2005 2.4 lite Toyota carry let has 201000 miles and is burning oil castrol syntec 0W-40 about 3/4 quart every 1500 miles. What can I use to free up piston rings & oil rings in oil crankcase? Also getting bad gas mileage been using gum out in gas tank used 4 bottles 16 Oz so far only averaging 25 miles per gallon.

25 is about what those things get. And that small oil useage is normal according to toyota. No cleaner willffix that, but do change the pcv valve and pray it's just that