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Maintenance & Repair Engine Oil - A slippery subject Part 2
3505 messages, Last post on Mar 18, 2009 at 6:13 PM
You are in the Maintenance & Repair Forum. Your Host is mr_shiftright
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On another forum here someone posted: Around 2000, Ford (and perhaps, Honda) changed the engine oil specification from 5W-30 to 5W-20 for many vehicles. This was done without any actual engine mechanical changes. The reason was to improve fuel economy... Is this correct and if so does it mean that you would improve your engine's longevity by using 5W-30 even though the manufacturer specifies 5W-20?
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Replying to: jeffyscott (Mar 24, 2008 10:50 am) |
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Replying to: shipo (Mar 22, 2008 6:44 pm) Thanks for the trip down memory lane regarding http://www.plastigaugeusa.com/. The last time I used that product was when I replaced the rod bearings on my 51 Plymouth just before graduating from HS in 62.
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Replying to: richardson (Mar 24, 2008 6:47 pm)  The good news was that the car was still running some 40,000 miles later when I moved away from San Diego and changed my career from turning wrenches on cars to tickling keys on computers. 
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I was chatting with a friend who, among other things, is an expert Porsche engine rebuilder and Porsche/Audi technician. He was of the opinion that extended oil changes get rather risky over time, because as the oil nears the end of its supposed extended oil change cycle (let's say 10,000 miles), it returns to its "base stock"; so in effect if you are running 5W-30, at the end of your cycle you are really running 5W oil on cold starts. Not so good. Any opinions about this? |
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Replying to: Mr_Shiftright (Mar 25, 2008 6:25 am)
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Replying to: wtd44 (Mar 25, 2008 6:48 am) Also he's used to dry sump engines with huge oil capacities, so maybe that has something to do with his concerns.
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Replying to: Mr_Shiftright (Mar 25, 2008 6:57 am) |
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Replying to: Mr_Shiftright (Mar 25, 2008 6:25 am) A few points: 1) I use Mobil 1 0W-40, and if your friend was to be believed, my oil would effectively be a 0W after my normal ~11,000 mile OCI. 2) Per my most recent 11,500 mile UOA result, the Mobil 1 0W-40 sample that I sent in came back with a comment saying "The viscosity measured in the correct range for a 0W-40..." 3) Unlike conventional oil, the full synthetic oil that is approved for use in Porsches (Mobil 1 0W-40 being one of the approved oils) doesn't use any viscosity improvers to enable the multi-grade rating. How can that be? Simple, the PAO base is so stable that it naturally exhibits multi-grade tendencies in that it doesn't thicken as much when extremely cold, nor does it thin as much when at operating temperature. 4) My bet is that your friend is telling you what he believes to be true, however, he has zero science to back up his beliefs. Best Regards, Shipo
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Replying to: shipo (Mar 22, 2008 6:44 pm) My kid did some testing with the temporary oil pressure guage on and he found pressure was okay until the water temp got to within about 10-15 degrees of the normal fully warmed up temp. Based on this and some straight-line interpolation of viscosity numbers, it may be that a _W-50 (or _W-60) will be enough to keep the light off...or at least it will come on less often. Also my thinking is if the pressure loss is that intermittent and infrequent (only at idle and only when engine is hot), it's likely the parts are still remaining pretty well lubricated, since the oil that is on the parts would not disappear the instant that pressure is lost. |
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