Instead of arbitrarily changing the oil, send a sample to Larry, and findout what condition it's in. He'll even report the hot viscosity.
On 6/26/06, LT Don <[EMAIL PROTECTED]> wrote:
You are an engineer, aren't you? I can smell them -- my son is one. On 6/26/06, Peter Frederick <[EMAIL PROTECTED]> wrote: > > Actually, viscosity ratings are more complicated. In the old days, you > have an oil of a particular viscosity (actually flow rate at a certain > temperature). Petroleum based oils have a significant change of > viscosity with change in temperature character -- when hot, they get > VERY thin. When cold, of course, they aquire the flow characteristics > of molassas, what ever the room temperature viscosity. > > The solution was to add materials that didn't change viscosity so much, > so that an oil mixture would have "multi-viscosity" characteristics -- > that is, flow like say a 10 wt oil cold and a 30 wt oil hot. The > rating is cold viscosity rating number first, followed by hot viscosity > rating, so a 10W-40 oil flows like a single rating 10W oil cold and > like a single rating 40W hot. > > The base fluid used in synthetic oils doesn't change viscosity with > temperature nearly as much as petroleum base oils, and in fact is > fairly hard to rate using methods for petroleum base oils. 0W-30 > synthetic oil pours like cold diesel fuel, but I'd not want to use > diesel fuel as an engine oil -- wouldn't stay in the engine! > > The smaller molecules will likely burn off first, since they are more > volatile, but I suspect there really aren't that many in synthetic oil. > The majority of oil consumption in a good condition engine is burnoff > from the cylinder walls as they are exposed during combustion, along > with whatever amount burns off the valves from clearance on the stems. > Synthetics are very resistant to oxidation (remember the frying pan on > the grill ads?) so they don't burn off the cylinder walls, and the > molecules are fairly large so they won't evaporate. No modern oil has > components light enough to actually vaporize, I would venture -- they > would also carbonize too easily, leading to excessive sludge. > > What the viscosity of a mixture is would be hard to determine without > actually testing it, and I suspect what you would have would be xxW-50 > -- the viscosity "extenders" would work their magic more at the hot end > than the cold end. > > Fun stuff, eh? No wonder oil threads go on forever! > > Peter > > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > -- "There're always enemies, George. Jesus had enemies." -- Tom Clancy, _Executive Orders_ 1977 240D 1983 VW Quantum turbo diesel 5-speed 1972 Honda CB-500K motorcycle http://www.airamericaradio.com/listen _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
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