Whats the best engine oil for my zd30 with 170000 kms and how many litres

[4bye4]

Ok stupid question but there seems to be a fair difference between 5w 40 - 15w 40. What advantages do each of them have over disadvantages? Or is it just preference? I have 170k kms on clock & last service was 166k so im thinking do/ should it be serviced every 5k kms or 10k kms? I have heard mixed opinions so far! Ps Just bought it 2006 GU IV ST!

Ok, to answer this question properly needs a degree in science and about three days but;
As oils heat up, they generally get thinner. Single grade oils get too thin when hot for most modern engines which is where multigrade oil comes in. The idea is simple - use science and physics to prevent the base oil from getting too thin when it gets hot. The number before the 'W' is the 'cold' viscosity rating of the oil,often called the Winter rating, and the number after the 'W' is the 'hot' viscosity rating. So a 5W40 oil is one that behaves like a 5-rated single grade oil when cold, but doesn't thin any more than a 40-rated single grade oil when hot. The lower the 'winter' number (hence the 'W'), the easier the engine will turn over when starting in cold climates.

oils.jpg

Given our climate, there is pretty much no diference between a 10W or 15W lower oil, and as both 40 and 50 oils perform to 50*, It doesn't make much difference in WA. Get the best priced quality oil either 10W40 or 15W50 you can afford. If you are going on a desert run or in snow country or very long hot or cold runs you may want to use a more specific rated oil for the duration.
Don't mix synthetic and mineral oils. I don't mix brands unless I have to.