Originally Posted By: Donald
Or maybe they do it at a loss trying to get you to buy extra services.
That's hitting the nail on the head. I got one of those el-cheapo oil changes back when I got my Buick and needed to get 3 year old short-trip only motor oil out of the engine during a 10*F day. They attempted to upsell me on any/every fluid change imaginable. Granted the car did actually need all those fluids changed, but not to the tune of $500 for everything. $150 coolant flush, $99 brake flush, $150 ATF flush, and a $99 PS flush. I did all that myself later for far less.
It's a good deal for sprucing up an older neglected car. And the techs going over it with a fine-tooth comb will usually alert you to what it needs.