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19bonestock88 · 05-26-2018, 10:39 PM

Some “back of the hand” calculations to debunk this myth that adding diesel to gasoline(in a gas car) to gain economy...

Gasoline is 120,405 BTU/US gal and diesel fuel is 128,700 BTU/US gal, or ~11% more than gas...
Since the two fuels are formulated for the opposite forms of combustion, we’ll assume diesel has an “octane rating” of 0

If you mixed 5% diesel (for ease of math) into 93 octane, non ethanol fuel, you’d end up with a fuel that could be supposed to then have an “octane rating” of 88, which will run in most gas engines. Averaging the BTUs of the fuels, your new mixed fuel would contain 120,820 BTU/US gal, or 0.34% more than standard pump gas...

You’d have to be measuring your distance to the meter, and your fuel to the gram(or mL), in a controlled laboratory environment, to be able to maybe see any gain in efficiency from fuel alone, and this is ignoring any potential negative effects on catalyst efficiency, or the slightly enhanced lubricity of the fuel...

In addition, you’re now mixing 93 octane non ethanol fuel which I’m betting is at least a dollar more than regular unleaded, with on road diesel, which is usually on par price wise with premium unleaded, to make a fuel that no high compression or high boost engine will tolerate...

Can we call this myth, “BUSTED”, yet?

05-26-2018, 10:39 PM	#3 (permalink)
19bonestock88 Master EcoModder Join Date: Jun 2016 Location: KY Posts: 1,352 IGL - '04 Saturn Ion Team Saturn 90 day: 56.19 mpg (US) Thanks: 63 Thanked 366 Times in 269 Posts	Some “back of the hand” calculations to debunk this myth that adding diesel to gasoline(in a gas car) to gain economy... Gasoline is 120,405 BTU/US gal and diesel fuel is 128,700 BTU/US gal, or ~11% more than gas... Since the two fuels are formulated for the opposite forms of combustion, we’ll assume diesel has an “octane rating” of 0 If you mixed 5% diesel (for ease of math) into 93 octane, non ethanol fuel, you’d end up with a fuel that could be supposed to then have an “octane rating” of 88, which will run in most gas engines. Averaging the BTUs of the fuels, your new mixed fuel would contain 120,820 BTU/US gal, or 0.34% more than standard pump gas... You’d have to be measuring your distance to the meter, and your fuel to the gram(or mL), in a controlled laboratory environment, to be able to maybe see any gain in efficiency from fuel alone, and this is ignoring any potential negative effects on catalyst efficiency, or the slightly enhanced lubricity of the fuel... In addition, you’re now mixing 93 octane non ethanol fuel which I’m betting is at least a dollar more than regular unleaded, with on road diesel, which is usually on par price wise with premium unleaded, to make a fuel that no high compression or high boost engine will tolerate... Can we call this myth, “BUSTED”, yet? __________________ My current Ecotec project... My last Ecotec project...