Gulf 20-50 vs other 20-50 mineral oils

Technical advice Q&A

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pmansson
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Joined: Sun May 16, 2010 8:31 am
Sweden

#1 Gulf 20-50 vs other 20-50 mineral oils

Post by pmansson » Tue Nov 10, 2020 3:56 am

I have used the same oil for 20 yrs and been very pleased (Swedish private brand but made by the same refinery as Esso used for their, more expensive products).
Last year I began using Gulf’s MAX and Classic. Almost identical but the metal can Classic has more zinc. Twice the price to my previous oil.
What I cannot understand is the perceived difference in viscosity. Both are 20-50 mineral but the old oil is like ”molasses” and the Gulf oil is like a synthetic 10-30 oil, i.e. It pours like ”water” in comparison.
This is very evident wheh filling the XK engine, as it takes time for the oil to make its way diwn the engine. The old oil took twice as long to fill compared to the Gulf oils.
Can anybody explain this phenomenon???

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abowie
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#2 Re: Gulf 20-50 vs other 20-50 mineral oils

Post by abowie » Tue Nov 10, 2020 4:46 am

It's not actually what they say it is?
Andrew.
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PeterCrespin
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#3 Re: Gulf 20-50 vs other 20-50 mineral oils

Post by PeterCrespin » Tue Nov 10, 2020 11:16 am

Different container neck ID.
Different funnel?
Different workshop ambient, or oil storage, or engine temps?

I don’t know how to measure an accurate Stokes number but comparing samples would be easy at the same temp and apparatus. Use either a tall bottle or measuring cylinder to time how long a small bearing ball or nut or lead shot takes to fall to the bottom. Easy to compare time for that, or time taken to drain, say, 250 ml through a 5 mm hole. If the Gulf oil is very different from at least two other types (in case Gulf is the correct one) then you know there is a technical comparability issue.

However, what use is such information? The thinner one may be better in winter and vice versa in summer. But the real issue is at running temps and that depends on viscosity improvers and I wouldn’t mess around with hot oil experiments. Even relative oil gauge pressures are not all that useful because high flow cools bearings better and plain bearings operate on oil wedge pressure not pump PSI / kPa.

So other than curiosity value on a quiet day, I wouldn’t bother researching the question as there’s no obvious use for any answer.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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