generally occupy a smaller footprint in the refinery the lower operating temperatures may also reduce emissions of co 2 and other gases in addition cavitation was found to produce a different yield slate than visbreaking specifically smaller amounts of naphtha and distillate were produced relative to visbreaking so recovery of these fractions may be unnecessary generally methods are disclosed herein for reducing the viscosity of a heavy hydrocarbon feed for use in a fuel oil the method may include subjecting a resid feed to hydrodynamic cavitation and thereby cracking at least a portion of the hydrocarbons present in the resid feed to produce a cavitated resid having a viscosity that is at least 50 less than the viscosity of the resid feed and preparing a fuel oil comprising the cavitated resid the fuel oil may have a viscosity less than or equal to about 380 cst at 50 u00b0 c as measured by astm d445 the fuel oil may also have a specific gravity of between about 0 96 and about 1 01 and can be measured by astm d4052 the fuel oil may also have a maximum sulfur level of 3 5 wt or less or 1 5 wt or less as measured by astm d2622 an embodiment for reducing viscosity of a heavy hydrocarbon feed which may be any of the feeds disclosed herein is illustrated in fig2 resid feed 100 is fed to hydrodynamic cavitation unit 104 under conditions suitable to crack at least a portion of the hydrocarbon molecules in the resid feed 100 and thereby reduce the viscosity of the resulting cavitated resid 106 cavitation may reduce the viscosity of the resid feed by at least 50 as measured at 50 u00b0 c the cavitated resid 106 now having.