For a JAWA motorcycle from 1975, it is recommended to use a high-quality engine oil with the appropriate viscosity grade. Since JAWA motorcycles from that era typically had two-stroke engines, you would need to use a specific type of two-stroke engine oil.
Two-stroke engines require oil to be mixed with the fuel in a certain ratio for lubrication. The specific mixing ratio can vary depending on the exact model and specific requirements, so it's important to consult the owner's manual or seek advice from a reputable JAWA motorcycle expert.
When selecting a two-stroke engine oil, you should look for oils that are specifically formulated for motorcycles or two-stroke engines. These oils typically have additives that help provide proper lubrication and prevent excessive wear. It's best to choose an oil that meets the manufacturer's specifications or recommendations.
To ensure you have the correct information for your JAWA motorcycle from 1975, I would recommend reaching out to JAWA or a JAWA motorcycle enthusiasts' community to get specific recommendations for the appropriate two-stroke engine oil and mixing ratio for your particular model.