The company announced the offer at its annual stockholders meeting in Detroit on Thursday.
The offer is good for two years or 24,000 miles, whichever comes first. Oil changes will be done when the vehicle's oil monitoring system says they are needed.
Previously, oil changes were only covered for Cadillacs sold since the 2011 model year.
GM also announced in a regulatory filing Thursday that the government's stake in the company will drop to 189.2 million shares, or just under 14 percent, when it sells 30 million shares of stock after the market closes Thursday.