Entering the second quarter of 2009, we’ve made three changes to the Car Reliability Survey.

First, major preventative maintenance, most notably timing belts and water pumps, now should be reported on the repair survey. This change has been made to equalize results between engines with timing belts and those with timing chains. Those with timing chains generally cost less to maintain, because there’s no set mileage at which timing chains must be changed. With timing belts, there is a set mileage at which they must be changed. This involves hundreds of dollars in labor, so water pumps and other relatively inexpensive items in the same area are changed at the same time. Because of such preventative maintenance, a survey that asks only about repairs would make engines with timing chains appear less reliable.

What we’ve done to equalize results up until now: water pump failures have only been included in the analysis if they occur before 70,000 miles.

Second, we’ll now ask about mods on the “no repair” survey only when a member first responds and then each January after that. Very few members have mods, and this will reduce the time and effort involved for the 95+ percent that don’t have them.

Finally, when we first created the survey we thought it would be easiest to have people round their odometer readings downward, since they’d simply have to read the numbers off their odometer–and simply drop the final three digits. But this isn’t how people are used to rounding, and quite a few probably rounded up when the last three digits were 500+. In general, it’s not a good idea to deviate from common conventions unless there a very good reason for doing so.

There isn’t a very good reason in this case. Only an attempt to simplify the survey, which didn’t actually simplify it. So the survey now simply asks that the reading be rounded to the nearest 1,000. The average readings should increase by about 500 miles as a result–not a significant change.