2021 oil, 1959 engine? Nash Metropolitan 1500

Angstrom42

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If you do buy a new one, do some research on parts quality...a lot of what's available for old British vehicles, engines in your case, is astoundingly craptastic.

Oh, absolutely. I appreciate the warning, and its a solid reminder for others who may be following along as well.

I've spent quite a bit of time in the air cooled VW world so I'm very familiar with criminally negligent parts quality and shady vendors. It's phenomenal how quickly ACVW parts were able to "race to the bottom" but that community kinda did it to themselves... its a big reason why I don't have my 1965 Baja anymore. At least in brit car land there appears to be some old school vendors who seem to have their heads screwed on correctly.

Oh, and for oil pressure gauges, there are many options and new Smiths are available. I prefer mechanical, but whatever you do, don't use the late MGB setup w/ the excessively dampened senders....
Yep! The ubiquitous "Smiths Safety Gauge" is high on my list of things to acquire. Installation for the water temp bulb might get a little weird as they did something odd with the sender hole in the head below the thermostat for the Nash motors compared to the MGBs, but I'm sure an adapter exists. And if not, I'll make one on the lathe. (y)
I have an alternate view. I would recommend a Motorcraft semi-synthetic 5W20 to start with. It is a mixture and will have the attributes of a mineral based oil and the better cleaning capabilities of a synthetic oil. All modern rated oils are "backwards" compatible to all previous API ratings so no worries about using a newer oil in an older engine. Just do not run at high engine loads at first and after all it is cooler now. Let the oil pressure guide you as it says in the owners manual. There is no better way to determine the appropriate oil grade to use.

This thinner oil will get to more areas in the engine and help clean them out. Also, if the oil ways are partly clogged you would have a false high oil pressure even though the flow may be very limited. When the car was new even a straight 30 grade oil sheared down to a 20 grade so it should not be too thin. Many "engine cleaning" oil treatments are thin.

Ali
A very good point, and I like the logic here.
For my initial flush after reassembly, I picked up a 5q jug of the cheapest oil on the shelf at the FLAPS, which happened to be 5Q of a private labeled 5W20. I wanted to make sure it was thin enough to pump up and flow immediately, then grab anything else that might be floating around in the motor. Again, this was purchased with the intent to flush stuff out and then immediately change it, so the $13 jug of house brand seemed appropriate. I'll also keep an eye on oil pressures while doing this, of course.
 

SR5

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When the car was new even a straight 30 grade oil sheared down to a 20 grade so it should not be too thin. Many "engine cleaning" oil treatments are thin.
An SAE30 monograde should not shear down to a 20 grade, as monogrades have no polymer viscosity index improvers (VII), and it's the VII that shears due to mechanical stress, not the oil itself. I assume that is what you mean by a "straight" grade oil.

Of course fuel dilution is a separate issue.
 

Angstrom42

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An SAE30 monograde should not shear down to a 20 grade, as monogrades have no polymer viscosity index improvers (VII), and it's the VII that shears due to mechanical stress, not the oil itself. I assume that is what you mean by a "straight" grade oil.

Of course fuel dilution is a separate issue.
I believe what AEHaas was referring to in this comment was not modern oils, but instead the behavior of 60+ year old "SAE30" formulations. I assume these were blended from base stocks of raw crude with a dash of whale oil, bitumen and asbestos for color and flavor ;)
 

SR5

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I believe what AEHaas was referring to in this comment was not modern oils, but instead the behavior of 60+ year old "SAE30" formulations. I assume these were blended from base stocks of raw crude with a dash of whale oil, bitumen and asbestos for color and flavor ;)
The old oils had less refined bases, so oxidation was a problem, but I still can't see shear as being an issue.
 
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An SAE30 monograde should not shear down to a 20 grade, as monogrades have no polymer viscosity index improvers (VII), and it's the VII that shears due to mechanical stress, not the oil itself. I assume that is what you mean by a "straight" grade oil.

Of course fuel dilution is a separate issue.
Yeah if he meant that a monograde oil mechanically shears then add that to the long list of stuff he does not understand.
 
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I actually performed many experiments back then. One thing I found was that several brand name motor oils were a grade or two below what was labelled on the can from the start, before it went into the engine. 'Very disappointing. One multi viscosity 10W40 top oil brand came out of the can as a 20 grade oil. I thought it might be even thicker than advertised as it was specifically "Formulated for Turbo Engine Use." I was wrong. I never used that brand even though it was one of the top sellers of the time.

If I remember correctly all the oils I tested, single or multi grade, thinned with use, at least at first. I did no chemical testing so I cannot say if fuel dilution was the main issue but that makes sense.

ali
 

SR5

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I actually performed many experiments back then.
So you were testing oils back in 1959?......May I ask how old you are (if it's not rude, or too personal) and how did you test these oils for viscosity back then?
One multi viscosity 10W40 top oil brand came out of the can as a 20 grade oil.
Yes the early multigrades were known to shear, especially 10W40, but not monogrades as they have always been shear stable.

If I remember correctly all the oils I tested, single or multi grade, thinned with use, at least at first.
I certainly believe you on the multigrades, just not the monogrades. Nothing personal, it just goes against everything else I have read.
 
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66. I tested oils in the late 1960's and 1970's using a cheaper viscometer. Did not pay attention to model/brand but viscosity is easy to measure. Maybe not to the current standard but comparing viscosities was accurate. Again, I am not sure of the mechanism mono grade oils thinned. Just that they did thin (early on - later thickening no doubt from oxidation). Again, fuel dilution is the likely cause.
 
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Carburettors, manual chokes, there was sure a lot of unburnt fuel around. Also, here at least, it was rare to see a car with over 100,000 miles on the clock...they just didn't get used enough to burn off that fuel.
 
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I had a 1964 AH sprite with a similar but higher output engine. I ran 10W-40 in it from new to 55,000 miles. No issues with lubrication, just clutch cables, radiator hoses, freeze plugs, broken axles…something about once a week.
 
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