Replaced Water Pump,
Join Date: Aug 2009
Location: New Zealand
Yes 10W40, stick with name brands, change regularly with a fresh oil filter everytime.
Synthetic oils are more stable and generally last longer as far as viscosity range doesn't deterioate as quickly (oil not thinning out as much when hot and/or thickening when cold), than semi-synthetics (good) and dino oil (not as good). So as a rule can be run longer between changes (Caveat: the manufacturer's change intervals should be seen as the maximum time/milage between changes).
Be aware that all motor oils contain an 'addtives package' of things like detergents, friction modifiers, dispersants, anti-foaming agents, etc, which improve the oils performace in stopping wear. These additives are used up during normal operation. The tiny particles created by combustion and normal wear and tear are suspended in the oil by these additves (oil turns black), with the larger bits trapped in the filter. With modern motoroils, especially the sythetics and semi-synthetics, the depletion of the addtives is the primary reason for oil changing, as these get used before any really detrimental degredation of the base oil occurs. Which is why it can be recycled.
New modern cars factory filled with synthetics can make use of the oils longevity -new MBs are oils changes every 20,000 mi (afer an initial one at 10K) from memory. Older, more worn engines will use the additves quicker and the longer life of synthetic base oils aren't too much of an advantage (unless you are red-lining your car regularly on daily basis, or placing it under some other unsual stress).
Personally I use a name brand (who makes the stuff MB USA has in their white bottles) semi-synthetic and change no later than 7,000 mi.
Darryl in New Zealand