Good evening. I own a 2003 Land Rover Discovery 2 v8 which I have owned since 2008 and now has 330,000km on it. I have religously changed the oil every 5000km and since 2010 I used Penrite HPR5 and then HPR10 oils.  I changed to HPR10 becuase I often drive in western NSW during summer where he outside temp can get up to 45c.  I recently changed my oil and did an engine flush and after adding new HPR10 10w50 and new filter I started getting a loud tappet tick after startup which went away after complete warm up. Several other discovery v8 owners suggested using your HPR30 20w60 as a solution to ticky tappets after startup which I recently did and this seemed to fix the tick.  My question is in my situtation what would be the best Penrite oil to use in my V8 with 330k km and driving in warm dusty climates? HPR30 or woud you suggest HPR15 15w60? Regards Mark