Wednesday, Apr 22, 2009 at 17:35
25,000 km extended oil change intervals are possible, BUT (n.b. its a big but), NOT without several modifications to oil filtration AND having regular used oil analysis performed on the oil during it's lifespan to protect against excessive wear.
1. Youd need to add a sub micron bypass filter to remove a lot of the carbon (soot of combustion) from the oil - otherwise it becomes like a grinding paste and wears your cylinders and rings and bearinsgs etc.
Sub Micron means less than ONE micron in size. you standard filter allows particles about 25 microns or less in size to pass - and this onclused all the soot of conbustion (carbon particles).
2. Another way to remove this soot of combustion is with a centrifuge oil filter, like the Land Rover Doscovery T diesels run standard.
3. You COULD run both sub micron bypass AND centrifuge filters in addition to your stadard oil filter/
4. You still need to take samples of the oil and post them off to the lab (CATERPILLAR HAVE SUCH A LAB HERE IN WA) at westrac equipment - for used oil analysis to see if the oils lubricity and viscocity remain within specification for youre engine and to
check for excessive wear metals presence as
well as soot buildup levels.
5. Another reasn to run the Used Oil Analysis - is to
check the condition of the oil "add pack", chemicals added by the manufacturer - to neutralise acids formed by combustion and blow by of combustion gasses past the rings and into the sump and it's oil.
These USED to be calcium in large mounts >3500ppm in some cases, but now with more modern diesels, and the advent of catalytic converters in the exhaust systems - companys are re-formulating their oil toi use much lower amounts of molybednum as a neutralising agent in their diesel oil.
One problem with that - is that the moly has a break down temperature a LOT below what some of the older Japanese turbo diesels normal operating temperature runs at and as a result these new fangled synthetics don't last the distance in some of the older Jap T diesels (Like my old 4.2liter 1HD-T Cruiser) and at standard 5000 km change intervals - i get used oil analysis saying that high oxidation levels are detected (burnt oil from excessive heat).
Personally I've given up trying to get extended oil change intervals - and I have sub micron bypass filtering fitted - and use expesive Mobil Delvac 1 fully synthetic oil, as
well.
The used oil analysis results consistently come back telling me that the add packs used up within 5000 km's and to change oil.
What cost a new diesel engine - versus what cost regulat 5000 km's oil changes?.
You can read a LOT (and ask questions) about extended oil change intervals & Redline oil etc at BITOG forums (Bob Is The Oil Guy) if you google search for it.
Some people do get 25,000km intervals on their oil, BUT they also do the relevent testing to make sure they aren't causing damage to their engines - and it seems aLOT of the new oils are better suited to the NEW US manaufactured diesels than they are to the older Japanese diesels.
There are findamental differences in design between thesetwo types of T diesel engine in the distance down from the corwn on the piston to the first compression ring - with the USA engines having the top ring much closer to the top of the piston and the Japanese design having them much lower down.
Usual operating temps are a lot different too.
Some of the best oils out of the USA do
well in USA designed T diesels, and sometimes not so
well in Japanese designed ones.
Principally it is due to the difference in ambient operating temps and the type of add pack added to the oil.
Extended oil change intervals isn't smething to get involved in unless you know EXACTLY what your doing in my humble opinion - speaking as someone who has dabbled a bit in this area!
Cheers
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