Mid Grade Gas Seems Not As Good

[jrod81]

So, there is a gas station in town that gives Mid Grade gas at the Regular Grade price on Mondays. We have been filling up every Monday. We were getting around 45MPG and now since the switch around 41MPG. Anyone else had the same experience? Any reason why I shouldn't be putting mid grade in the Hybrid?

[sgtpruitt]

So you were putting regular in at the same station or you switched stations altogether?

I'd say it the gas station at first thought.

[JoePa]

I say your car is tuned for 87 octane so putting in a higher octane is running fuel that your car is not designed to use. So that could explain the small drop in mileage. However, there are many contributing factors that could explain it. Winter blend gas, you drove it a bit harder than normal, etc.

[tbone]

To answer your question, your car is designed to run on 87 Octane. A higher grade of gasoline won't improve power or gas mileage unless your vehicle has a high compression engine, like an SI. Using a higher grade of gas in some cars designed for regular 87 gasoline can give you less power and mileage although most of the time it shouldn't really effect anything other than the amount of money left in your wallet after filling up.
Switch back to regular and your gas mileage should improve. Even though it's a deal getting mid-grade for the same price, it's really just a waste in your vehicle.

If you're mileage is the same after the switchback, it could be the cold weather and/or changed driving styles as mentioned by JoePa.

[ryker]

Some high octane fuels use a % of ethanol to increase the octane rating. Ethanol has a lower BTU energy content thus it will get less MPG.

also the weather is getting colder. Cold weather cause the tire pressure to decrease. Decrease in tire pressure = increase rolling resistance = less MPG.

[giantquesadilla]

The HCHII is designed for 87 gas. Higher octane gasses contain less energy, resulting in decreased FE.

[adk]

Some gas stations use pure gasoline in 87 octane gas and put 10% ethanol in the mid grade. This could be part of the problem.

[truflip]

Not sure about hybrids but I get better FE with higher octane.
However, the price of higher octane gas cancels out the better FE.
Also the winter blends have a sometimes a huge impact on FE depending on the station