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Understanding Fuel Economics

The 70% Rule Explained

The 70% rule is a simple guideline for flex-fuel vehicles. Since ethanol contains about 30% less energy than gasoline, it should cost 30% less to be economically equivalent. If ethanol costs 70% or less of gasoline's price, choose ethanol.

Energy Content Difference

Gasoline contains approximately 114,000 BTUs per gallon, while ethanol (E85) contains about 80,000 BTUs per gallon. This 30% difference in energy content affects fuel economy and must be considered in cost calculations.

Environmental Benefits

Ethanol is a renewable fuel made from corn and other plant materials. It burns cleaner than gasoline, producing fewer greenhouse gas emissions and reducing dependence on petroleum imports.

Vehicle Compatibility

Only flex-fuel vehicles (FFVs) can use high-ethanol blends like E85. Regular vehicles can typically use up to E10 (10% ethanol blend) without modifications. Check your owner's manual for compatibility.

Factors Affecting Fuel Choice

Consider These Factors:

  • Price Volatility: Fuel prices change frequently; recalculate regularly
  • Availability: E85 stations are less common than gasoline stations
  • Driving Habits: Highway vs city driving affects fuel economy differently
  • Vehicle Age: Older flex-fuel vehicles may have different efficiency ratings
  • Seasonal Variations: Cold weather can affect ethanol performance

Maximizing Fuel Savings

Monitor Prices

Use fuel price apps to track local prices and switch between fuels based on current economics.

Efficient Driving

Maintain steady speeds, avoid rapid acceleration, and keep tires properly inflated to maximize efficiency.

Vehicle Maintenance

Regular maintenance, clean air filters, and quality oil help maintain optimal fuel economy with any fuel type.