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Those Shop 'Add Ons' That Aren't Really All That

Mechanic Under Car

We've all heard the stories about the person who took their car in for a tire rotation or some other free (or nearly free) service and ended up paying thousands for repairs and maintenance that was "missed." There are a lot of ways for a shop to take advantage of a person's lack of knowledge.

Not every repair shop is out to scam you, of course. Most are honest businesses and a good mechanic who's honest is far more likely to be too busy with legitimate work to be running scams to make extra boat payments. Still, there are some things that are common "add-ons" to up the service price at some shops and there are some phrases or terms that may mean one thing to you and another to the service manager.

Intake Cleaning, Filter Replacement

The "lube shops" that specialize in fast oil changes specialize in fast fluid exchanges and filter swaps. They also like to throw on "extras" to boost their profits. Air filters often do need replacement when the lube shop recommends it, but check their price before you give the OK. Quite often, they inflate the cost of the filter by 50 percent or more. Also beware of "intake cleaning" as it's not often recommended by manufacturers and is likely just a waste of money on your part.

Even better, both of these are things you can easily do yourself in your driveway or at the parking lot of the parts store for far less than the lube shop will charge.

Radiator Flush

If the interval for an engine coolant replacement is up, make sure that the "flush" the shop will do is a simple fluid exchange and nothing more. Some shops use the term "flush" to mean adding solvents or chemicals to the engine coolant in order to "clean" the old fluid out.

The trouble is, those chemicals and solvents don't always get pushed all the way out once the flush is over and they can break down under the pressure and heat of an engine operating, causing problems later.

Nearly all reputable mechanics and manufacturers recommend that you merely drain the old engine coolant out and replace it with new fluid. At most, circulate clean water through the system after draining the old fluid. Use only the recommended anti-freeze mixture (usually 50:50 anti-freeze to water). Many recommend using distilled water to reduce problems that can be caused by hard water in the radiator.

Transmission Flush

As above, a "flush" may not be a simple drain and refill. Further, some transmissions have filter replacements to go with the fluid exchange, so be sure that's included in the deal.

Nitrogen-filled Tires

This is a fun one and can be the subject of much debate. There are some who claim that nitrogen-filled tires provide better fuel economy. This comes from the fact that it's used in aviation and by many racing teams. The reality is that the claims are a bit dubious and often don't include certain caveats.

The greatest advantage of nitrogen is that it's more inherently stable than air. Air is mostly nitrogen, yes, but it's the 20-odd percent of air that isn't nitrogen that can become "flexible" in some situations, making it less stable.

Nitrogen-filled tires have a slight advantage during the winter months, when temperatures swing tens of degrees every day, often dipping below freezing overnight. This can cause air-filled tires to lose some pressure, lowering their fuel economy rating. The change, however, takes time, and those who regularly check their tire pressures (recommended monthly) and keep them full will not see those ill-effects. Given the cost of nitrogen versus an (often free) air fill, the savings can be a bit questionable.

Fuel System Cleaners

There is a lot of debate about whether or not these are necessary. Most mechanics agree that cleaning out the carbon deposits through the fuel system is a good thing and many recommend specific products for doing so. The question is not so much whether or not you should do it as it is what you should use. The short answer is simple: use whatever you feel comfortable using if it gets the job done. Some options might be cheaper than others, but what matters most is that whatever you're using actually works (most of the solvents sold for this purpose work on some level) and that you use it consistently.

Some manufacturers have chimed in on the use of fuel additives for system cleaning. Some recommend specific brands or formulas, but most merely recommend an interval (usually every other oil change or every six months). Check your owner's manual.