1948 Mark IV 3.5 L Any Oil Type Recommendation?

Pre-XK
1

Does anyone have a good recommendation for the brand and weight of oil to be used
in the 3.5 Litre engine in my 1948 MK IV DHC? The oil presently in the car looks to have
a greenish tinge to it.
The owner’s manual had suggested MobilOil 30 and lots of other quaint names that are no longer available.
Thanks

2

Any 30 weight oil works fine in my experience.

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4

Thanks, Roger ! Any idea why the present oil is slightly green?

5

Some reasons why engine oil has green color tinge include,
1.) Some engine oils are green colored,
2.) Some coolant antifreezes are green and might have leaked into engine oil,
3.) Incorrect lubricant, such as green-colored Castrol hydraulic fluid.
No matter the claims of oil condition or appearance, I always change all fluids and filters at time of acquisition of any old car.

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6

I too have seen green new oil, don’t remember which brand. You can probably figure that oil has less than 1000 miles on it.
I use Pennzoil or Valvoline or Quaker State SAE 10W40.

7

Duckhams oils were green way back.

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8

G’day Everett, I have used Penrite Shelsley light or medium or Penrite Classic Medium in my 3.5 Lt MkV for over twenty years, and do high mileages. The reason for this is that these oils have a high zinc and low “detergent” content that better protects older engines. When I had the engine stripped down a couple of years ago (for other reasons), the rebuilder said the bores and pistons were in pristine conditions. If you can’t get Penrite, go for an oil with high zinc and low detergent level.

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9

Good also to ask about zinc in the oil. Zinc and phosphorus were added for copper and lead bearing corrosion control staring around 1942, at about 0.03% and rising to around 0.08% in the middle 1950s as high-lift camshafts came in use. A publication from Bob Olree of GM Powertrain Fuels and Lubricant Group says “Although break-in scuffing was reduced by using more phosphorus, longer-term wear increased when phosphorus rose above 0.14%. At about 0.20% phosphorus, the ZDP started attacking the grain boundaries in the iron, resulting in camshaft spalling.”

Most modern oils have zinc and phosphorus levels in the range recommended by Bob Olree, i.e. similar to what was in engines into the middle 1950s. Some, like Penrite Classic are just a little above the Olree-recommended limit, but not by much. As a recommendation, most modern oils have zinc and phosphorus levels comparable to original manufacturer specifications for the late 1940s and early 1950s. Modern oil manufacturers often post the zinc and phosphorus levels, ZDDP, for their products.

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