Q: Using E-85 or unleaded regular fuel.

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I unknowingly bought a 2013 Chev Silverado (4.8L) that requires E-85 fuel. However the owner's manual says I can use either that or unleaded. I plan to use unleaded. Q1: Will this hurt the engine? Q2: Was the rated estimated MPG based upon flex fuel usage and should it increase my power and performance by just using the unleaded?

Hello, Many of today’s engines are equipped to run on E85 fuel which is a high ethanol content fuel. The vehicle’s engine control module measures the amount of ethanol in the gasoline and adjusts the air/fuel mixture ratio on the fly depending on this alcohol measurement. 100% gasoline is mixed at a 14.7/1 air/fuel ratio, while E85 (85% ethanol, 15% gasoline) is mixed at a 9.8/1 air/fuel ratio. The car adjusts between these two ratios depending on the ethanol content of the fuel (which can range from 0-85%). You will be fine running regular unleaded in your truck as your owner’s manual indicates. The difference in fuel economy will vary depending on driving habits, altitude of where you live, outside air temperature and many other factors, however in most cases it will be very minimal. You will likely notice a bit more power by using the E-85 fuel however due to it’s increased octane. The real merit of the fuel is in two of its properties: its octane rating and its cooling ability. In either case your truck should run just fine with little noticeable difference.

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