Your mechanic may be smiling because he's charging more after a six-year decline in maintenance and repair costs.

If your calendar app hasn’t reminded you, it’s National Car Care Month. Now, Americans have a day, week or month to celebrate just about everything from artichokes to kazoos, but after a long winter’s abuse, this is probably something most motorists should take seriously.

A bit of preventative care can head off some much more serious repair bills later on. And the bad news is that after benefiting from an unusual, six-year reduction in automotive parts and labor costs, a new study suggests that your service and repair bills are fast on the rise again.

They rose an average of about 10% last year, reports auto service website CarMD.com. But the study does have a bright side – at least for the small cadre of hybrid vehicle owners. It found that the cost for fixing those vehicles actually dipped a bit as they became more commonplace.

The increase “can be attributed to factors such as a market correction and a higher percentage of more expensive repairs related to the aging vehicle population,” explains Ieon Chen, the CEO of CarMD.

According to data compiled by the used vehicle tracking service The Black Book, the typical vehicle running down U.S. roads today is about 11 years old, making it the most aged fleet ever. And even though most studies show that today’s vehicle are more reliable than ever the simple fact is there comes a time in every car’s life when those repair bills start to escalate.

CarMD’s survey of owners and service facilities found a 24% increase in the frequency of “catastrophic repairs” last year, perhaps revealing that many owners had tried to save cash by putting off both routine maintenance and even more serious repairs during the depths of the recession.

When it comes to basic spring maintenance, there are a number of key steps to take. Some are basic, like washing off winter grime and salt to reduce the risk of corrosion.  It’s often a good time to change your oil, check tires for proper inflation, ensure that fanbelts aren’t showing excessive wear, and check spark plugs cables and other wiring, especially around easily corroded battery terminals, to make sure they’re solid.

A more extensive check-up will likely handle wheel alignment and look for possible damage to suspension parts due to jarring the car across ruts and potholes. And your owner’s manual might call for a tune-up, though intervals have been stretching out on newer models.

The CarMD study tallied up the results of 161,000 separate repairs handled by ASE-certified technicians, though it also asked shade tree mechanics about the work they did themselves.  And one finding was that owners appear to be getting more savvy about making minor repairs that can save them a trip to the shop – even though fewer motorists appear to be handling such traditional maintenance duties as oil changes.

The study reveals that the cost of repairs can vary widely depending upon where you live, and it found that the increase in costs from 2011 to 2012 was steepest in the Northeast, at an average 11.56%. At the other extreme, repair costs rose a more modest 6.53% out West. The average was 11.02% in the South and 8.98% in the Midwest and Northern Plains.

As to what were the most common repairs? The survey found the number one problem to be the need to replace a faulty oxygen sensor, a job that averaged under $300 and accounted for 8.3% of those 161,000 repairs. Oh, and if you plan to ignore the warning light on your instrument panel keep in mind that this can be a costly mistake, potentially increasing your fuel bill by as much as 40%.

Second on the list? “Tighten or Replace Fuel Cap.” That, it turns out, can be an easy and inexpensive fix but, again, ignoring the warning can decrease fuel economy by 0.5% — and dump harmful emissions into the atmosphere.

Third on the list, replacing a faulty catalytic converter is likely to be an expensive job, averaging $1,101.44, an increase of 7%, found CarMD.

Other common problems included replacing ignition coils and spark plugs, and various fixes to vehicle emissions systems. But number seven on the Top 10 list was “Remove Aftermarket Alarm.”

We’re not sure that this problem is triggered by a warning light on the instrument panel as much as complaints from family and neighbors. Whatever the reason, the study found it cost an average $98 in labor, a 20% increase for 2012.