Page 10 Advertisements Column 2

Sun (Auckland), Volume II, Issue 609, 11 March 1929, Page 10

quality that restrains that sneak thief of power the silent knock ** From the Latin: ad (ap), meaning added to; and potens, meaning powerful, appotenic: possessing increased power; said of a gas that, being stable to heat and high compression, will therefore neither audibly nor silently "knock” in a high compression engine. sa \ Plume, the appotenic Motor Spirit, being stable to heat and high compression, burns evenly and steadily when the charge ignites. Expansion follows this correctly-timed, combustion in a steady surge of power that pushes the piston down throughout the length of its power stroke. Incorrect combustion follows the use of a Motor Spirit that . lacks stability to heat. A chemical change takes place in the charge shortly after the instant of ignition. Flames rip through the unignited portion of the charge, causing either audible or silent knocking, and its propulsive power is wasted in violent, spasmodic expansion which the piston cannot absorb . A silent knock? Yes, a contradiction of terms ! To understand how a knock can be silent, let us see what the word “knock” refers to. When the spark “leaps the gap,” Motor Spirit vapor ignites .... it burns .... it expands. Some Motor Spirit vapors expand with such vibratory violence that an audible metallic “clink” is heard. This is commonly known as a “knock”— a word that expresses the audible result of a high degree of power loss. The lesser degree of power loss resulting fro less violent expansion is the silent knock referred to. It results from the use of a gas which, being unable to stand up to the heat of combustion, is silently filching your power .... for a knock, whether silent or audible, means that power is being frittered away. A silent knock may be the cause of a power loss you have sensed, but could not understand. . . It may be taking toll of your engine efficiency without you being aware of it. The corrective restraint for this stealthy sneak-thief,of power is Plume .... the appotenic Motor Spirit, with a pedigree of power reaching right back to the appotenic, heat-resistant crude from which it is distilled. . . . Try it in traffic and over those hills where the silent knock usually forces you to change into second. ... It is appotenic quality you want; here it is ! pLUME The appotenic Motor Spirit. / V Jh s tmt % 7a St**Oft off There is a Plume pump not far Drive up—fill up—and prove it to yourself. VACUUM OIL COMPANY Pty. LT D. No. 4 of a Serie*?