Since a 275 gallon oil tank holds at most 250 gallons, and you should reorder at 1/4 tank (68 gallons), we can take 250-68 = 182 to determine how much heating you can use between fills. 182 gallons, at 5.2 gallons per day, will last for approximately 35 days, or just over one month. 9. What Happens When You Mix Red and Green Diesel. There are no issues with mixing the two types of diesel fuels, although red usually has a higher sulfur content than green. Also – it’s called green fuel because it’s eco-friendly. It’s actually either light green or clear in color. 10. How Long Does Red Diesel Stay In Your Tank? The test measures how much gum and sediment will be deposited after keeping the fuel at 95°C in the presence of oxygen for 16 hours. It roughly corresponds to one year storage at 25°C. A result of less than 20mg/L of sediment and gum after the test is considered acceptable for normal diesel. ACCELERATED AGEING. qmbO7Vh.