I'm not talking a huge quantity. 10-15% unleaded on a fillup.
The paragraph below explains the difference between #1 and #2 diesel. Adding the unleaded just creates a slightly thinner fuel. It may not sound smart but the old man has owned at least one million mile truck(semi). He must be doing something right.
Fortunately, large truck fleets and petroleum marketers such as truck stops and wholesale fuel suppliers are capable of improving the winter quality of diesel by blending a lighter diesel stock, commonly referred to as No. 1 diesel, into the regular No. 2 diesel. They may also achieve positive results with the use of additives. In either case, they can save money and avoid potential down time by knowing the cloud point of the fuel before the blending or additive treatment.