Try some Schaeffers Moly 132 additive with your current oil to slow consumption and add other benefits. This has helped consumption in several customers' engines that were otherwise perfect. Or just get some Schaeffers series 9000, either 5W-40 or 5W-50 for year-round use. All 3 products are excellent. Contact bitog Schaeffer rep for info. Here's some reading.
http://www.schaefferoil.com/datapdf/132.pdf
http://www.schaefferoil.com/datapdf/9000.pdf
http://www.schaefferoil.com/datapdf/9001.pdf
http://www.schaefferoil.com/datapdf/132.pdf
http://www.schaefferoil.com/datapdf/9000.pdf
http://www.schaefferoil.com/datapdf/9001.pdf