Monday, May 18, 2009 at 01:50
Glenn,
I was at my next oil change Km's about a week ago (I don't do a lot of KM's at the moment per year), and was planning to try a synthetic blend (havent decided which one yet).
Anyway number 1 son decided he needed to "borrow my F truck" while he left me his 80 series cruiser to work on the alternator / PCV bypass proceedures described in earlier posts!
In that week he managed to run up 1000kms (yeah about 3 months worth of my running in a week - he has a G friend in Collie go figure, hence the large additional KM's!
So now I'm 1000 km's overdue for my 5000km change and about to dump the last lot of Delvac 1, when I do the change.
I'm leaning towards Rotella at this point in time because so many of the US F 250 7.3 liter intercooled engined operators report good results with it and good used oil analysis results, some with extended oil change intervals.
I don't like "reporting" bad results with oil unless I have the number of changes & used oil analyses to back up the claims.
I bought the truck at Xmas 2006, with 104,600km's on the clock and since then in 2.5 years, have only just done 126,000 km's or a total of about 21,400 KM's or 4 oil changes @ 5000km intervals if that makes sense.
All of those have been the
Mobil Delvac 1, which I've Used Oil Analysed at a couple different labs (Cat Australia at the local westrac place & Oilguard labs in the USA).
Both
places show high nitrate sulphate and excessive oxidation results, although all the wear metal rates etc were fine - its just that the damn add pack doesn't seem to last.
I'm about to change and to be honest, I'm still researching what to.
It'll likely take me another 2 years to get any meaning full data on the next oil I select purely becaise I do so few Km's per year now.
The reason I say that others mileage may vary (why they may have different opinions), is this.
My diesel 7.3 liter V 8 intercooled turbo diesel engine isn't stock standard.
I have added "Diesel Gas Australia" LPG injection to
mine and it IS possible that the early oil degradation (principally oxidation, but also nitration and sulphation) is due to the higher cylinder operating temps because of the LPG injection.
It wouldn't be fair to compare my used oil analysis results with a standard Diesel turbo engine from another vehicle that isn;t gas injected.
It seems that while these Gas conversions are very popular for the extra HP and MPG's as
well as extended range, the oil companys have been caught "on the hop" by the sudden increase in the number of engines so modified - due to the Govt rebates incentive.
As yet they are not blending and selling oils specifically for the diesel gas conversion engines yet - which generally run at slightly elevated temps.
They MAY eventually do this, it depends upon demand which at this point in time is small and localised to
places like Australia which are only relatively small markets.
The engine gas conversion co's like Diesel Gas Australia - do mention on their websites that, it is possible for the first two oil changes after conversion to get elevated carbon levels in your oil as the gas injection cleans out built up carbon deposits within the engine.
I've done 4 changes now, since conversion - without any improvement in the condition of the oil judging by the tests results.
The oil testing is not a definitive science either, I actualy sent duplicate identical samples to the two different testing labs, and got results back from the two labs that don't agree with each other. (minor differences in measurements) and was advised when I queried them - that each company uses it's own testing methods, which return differen results depending on the method and equipment used.
Oils in engnes is NOT a very exact science...has been my experience after delving deeply into it and after discussions with oil industry experts at forums like BITOG (Bob IS The Oil Guy).
It's a fascinating intricate topic, but ends up the more you get to know, the less definitve your answers will tend to be and bye the time you've workled it all out - you've worn out your engine or traded that vehicle on another and need to start the whole process over again.
I learned that in response to new Govt clean air regs like those introduced in California and Europe - oil co's "re-formulate" existing oils from one batch to another in order to comply with the requirements ofr emissions and catalytic converters and so on and so
forth.
Just coz you always bye the same jugs of oil brand at auto pro - doesnt mean your puting the same oil into your engine from oil change to oil change.
Most of the companys have been reducing or eliminating Calcium levels from above 3500 ppm down to zero and replacing it with low levels of Molybedum as a neutralising agent. Thats fine in some slow revving diesels, but a LOT of the high revving Japanese engines run at average temps
well above the
breakdown temp of Moly!
Oil is a big topic - as you can tell from the fact there are oil discussion forums around the world on just that one topic.
While most users pick a brand favourite in much the same way as they pick a footy team and stick to it for life, and it works
well for them - others chop and change to every new fad, with little idea in basis of facts as to why.
Few people do regular used oil analysis testing - even fewer
test their virgin oil before they add it to the engine to see if it is the same blend as the last lot they bought!
Unless you KNOW what the levels of certain thing are in the oil when it was NEW - how meaningfull are levels repioorted in the used oil analysis?
You might have high zinc levels in your UOA result - BUT does that mean some zinc component within the engine is wearing abnormally - or was the high zinc level part ofthe brew of add packs the oil blender added for old engines with flat tappets to slow cam lobe and lifter face wear?
Its a big subject and I prefer not to be too dogmatic about any issue without facts to back it up.
I don't reckon it adds a lot to the discussion unless you have the facts to back up your opinions, one mans trash might be another mans treasure, and so it is with oils.
Cheers
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