Driving approximately 70-75mph on highway with cruise control set. Car starts to make rattling sound & engine warning light goes on, car struggles to accelerate and hovers around 60mph. Upon inspection of engine oil in car, fresh oil has been burned up quickly! Added 1 quart. Drove 45mins at 70-75mph. Notice Engine light on again. Check engine oil. Had quickly burned through 1qt! Add new quart of oil. Let car rest overnight. Driving 70mph without use of cruise control. Then use cruise control. After a bit car engine sounds of rattling & struggling to accelerate. RPM gauge seen going up & down. Through rear view mirror I see lots of bluish smoke. Pull over to let engine rest. Check oil = still 3/4. Use engine dectection device. Indicates that cylinders 3 &4 misfiring. Reset car warning indicator with my detection device. Finish drive going 60mph to arrive at destination without car engine warning going back on.