Kerosene

Start with that ratio, then watch the temps and performance. If you’re getting it free, I’d increase the ratio if it does not affect anything adversely.

You could always weigh it, lol. #2 Diesel weighs roughly 7.2 lbs / gal. Kerosene weighs roughly 6.8 lbs / gal.

Just to show an example JP-8 weighs roughly 6.7 lbs per gallon. JP-5 weighs 6.8 lbs per gallon and JP-4 (no longer used) weighed 6.4 lbs per gallon.

JetA (civilian jet fuel) roughly weighs 6.75 lbs per gal. JetB (civilian jet fuel) weighs 6.5 lbs per gallon. AVGAS weighs 6.0 lbs per gallon.

Now all weights are approximate. They can and do change dependent upon temperature, impurities, additives, etc...

Just in case anybody wonders why I memorized weights of fuel it is actual very simple. I spent 13 years in aviation. Quantity of fuel on board an aircraft is measured in lbs. a Sikorsky helicopter model 70 aka UH-60 Blackhawk, carries roughly 2,400 lbs of fuel on board when full. A Blackhawk has two181 gallon tanks with each tank having a one gallon sump that cannot be used. So you get 360 gallons of useable fuel. But to achieve that requires gravity fill. You get roughly 359 gallons of usable fuel when doing a pressure refuel (most common way to refuel) and 356 gallons of usable fuel doing closed circuit refueling.

And there ya have it folks. Now if you want to go over engine start procedures, join the military, lol.

Bruce K, re: Deutz 4 cyl Diesel engines. Used AIR COOLED Deutz engines farm tractors. We thinned diesel fuel with kerosene in winter. We also burned French fry oil, FILTERED drain oil, FILTERED mineral hydraulic oil. Those engines are still running strong 35 years later.