Quote:
Originally Posted by Werner
Hello.
I am not sure if I have understood the core question correctly.
For vintage cars, a low viscosity can have the disadvantage that the shaft bearings leak leaking oil. Otherwise, a multi-grade oil is always better than a single range.
The most important is the API classification. Because of the non-ferrous metal compatibility. You should not go higher than "SC". Petrol engine oil API SC has anti-corrosion inhibitor, detergent cleaner, HD heavy duty additives. That is enough!
However, the oil still has to be changed many times (max. <1000 miles) because it runs without a filter and only then can the abrasion chips be
taken out.
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From what I have read, not an expert.
One major reason for using multi grade oil is a large portion of wear occurs during motor warm up until the oil/motor is at operating temperature. Straight 30 weight thickens considerably at colder/cooler temps. A multi-grade like 10w30 will thicken to what a straight 10 grade oil thickens to at a cold temperature.
A lot of motors when the temp in late fall/early spring/winter do not warm up all the way unless using a thermostat or if partially blocking the radiator. So the straight weight 30 oil is thicker than ideal all at all times.
Use of a magnetic oil plug can catch quite a bit of the metallic bits that might be floating around in the oil, but if you are especially concerned about this the motor can be converted to an oil filter system. The figure most mentioned here is changing oil every 500 miles. Oil is cheap compared to chances of premature motor wear.