Oil

That varies according to climate and the salesperson you are talking with. The viscosity, meaning how thick or runny the oil is, will be listed on the oil cap or in the owner's manual. It will also list a rating such as "SH" or "SJ". The "S" stands for spark ignition, meaning a gas engine. As the refinements become more stringent, or improved additives are required, the second letter will increase by one. An older engine might require "SD" oil, or better. That means oil rated "SE", "SF", "SG", etc, is better than what is required. If you buy your oil from an auto parts store or any store with high turnover, you will get the highest current rating without even needing to look for it. Once a newer rating comes out, oil with the older rating is no longer produced.

As for brands of oil, they all must do the same thing. There can be some differences in the formulation of the additives, but beyond that, the most expensive oils are typically those that advertise the most. What most people find is whatever brand they use, they have the best luck when they stick with it. When you switch brands all the time, a detergent in one oil might not be compatible with the seal conditioner in the old oil. The dispersal in the new oil might not pick up the remnants of the old anti-foaming agent laying in the pan, to be carried to the oil filter.

The cheapest oil that meets the ratings requirements is satisfactory for your engine. What is considered to be the "best" depends on who you ask. Some people consider synthetic oil to be better than petroleum-based oil, but even that is debatable. If you have a very small leak, synthetic will leak out a lot faster. Manufacturers advertise that synthetic oil does not have to be changed as often, but oil is oil. It is the additives that wear out, and the contaminants that we want to drain out. Contaminants, mostly from blow by, accumulate at the same rate regardless of which type of oil is used.

There have been a few engines over the years that absolutely can not tolerate ignoring the oil change intervals, regardless of which brand is used. I have not heard that about your engine. My recommendation is to use a brand that is readily available, and stick with it.