2002 Lexus RX 300 burning oil

Vehicle is burning oil. add every 500 miles. no apparent oil leaks. Use of oil stablizer has reduced sometime white smoke when starting to virtually none. valves knock sometimes. Oil pressure light comes on, add oil. on recent 400 mile trip both check engine and vsc lights came on. Phone call to dealer said most likely was sensor. kept driving and it has now gone off or burned out. one opinion was new engine needed. only had vehicle less than a yr. any advice? $3,700 for a new engine ouch!