Your right on the age of the diesel engine, & the age of older tractors. I personally don't do anything to the diesel fuel I just run what they have at the pump, & it's sad to say I only fuel twice a year; So that would be late fall, & late spring I just make sure to change the fuel filter once year regardless of the hrs. used. I have never had any issues with the engine which is a 2018 Iseki 3 cylinder that requires low sulfur diesel. I might add that I always make sure the tank is full, & I never let it sit with just a 1/2 tank of fuel for more than 2 to 3 weeks, & I never have added fuel treatments.I have found that an additive and running #2 will still gel when it gets near zero. If you have a tractor made before they took the sulfur out of diesel you might worry about the lubrication factor. Anything made recently I think people worry too much about the lubricity of diesel. That said I probably wouldn’t run straight number 1. That for north they are almost certainly blending in number 1 so I’d just make sure you are getting recent fuel and you should be good.

Thanks I did NOT know that about increasing fuel consumption.Many years ago, as an engineer for Caterpillar, the smaller machines at our plant in Brooklyn Park, MN, needed to switch from Cat engines to Perkins rebadged Cat when Caterpillar bought Perkins. With the change, we found we couldn't pass our cooling tests. Perkins engineer over to MN to find out what could be the reason. He ran through our test parameters and learned we used fuel from the plant's supply. Being in Minnesota, the plant used a winter blend - half #1, half #2. Turns out that due to the lower heat content of #1, more fuel is used to reach peak power (needed for our cooling test) and subsequently more heat rejection into the cooling system. Add special tank for testing and easily pass our cooling test. It looks like you don't use that much fuel in a year so not a major problem but for those who think it is only a lack of lubricity, I'm sure you are aware that fuel usage with #1 is much higher, but did you also realize that your engine will need significantly more cooling?