I run cheap 87 octane gas with 10% ethanol year round.
My 2004 300M base, gets about 18 in town and 25-26 on the highway. When the AC isn't running a lot (late fall through early spring), I can get 20 in town and up to 27 on the highway (rarely).
Mottman wrote:...The best fuel you can use is any grade WITHOUT ETHANOL ! If you can get it.
- "All things being equal" (which they rarely are), our cars should run the best on 100% gasoline as far as mileage goes. But, as Mottman said, it's hard to find 100% petrol any more. There was one station here in town who used to advertise it, but they've apparently switched to 10% ethanol over the last couple of years.
- Technically speaking, good-grade gasoline with a ethanol 10% content should give you a bit more HP and a bit worse mileage than 100% petrol, because that's how corn-based alcohol works compared to petroleum-based gas. (It's the "BTU thermal efficiency per volume"...or something like that.)
- If we ran 100% ethanol (which our system is not designed for), I think we would have about 30% more HP and 30% worse mileage on average. Again that is a ballpark estimate, working from my middle-aged memory. (I've seen the math and some tech articles behind that claim and it seems to work out in real-life assuming that the fuel you get is high-quality.)
- Down in Brazil they have multi-fuel cars, by law, that can run on 100% petrol or 100% ethanol. They can switch back and forth, depending on what is available. I think the cars down there can even now can automatically sense the fuel blend and switch without driver intervention. It used to require a manual switch over.
- Here, the Feds were pushing programs that gave rise to the "Flex Fuel" cars that can run on up to 85% Ethanol, but I don't know how well they work on the E85 stuff.
2004 300M Base - Black Lava Red