What is the deference between regular oil and Energy Conserving? My Lexus RX300 (2001) says "5-30 ENERGY CONSERVING ONLY" ... But the place I took it to, put in Chevron 5-30... Is that good oil, is it energy conserving?? Also since I got it back from the repair shop, the car drives rather sluggishly... The take off isn't as responsive and before I could spin the front tires from a stop, now I cant.. The car just takes off slowly...