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MOTION
Magazine
Investigative Report |
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| By now you've been bombarded with ads trying to convince you to buy
a new gasoline called Shell Velocity. Supposedly, with Velocity in
your gas tank, you will experience smoother running of your engine and
improved acceleration. The catch? It's about P0.50 per liter more
expensive than our ever-more-expensive unleaded. You may not expect the
seas to part before your vehicle but you would definitely want more for
your money.
Do you really need Velocity? Does it deliver what it promises? Or are you just paying more for the same performance? Motion goes behind the marketing hype to uncover the truth. We are also presenting the partial results of our ongoing Velocity-user survey Click here to particpate in the survey Shell Velocity is an unleaded gasoline being sold by Pilipinas Shell. It reportedly differs from other gasolines in the three main characteristics of gasolines: octane level, volatility, and additives/detergents package. Octane The octane rating is the measure of a gasoline's resistance to premature detonation within your engine. This premature detonation can be heard as a pinging or knocking sound, particularly when accelerating or going uphill. This can lead to overheated and, eventually, damaged pistons, valves and spark plugs. Octane ratings are arrived at using a laboratory test engine. Pure isooctane, which is resistant to knocking due to its highly branched chain structure, was arbitrarily assigned an octane rating of 100, while n-heptane, which knocks easily, a rating of 0. A 95-octane gasoline has the knock resistance of a 95% isooctane and 5% n-heptane mixture. The octane rating required by your engine is listed in the owner's manual of your car. Normal unleaded is rated at 95 octane, while Velocity is 97 octane. EFI engines usually have knock sensors and compensate for a lower octane rating by retarding the engine timing to avoid knocking. However, power and acceleration will be reduced as a result. For engines with carburetor, octane rating can even be more critical because of the lack of a knock sensor and automatic computer compensation for a lower-octane fuel. If you are using a lower-octane gasoline and your engine knocks, you might benefit in switching to Velocity. Take note that there are other factors that can cause knocking:
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