Thursday, Dec 05, 2002 at 01:00
Sorry OziExplorer.. Wrong again!
I've got a ZD-30 based Patrol (rocket ship in third, anything lower is pathetic!) and the manual specifies (page 8-6 and 8-7) that the oil must be changed every 5000K's, with the oil filter every 7500K's unless vehicle is used in hot and dusty environments. The adverse conditions statement says that "If the vehicle is operating in hot or dusty conditions, the vehicle should have the engine oils and filters changed every 55 hours or 2500Kms" (page 8-7)
Additionally, we have a Mitsubishi Triton diesel and guess what? The book disagrees with your statements!
What it comes down to is an application of "first principles" of what the oil actually does. The oil is designed to do two things.
1. It is supposed to COOL the engine components. (Yes I know that it's a water cooled engine, but without the oil performing this function too, you would need components to withstand very high tempuratures!)
2. It is supposed to lubricate the metal to metal friction surfaces, such as bearings, pistons, cam lobes and bushes. It does this by either "splashing" the components, or "immersion" of the component. The oil is either surrounding immersed components, or the oil is pushed into it, as like in a turbo-charger.
In the oil there are detergents, that help
breakdown the blow-back from the combustion cycle, (called soot), heat
breakdown and the dirt and crap that gets into the oil from your breathers and such.
Now, if you use the oil past say 5000K's, or about 90 hours old, the detergent (scrubbing) capabilities of the oil become less effective. What you now have is a very good abrasive compound being pumped around your engine, through your oil-cooled turbo bushes (*NOT* good) and around components such as bearings, cams and cylinder head linings.
Now, in the ZD-30, I have done a few things to make the oil protect a little better. I've added an oil-cooler, (a jumped-up radiator for oil) and a remote oil filter, capable of cleaning down to around 5 micron. (the standard filter goes to about 12 microns and 20 grams of dirt)
What these two devices do is allow the oil to be cleaned MUCH more effectively, by removing carbon deposits from unburnt fuel blowing-by the piston rings, heat damage to the oil and such. Additionally, I have cooler oil as I remove the heat to the oil by using an oil thermostat and oil cooler. This keeps the oil down below the break-up tempurature and prolongs the engine components life. They only cost $145 from Supercheap! The spin-on filter replacements cost about $200 from
Cooma Diesel.
It's entirely up to you as to how you look after your vehicle, but as for me, I stick religously to the book!
Also, it is not possible to
test the oil's performance by "just looking at it". You will need to send a sample to a laboratory! If you have access to a microscope with 400x mag, have a look of dirty oil as compared to the same batch of oil as when it was clean.... It will scare you....
By the way, I haven't found any fully-synthetic diesel oil yet.. I've found a few of the fortified oils though.. Personally, I stick to a Penrite oil, called HPR Diesel Light, as it offers a good spread of tempurature performance, coupled with a semi-synthetic base. It's not cheap, but it's good!!
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