I am planning on adding meth/water injection to control my EGTs. The truck will have 150 gallons of diesel onboard. How big do I need to make the meth/water tank? How do I calculate consumption per gallon of diesel?

 

W/M is an "as needed" situation, so figuring an exact quantity is not possible. If it were me, I'd go with 15 gallons. That's 10% of your capacity. You can always carry more, but I don't think you'll need it.

 

Looking at the tank sizes available for retrofit 15 gallons sounds like a safe number. Based on the extreme weight of my truck I suspect I will use the water injection more then a typical pickup. The truck weights 18k lbs empty.