Conclusion
Does higher octane fuel make a difference on all vehicles? It did in this case. Because of VW's advanced electronics and highly adaptive engine management, the Jetta 2.5L has an elastic response to a changes in octane levels. Once we put in the 87 octane, we could feel the drop in performance-less responsive, less peppy, and overall just different. The engine instantly detected the reduced octane levels and adapted for standard performance. This analysis was based on more than 1,200 miles of driving over a week.

Switching between the two octanes allowed us to use the dyno to detect and confirm or refute any driving subtleties we noticed during the week. Even though the Jetta's gas tank flap advises 87 octane, the dyno graphs clearly show that running premium gasoline does have performance benefits including, a slight increase in fuel economy. In the end, you get what you pay for. If you want standard performance use standard gasoline. But if you want premium performance, pay for premium gas.

After the fuel tests, we couldn't resist adding at least one aftermarket performance part to the stocker Jetta. So we picked the most popular modification, an open-air intake. We chose Neuspeed's not only because of its steller performance reputation, but for the fact that the intake has been certified smog legal in all 50 states. The P-Flo intake took the Jetta to the next performance level by eliminating the airflow limitations in the stock airbox. Throttle response and power were significantly increased, plus the induction growl under the hood added to the sportier feel.

COSTS SUMMARY
91 OCTANE FUEL: .20/GALLON AVERAGE PREMIUM $.20
NEUSPEED P-FLOW $300.15
MSRP TOTAL $300.15
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