I would not run it UNLESS you find the oil spec. meets your required oil. I assume you are referring to engine oil. If you don't know or find that it does not meet your tractor's requirements, then change it and the filter before running it more.
Remember, the cylinder pressures inside a diesel engine are about twice the pressures of a gas engine - usually somewhere around 20 to 1. and the temps are much higher.
I don't like changing brands or types of oil in my tractor. I found a good oil and always use it.
If it is the correct oil, just the wrong weight - I would still change it to get the weight required for the temperature ranges where the tractor is used. Depends of how far off the weight viscosity is.