Mixing premium gas with regular gas probably won't hurt anything for the most part. It depends on your vehicle really. If your vehicle is a sedan that requires regular gas, the blend of premium and regular gas should have plenty of octane and detergent to spare.
It might even get a bit of better mileage or run a little bit better if you're lucky. However, if your ride requires premium gas instead of regular gas, the blend can actually reduce octane and make your vehicle run less efficiently compared to simply using pure premium gas.
More about Mixing Premium Gas with Regular Gas
- The Risk of Pinging: The majority of modern cars include computer controls to protect itself and to drive safely, so mixed gas should have little effect. However, older cars without these car computers might start pinging or the sound when the air/fuel mixture is igniting too quickly as caused by low-octane gas or a poorly timed motor. The solution to this is to top off the vehicle with premium gas until the octane is high enough to eradicate the sound.
- Mid-Grade Gas and Unleaded Mixing: For regular gas cars that benefit instead of suffer from mixed gases, you can possibly save more by using mid-grade gas instead of mixing premium and regular gas together in order to get to the same octane level. Furthermore, it's actually fine to combine different octane levels of gas as long as they're both of the unleaded variety. You risk car damage or more if you use "leaded" gasoline mixtures on your vehicle.
- Regular Gas Mixed with E85 Fuel: When you mix E85 fuel with regular gas, you're diluting the high-octane rating of E85. To be more specific, there's higher octane in ethanol compared to standard gas. As such, the more gas you add to the E85 the lower its octane becomes, which defeats the purpose of getting more octane. Because E30 gas isn't available at pumps, you have to blend E85 gas with 93 octane gas to receive the 70% gasoline and 30% ethanol ratio that's ideal for your vehicle.
- To Mix or Not to Mix: Some car owners mix, for example, 87s and 94s together for their Mercedes that requires 91-octane gas when it gets half-full. The question here is, "Is mixing regular gas with high-octane gas worth it?" Car experts claim that it's no real help finance-wise or performance-wise when you mix super premium gas with regular gas. Run one octane or another and don't bother wasting money mixing gases.