I just read in my Standard service contract that the air filter is not replaced until 30,000 miles. Sounds odd to me.

 

That is correct for Schedule 1 and Schedule 2 maintenance cycles. The Premium Maintenance schedule has it replaced at 15,000 miles. I like to change mine every 15,000 miles and check it every oil change. If I feel it is too dirty before 15,000 miles it gets changed. Just remember the dirtier the filter the less air to the engine and decreased performance.

 

I guess when the service is free certain things are no longer seen as necessary.

 

You only need to replace an air filter when it is dirty. Depending on where and when you drive, that could be 5000 or 40000 miles.

 

Spot on. Dirt roads can dirty the filter in 5,000 miles (or less, if the car is driven fast and the road is dry and a continual cloud of dust is raised). But a car that is driven carefully and stays on clean pavement may show little dirt on the filter at 40,000 miles. Best route is to check the filter at every oil change. Replace if dirty.

 

Of course the government has spent an incredible amount of money to determine how much a dirty filter affects fuel economy:

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

From the article: "However, it is very common for over-servicing to occur in these applications due to a lack of understanding of how optimum air filter efficiency is achieved. The standard recommended service life for an air filter in light- and medium-duty applications, during normal driving conditions, is about 30,000 miles. It is common, however, for servicing to occur when the filter appears dirty. Engine air filters are designed to actually increase their efficiency by using this initial layer of dust as an added filter layer. Initial filter efficiency is usually approximately 98% but increases to more than 99% by the end of the service life of the filter. Therefore, changing an air filter before the useful service life is achieved can result in premature engine wear."

Given this knowledge, many users are now employing "Filter Minders" as illustrated in the article. Many of those users are finding out that the gauge doesn't even start to move until 40-50,000 miles. So, many/most of us are actually causing premature wear by changing our filters just at the point that they are reaching their most efficient use.