Our recent article on Chrysler's quiet introduction of oil change warning indicators brought reactions from readers. One reader pointed out that in model-year 2011, Chrysler switched from a severe-service oil change recommendation of six months or 3,000 miles to six months or 8,000 miles (in all cases, whichever comes first), while extending the normal interval from 6,000 to 8,500 miles (except SRT).

For 2013, according to this generally-trustworthy source, Chrysler will join General Motors in requiring annual, rather than semi-annual, oil changes, except for SRT and diesel engines, at intervals of no more than 10,000 miles, according to our sources. The automatic oil change indicator will now work for the life of the oil change; the old one "did not adjust the oil drain interval beyond 3,500 miles." It will also add convenience by providing a "percent oil life remaining" display (as General Motors' system has for years), and provide "Change Oil Soon" and "Change Oil Now" displays on the dashboard.

The system works by starting with an ideal oil life (in the number of engine turns), and applies "penalty factors" using oil temperature, engine speed and load, and ethanol content (presumably along with the previously reported items) to come up with a safe estimate of oil life. There will likely be the usual disclaimers regarding people driving in predominantly dusty conditions.

The system can, again, demand oil changes as soon as 3,000 miles from the prior reset, or as long as 1 year and 10,000 miles -- numbers familiar to those who read General Motors press releases. These policies are still unusual for cars sold in North America.

Chrysler warns that the oil changes should be accompanied by tire rotation, battery inspection with terminal cleaning, automatic transmission fluid inspection (where possible), full brake, exhaust, and cooling system inspection, and a review of the air filter.

The longer intervals, for customers that pay attention to them, have the potential to save customers (in the aggregate) huge sums of money while relieving stress on the environment and cutting American oil imports -- albeit not by a large percentage, but certainly by a large number of gallons. Chrysler sold 1.4 million vehicles in the U.S. alone in 2011; if the number of oil changes was cut from two to one per year, it would cut fresh oil usage by 1.4 million gallons per year (most used oil is recycled or burned for fuel). Customers, as a whole, will save around $4.2 million per year on oil changes by going from two to one per year.