fesycresy
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| posted on 22/4/08 at 07:54 AM |
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Old Oil - Thick or Thin ?
As engine oil gets old, when it's hot does it become thicker or thinner than new oil ?
Thanks.
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The sooner you fall behind, the more time you'll have to catch up.
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madmandegge
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| posted on 22/4/08 at 07:55 AM |
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From a total novices point of view, do the bits of metal in it play any part in it being thicker? 
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Mr Whippy
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| posted on 22/4/08 at 07:55 AM |
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Thinner, it becomes diluted with petrol, the petrol is getting past the piston rings on the compression stroke.
[Edited on 22/4/08 by Mr Whippy]
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procomp
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| posted on 22/4/08 at 08:10 AM |
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Hi there are some good bit's of info explained regarding oil on the WSCC forum. Here is a direct link to the basic explenation but there is
other more techie part as well. LINK 1 And
LINK 2 To the page with the other info.
Cheers Matt
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02GF74
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| posted on 22/4/08 at 08:13 AM |
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i vote for thinner; from what I recall, the large hydrocarbon molecules get "chopped up mechanically" (oil pump,etc so become smaller.
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rusty nuts
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| posted on 22/4/08 at 06:34 PM |
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Can go either way, have seen oil like treacle but then again I've seen oil like water. May depend on the type of oil , the quality , the type of
use and how old it is.
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MikeRJ
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| posted on 22/4/08 at 11:31 PM |
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The long chain molecules getting chopped will lower it's viscosity.
Heat tends to evaporate the lighter fractions of the oil, making it thicker.
Combustion products entering the oil make it thicker, e.g. sludge formation.
IME the thickening processes tend to win if the engine oil is left long enough.
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Peteff
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| posted on 23/4/08 at 08:53 AM |
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My nephew's Calibra engine was knackered by cheap oil thickening up. It coated the gauze on his pickup pipe and starved the crank. It was like a
layer of tar on everything in there.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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