrigerant is what your A/C system uses. Coolant transfers heat efficiently, keep your seals and gaskets in good shape, and minimize electrolytic action in your engine, radiator, heater core, and other cooling system components.
Over time, the chemicals in the coolant become depleted and contaminants accumulate in it. It requires a thorough cleaning and power flush to bring the system back up to proper condition. The best type of service circulates a cleaning and neutralizing chemical, then reverse-flushes the entire system with fresh coolant until all traces of contamination are gone.
Automatic Transmission Fluid
Automatic transmission fluid has several roles to fill. It serves as a lubricant, a hydraulic fluid, a coolant for the transmission, a conditioner for the internal seals and gaskets, and it cleans the internal parts of the transmission. It also allows the internal clutches and bands in the transmission to slip when needed and grip when needed without breaking down from the heat.
Just like the engine oil, automatic transmission fluid wears out and becomes contaminated and has to be replaced. The equipment we use circulates a cleaning chemical that dissolves varnish and clumps of foulness. Then it flushes four gallons of clean fluid through every nook and cranny of the transmission to ensure a thorough job.
There is a big difference between a true transmission service and what’s called a “pan drop.” With a pan drop, just the fluid in the transmission’s oil pan is drained. That leaves at least 2/3 of the fluid dirty to contaminate the small amount of new fluid. We use only top-quality full synthetic transmission fluid. We feel that the additional cost is well worth it to ensure the best protection.
Power Steering Fluid
Power steering fluid is similar to automatic transmission fluid in the roles that it must fill. One difference is that power steering systems do not have filters. The only way to get the gritty abrasive particles that inevitably accumulate over time out is to flush the system. In an automatic transmission the filter usually catches most of that. Of course, this is also the only way to restore the anti-corrosion, anti-wear, and cleaning additives that are built into the fluid and are used up over time. The gross stuff that the cleaning additives remove from the internal parts also has to be removed.
Transfer Case, Differential, and Manual Transmission Oil
I’m lumping these together because they’re similar in that they have two primary responsibilities – lubricating gears running against other gears, and lubricating roller bearings. The most common problem we see in these components is particulate contamination. This is where tiny metal filings from normal wear have no place to go and act as abrasives on the gears and bearings. We follow the different manufacturers’ guidelines when advising our clients on when to do this type of maintenance unless we see an abnormal build-up during our inspections.