With regards to 5w-40 engine oil: from http://www.penriteoil.com.au/products.php?id_categ=1&id_subcateg=1&id_products=1 http://www.penriteoil.com.au/pis_pdfs/PI_HPR%205.pdf "Greater engine protection at operating temperatures compared to 5W-30 oils due to higher operating viscosity." "Semi-synthetic for the latest generation of high performance engines, particularly those with variable valve timing. Use where SAE 5W-30 or 10W-30 oils and ILSAC GF-3/GF-4 fuel economy oils are called for." (1) I have learnt here that better flow equals better protection, and a lower viscosity oil has better flow. (2) Why recommend a non-ILSAC engine oil for uses where ILSAC engine oils are specified? I would say Penrite Oils subscribe to the thicker is better philosophy?