Mixing E-85 and Regular 87 Octane in NON-Flexfuel car for a cheap 93 octane... Will it work? (vehicle, 2012)
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This is something I never intended to try but I’ve always been curious about.
What would happen if you pump E-85 (108 Octane) and then mix 87 Octane at a ratio that it comes out between 91 and 93 Octane in a NON-Flexfuel car (or car that isn’t tuned for E-85) that requires Premium Fuel? Will it run? Will it have problems? Would you damage anything or would you just get lesser mileage?
Also what ratio would you have to mix in order to ensure the octane is 93?
This is something I never intended to try but I’ve always been curious about.
What would happen if you pump E-85 (108 Octane) and then mix 87 Octane at a ratio that it comes out between 91 and 93 Octane in a NON-Flexfuel car (or car that isn’t tuned for E-85) that requires Premium Fuel? Will it run? Will it have problems? Would you damage anything or would you just get lesser mileage?
Also what ratio would you have to mix in order to ensure the octane is 93?
Read this.
It’s important to make sure you’re only using E85 in a flex fuel vehicle. In a conventional fuel system, it can cause a lot of problems.
High alcohol content causes steel lines to corrode. That’s why the fuel lines in flex fuel vehicles are usually lined with nylon.
Conventional rubber connecting hoses and O-ring seals tend to dry out when exposed to E85. That can lead to fuel leaks.
Metals in the fuel pump will corrode. That means poor pump performance. Conventional fuel pumps typically last for about nine thousand hours. But put one in a flex fuel vehicle, and it may only work for about five hundred hours
E85 will also deteriorate a conventional fuel level sensor and float, causing it to malfunction.
E85 is ~108 octane. So, to get 87 E10 up to 93 octane, you'd need:
108 - 87 = 21 octane difference between the two. 100% E85 would increase octane by 21 points.
93 - 87 = 6 octane increase desired.
6 / 21 = 0.29, or 29% E85 would be needed. Let's round it off to 30% to make math easier.
~
Since 87 is already (up to) 10% ethanol, you'd end up with "E47" to get your desired 93 octane. This will be more corrosive of some lines than E10, but less than E85, obviously. More of a problem are fuel injectors and the fuel pump - specifically their flow capacity. Pure ethanol burns at a 9.0:1 air fuel ratio. To run E47 in a vehicle designed to run on 100% pure gasoline, you'd have an approximate stoichiometric ratio of ~12.0:1, or ~23% higher fuel flow rate. The fuel pump is likely up to the task, but not all injectors are oversized enough. This could result in the engine running lean and/or fuel trims going out of control under WOT conditions.
EDIT: I should also add that, while E85 may be cheaper, it has only 76,000 BTUs per gallon, compared with gasoline's 116,000. So, while you may pay more per gallon of 93, you can go around 20% farther than you could on a gallon of your E47 mix, or 32% farther than on E85. That certainly eats up some of the cost difference.
10 years ago I towed a car cross-country from So Cal to Wisconsin. Just before I hit the Midwest, my gas mileage decreased about 15%. On my return trip, the gas mileage returned to normal around Utah. Only after my trip did I make the connection the fuel in the Midwest contained ethanol.
If you want 93 octane that badly, mix regular with 100 racing unleaded.
The above answers had some great specifics, I thought I'd add a generality.
Your question covers two different areas.
How much ethanol effects mileage, (how the engine burns). After all, it's just diluting the high-energy gas with medium energy alcohol. Also, the E-95 or more E may have corrosion issues if the engine isn't specifically designed for that amount of alcohol. (See earlier comments).
Octane is a separate issue: The octane does NOT directly effect your Hp or mileage. Higher levels allow your engines to run hotter and still not knock. Most (all?) modern engines have sensors and computers that adjust the operation so you get the best result out of what you put in the tank, and therefor lower octane (cheaper) gas should be used unless it specifically says otherwise in the owners manual.
Example: My BMW 335i e92 with twin-turbos is specifically designed to run hotter than the average car, so a higher octane (mid-grade per the manual), will be sensed and used by it's computer to generate a bit more power, or better MPH, safely. Put that in a standard car and the car's computer wouldn't let the car run hot enough to damage itself, or benefit with more power/mileage.
10 years ago I towed a car cross-country from So Cal to Wisconsin. Just before I hit the Midwest, my gas mileage decreased about 15%. On my return trip, the gas mileage returned to normal around Utah. Only after my trip did I make the connection the fuel in the Midwest contained ethanol.
If you want 93 octane that badly, mix regular with 100 racing unleaded.
E10 has ~3% less energy per unit volume. I have access to both E0 and E10, and have every fill in a spreadsheet going back to 2012, and I haven't ever seen a mileage loss from E10 greater than ~3%. I can't say that would be the same for all vehicles, granted, but 15% is wildly outside of what I'd expect.
E10 has ~3% less energy per unit volume. I have access to both E0 and E10, and have every fill in a spreadsheet going back to 2012, and I haven't ever seen a mileage loss from E10 greater than ~3%. I can't say that would be the same for all vehicles, granted, but 15% is wildly outside of what I'd expect.
Did you, by chance, make this trip in winter?
Yeah. Butane in winter blend fuel plus aerodynamic drag from cold air will cause a big MPG hit at highway speeds. Particularly in something with lousy aerodynamics.
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