I've not heard that.... one possibility is that the guy that told you your 3.0L was a V8 and not a V6 may actually be hiding under your hood, occasionally whistling a low note.

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2001 Ranger XLT 4.0L SOHC
Silver Frost w/ Dark Graphite interior


Modifications
Summit 3" Body Lift
31x10.50 A/T tires
Explorer overhead console
Explorer auto-dim mirror
Explorer auto-headlights
Aux1 & Aux2 inputs on factory AM/FM/CD/Cassette
Door-dinger silencer button
Seamless retractable roof and passenger-side ejection seat with steering wheel mounted controls and safety interlock