Ah oil, an interesting and remarkably detailed subject. The science geek in me loves it
As always, read the owners manual. You can infer a lot by what its says. No need to use brand specific oil, but if it says use 10W30, use whatever top quality oil you're comfortable with. Do not buy cheap oil! You get what you pay for. The marginal cost of top quality oil in a tractor is nothing. That's why I use synthetics for all my outdoor power products. If you want regular oil, get name brand stuff, and read the label for the specs. You owners manual should say SM/CF or something like that. Don't use any oil below the spec they say.
Now, 10W30 means in cold temps it behaves like a 10W, ie flows easily, but in hot temps it behaves like a straight 30W, ie doesn't thin out when hot so it protects better. This opposite to physics. Cold molasses is thick, hot molasses is thin. How does the oil do the opposite of how God made the earth? Science. Chemical additives called VI additives or viscosity improvers. When hot, they molecules change shape making the oil behave as if its thicker than it really is. Works great, for a while. Then the VI additives break down, and the oil slowly becomes a 10W25, 10W20, 10W15, etc. The light chain actual-oil molecules also "boil off" leaving you with thicker oil outside what the VI additives do. That's why old OPE spec'd straight 30W, if used only in summertime. Less sludge in the crankcase, better lubricity as more VI means less lubricating oil for the same volume. Petroleum oil is a soup, a mixture of many kinds of straight chain molecules of variable length. It's a carbon backbone with variable type of hydrogen atoms attached, therefore called hydrocarbons. Aliphatic hydrocarbons mean straight chains, aromatic hydrocarbons means in a circular-type structure, like benzene. Long chain hydrocarbons are wax, short chain hydrocarbons are light machine oil. That's why at -35 cars won't start, because the wax in oil solidifies, and won't flow. When hot, short chain hydrocarbons "boil off," meaning oil is consumed. Ever notice on a long hot summer trip the car engine uses more oil than usual? That's why.
Downside to straight 30W is longer time to get the oil flowing when it's cold. Therefore, more metal to metal wear before oil pressure comes up. Not a problem if only used hot, big problem if used in northern winters.
So use whatever you like, just change regular petroleum oil right on schedule. For the small cost, changing sooner is also reasonable.
