Chevrolet TrailBlazer, Service Manual, Page: 24 / 677

atmosphere. Over time moisture in the brake system will lead to corrosion and damage to
internal parts. Also, a sufficient level of moisture in the fluid can dramatically lower its
boiling point. Should temperatures during hard braking (mountain driving, trailer towing,
racing, etc) allow the brake fluid to boil, you could experience and sudden and complete
loss of braking ability. So if you plan on keeping a vehicle for any length of time, and/or
you use it under harsh conditions (such as towing or racing), you would be wise to follow
our fluid replacement guidelines.
But the Replacement Part is different?
Another thing to remember is that maintenance intervals may vary with the type of
replacement parts which are used. Spark plugs and synthetic oils are two good examples
of this. Although we have suggested changing your oil and filter every 3,000 miles, use of
a synthetic oil may allow you to lengthen or even double this mileage, IF your usage fits
the proper patterns (highway miles, above freezing, with little stop-and-go and no
excessive speeds . . . ). The recommendation we give for spark plugs is based on
conventional plugs with an electronic ignition system, which probably covers most vehicles
on the road. If you have an antique that uses a points ignition, well then you will probably
have to replace the plugs more often. But, if you use special plugs, like the increasingly
popular long-life Platinum plugs, you may easily be able to double the recommended
replacement interval. The key here is to pay attention to the directions supplied with your
replacement parts (and if you have never replaced an item before, check with the
manufacturer for suggestions about original equipment).
Is My Driving 'Normal' or 'Severe'?
Sometimes we are puzzled at how manufacturer's chose the term "Normal" for the style of
driving which most refer to in their maintenance charts as the opposite of "Severe." Check
your owner's manual and you will likely see that you are NOT normal. Sorry to be the one
to tell you, but it's probably true.
You see, to be "Normal" according to most manufacturer's driving and maintenance
recommendations you would have to: Drive the car for more than 10 miles or so (to make
sure it properly warms up) almost every time you start it (never under freezing conditions,
but not in excessive heat, dry or dusty conditions either). Most miles would have to be on
the highway, NOT stop-and-go (few red lights or stop signs), with no excessive idling (in
traffic or curbside), but NOT at excessive speeds. Well, some of you reading this will find
that this applies . . . but most wont.
If ALL of these conditions apply, then most manufacturers call your driving style "Severe"
and lump it in with trailer towing, racing, cab or delivery driving or even police or fire
vehicle usage. The truth is that most usage probably falls somewhere in between. Actual
severe usage, such as those that we have just listed, should require a LOT of attention to
all of the various systems of a car (including early replacement of all fluids). But, the
average person, who does not race or tow, will be fine with the 3,000 mile/3 month engine
oil change and most of the other recommendations we have given. If you compare those