I'm using 10w40 liquimoly in my union star since 2016 and it's been good.. My change interval Alway have been 2-2200... And it never burns... All other cheap oil start burning at 1000 mark.
And best way of engine flushing is adding liquimoly engine flush to ur old oil and start it and let it on slow running. And other alternative is add 50-60pkr diesel to oil and let it start on slow running...
And repeat it by adding one khula oil 0.7L and let it run 10mins on slow running and then u will see clear oil coming out.