Gulf Classic 20-50 mineral oil

Technical advice Q&A

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pmansson
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Joined: Sun May 16, 2010 8:31 am
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#1 Gulf Classic 20-50 mineral oil

Post by pmansson » Mon Jul 15, 2019 4:57 pm

I have used several brands of this oil in my Jaguars over the last 35 years.
Recently Iwas convinced that the Gulf oil with extra high level of zinc additive (more in the 5L metal cans than in the 4L plastic cans) is even better for our engines.
I have now used it for the 2 most recent oil changes. What immediately struck me is how fast the oil goes through the cyl head and block. Took about half the normal time.
It flowed like the 5-30 synthetic oil that my wife´ s Audi uses.
How can this be possible

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SESH
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#2 Re: Gulf Classic 20-50 mineral oil

Post by SESH » Mon Jul 15, 2019 6:25 pm

Also worth considering Valvolene VR1 20W50 Racing Oil.
I always use it in my V12.
Seems to tick all the boxes and has also been recommended to me by a number of engine builders.
Mike
1973 Series 3 OTS Signal Red

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lopena
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#3 Re: Gulf Classic 20-50 mineral oil

Post by lopena » Tue Jul 16, 2019 6:42 am

+1 on the Valvoline VR-1 20-W50 racing oil...my engine builder was emphatic about using it.

Alan
N.J.

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Marquis Rex
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#4 Re: Gulf Classic 20-50 mineral oil

Post by Marquis Rex » Fri Jul 19, 2019 4:12 pm

From engine design and test experience, its not only Zinc Level but Phosphorus level you're interested in.

An engine I designed recently (which has a valve train very similar to a modern Jag AJV8 (funny that!) but made in China, had problems- and the cams would wear from excessive idling. Idling is the worst case in terms of Hertzian conact stress due to a lack of oil film build up.

Later digging- we found that it was due to a lack of phosphorus in the bucket tappet/camshaft interface.

Worst case for old engines are 2 valve pushrod-flat tappet. This is because 2 valve engines typically have bigger heavier valves and higher associated spring pressures, push rod architechture makes it worse because you typically have a higher valve system mass and again higher associated spring pressures- therefore Hertzian contact stresses.
Next is a two valve direct flat tappet- 2 valve- like our XK engines. Again due to the higher spring pressures

Ive never heard of issues with 4 valve Direct acting like modern Jags, the AJ27 has a very light valve system mass of only 100 grams.

For pushrod or old school two valve flat tappets I would aim for Nominal phosphorus level of 1100plus.

1600-1750 is Better. Im quoting Nominal Phosphorus Level PPM and Nominal Zinc Level PPM.

Most modern oils for production engines are down at 650-800 now- this is to do with the emissions system.

Mobil publishes their phosphous and Zinc Levels, I cant find anything for Castrol or anyone else.

I'm a firm believer in synthetic oils. Yes, even for older cars. The old wives tales about synthetics leaking is just that. (it came about because mineral oils would make gaskets and seals swell and Synethetics didn't-and hence leaking ensued- This shouldn't be an issue with modern synthetics). A synthetics viscosity wont degrade as quickly and the oil wont evaporate under high temps like a mineral oil does.

The 0W number, in say, 0W-40- signifies the cold flow viscosity while the 40 is the viscosity when at 100 deg C.

The recommendations from Jaguar of old was 20W-50.

I cant find a 20W-50 with a Zinc and Phos level of 1750 ppm.

There's a 0W-50 but that's 0W flow at cold.

There's a 15W-50 synthetic with a 1200 and 1300phos and zinc respectively.

Im now wondering whether to relax my requirement for the cold whether viscosity. A thiner viscosity under cold oil temps actually helps the oil to pump around the engine better.

There is a 20W-50 oil for V-twins, and that has 1600 and 1750 Phos and Zinc resp. The only problem there is that it doesn't contain the friction modifiers that an automotive synthetic would have so the viscosity would degrade quicker over time. Will it degrade quicker than a mineral oil? I seriously doubt it.....

I may just try the 0W-50 because although its cold pump viscosity is light, it has high zinc and phos and I don't think that 0W cold visco is a problem- unless anyone here with a technical/engine durability/design back ground can comment on that?
"Live Fast, Live Well, Live Free!"
1970 Jaguar E type OTS

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Gfhug
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Location: Near Andover, Hampshire,in D.O. Blighty
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#5 Re: Gulf Classic 20-50 mineral oil

Post by Gfhug » Fri Jul 19, 2019 4:38 pm

Rex, that's very interesting. A popular oil in the UK is:
https://www.morrislubricantsonline.co.u ... r-oil.html

Can't see any obvious Zinc or Phosphorous levels:
https://www.morrislubricants.co.uk/prod ... 027604.pdf

Geoff
S2 FHC Light Blue

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Topic author
pmansson
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Joined: Sun May 16, 2010 8:31 am
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#6 Re: Gulf Classic 20-50 mineral oil

Post by pmansson » Fri Jul 19, 2019 8:29 pm

The Gulf oil, in the 5L metal can, has a zinc level,of >1600

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