2014 Mazda CX-5 - E85

Can I start using EA85 ethanol in my 2014 Mazda CX-5 ? If so, are there any special things I should do first? Driving a polluter bothers me so much that I try not to drive the car anymore and am considering selling it. But cars are expensive and I’d like to keep the Mazda if I can. It is otherwise a very good SUV. The window sticker said it would get 30mpg highway, but after 55,000+ miles and trying all kinds of ways to increase the mileage, it only gets average 22mpg with mostly highway driveng. I’ve complained repeatedly to Mazda dealer service, but they say all readings are good and nothing wrong with car. EA85 ethanol doesn’t pollute and is usually at least $1 per gallon cheaper than 87 octane gas.
If I can’t put EA85 in the Mazda, what cars can use ethanol in addition to gasoline?

Well THAT is wrong. E85 still emits CO2 just like E10 gasoline.

With E85, that will drop to about 16.5 mpg or so. That’s why its $1 cheaper. If the car is rated 30 mpg highway but only gets 22 mpg with you driving, the problem is you. The way you drive has a huge impact on the mpg’s AND a huge impact on carbon emissions. The simple fact you get 22 mpg instead of 30 mpg means you emit 25% more carbon dioxide.

If the owners manual says you can use E85 and the car has a sticker inside the fuel filler door, then you can use E85. If it does not and you use E85 anyway, you will destroy your fuel system and the car won’t run worth a hoot.

If you want to reduce your carbon footprint, walk or ride a bike, or buy a smaller car that gets better mpg’s.


Your five model-year-old Mazda has reached its depreciation plateau. Trading it in will cause you to “lose” some money, but it if you’ve paid it off you could trade it right now for a lease on a lease of a green crossover that emits dramatically lower emissions. Here is your current list of choices and those about to arrive. You could trade it for a pre-oned (used) Leaf or Bolt as well. Both zero tailpipe emissions. Why mess around? You sound very committed to the cause. And please tell me you don’t burn fossil fuels for heat, property maintenance, or cooking. Otherwise, you are starting at the wrong point in the carbon footprint and emissions reduction game.

The CX5 does not use E85. Do not put it in your car. To improve fuel economy, make sure the tire pressure is at the correct level. There is a sticker on the driver’s side door jamb that shows the proper pressure. It will be something like 32-psi. I like to put in 2-psi over so that it doesn’t get way under the recommended level when I next check tire pressure. How many miles on the Mazda? If the spark plug gap is too wide, that will affect gas mileage, too. Check your owner’s manuals to see when the plugs are supposed to be changed.


If there’s no badging on the vehicle that looks like this,

E85 gas can’t be used in the vehicle.

It’ll destroy the engine.



We had a flexfuel Plymouth Voyager and tried the E85 a number of times. The decrease in MPG kept it from being more economical than the usual 10% ethanol fuel.

It can be argued that the energy inputs in growing and transporting and fermenting and refining the corn that becomes E85 makes E85 a less efficient fuel overall than pure gasoline or E10 gasoline. Then there’s the unnecessary “mining” of topsoil to produce fuel, and the increase in the price of corn due to the higher demand.

Lots of pollution from making E85. Google ‘Gulf of Mexico dead zone” to read about one of the consequences of corn production.


E85 is poisen

Your 2014 Mazda CX-5 is not a flex-fuel vehicle.

Opening your owner’s manual for starters. Particularly the part on page 3-21 that says

"Your vehicle can only use oxygenated fuels containing no more than 10 % ethanol
by volume. Damage to your vehicle may occur when ethanol exceeds this

E85 is 85% ethanol. You can do the math on this one.

How did you manage to come to this conclusion?

Yes, but it’s energy content is much less. On flex-fuel vehicles (which your car is not) that can run on E85 fuel economy is dramatically reduced vs. gasoline. Usually on the order of 30-40% . So using E85 is at best a wash financially speaking in most cases.

Do you not realize that you are most likely using E10 now and it has 10 % Ethanol in it .

Hello Volvo,

Thanks for your reply. Yes I do realize that our current gasoline’s already have 10-15% ethanol blend in them. That’ why I was thinking it would be ok to use more ethanol in it.

My thinking was that if the fuel system o-rings and other parts are able to be used with ethanol that’s in gasoline, it should be ok with ethanol in general . Based on replies I’m getting I guess that’s incorrect.


Fuel economy is as much a matter of driving style and environment as it is mechanical fitness, so if everything checks out mechanically, I’d look to other factors, such as your driving style and the type of terrain you drive in.

I’m afraid your belief in the environmental benefits of ethanol are unfounded. When you consider how much fuel is burned to produce ethanol in the U.S., there is no environmental benefit, even if you ignore that burning ethanol produces carbon emissions.

In short:

-Unless your owner’s manual indicates your car is a flex fuel vehicle, you can’t use E-85 without doing damage.

-Flex fuel vehicles are no more environmentally friendly than other vehicles, even if you use E-85.

-Buying another car, especially a new car, does more harm to the environment than driving what you have, due to the environmental impact of manufacturing the car.

…so my advice is to keep driving what you have until it wears out, and then get an all-electric vehicle when it is viable.

No, it’s not 10-15%. It’s up to 10%. E-15 would harm many engines if it was being dispensed into non-flex fuel vehicles.

The PCM in a non flex fuel vehicle can not adjust the fuel trim enough to compensate for the difference in fuels. When the fuel trim reaches the limit of 33% the check engine light will illuminate, if you take the vehicle to a shop they will charge you $300 to drain the tank, that is if they are smart enough to figure out what you did before they start replacing parts like the mass air flow sensor and the oxygen sensors.

About 10 years ago when E85 was available at many gas stations in my area I used to drain E85 from customers non flex fuel cars once or twice a month. I would usually put the drained fuel in my own vehicle so it didn’t go to waste.


If driving a SUV bothers you, you should sell it. If you are worried about the environment, you should destroy it so someone else does not poison the environment with it.

As far as the lousy gas mileage, it is a small SUV. It is going to suck. The EPA mileage is going to be ideal conditions with 100% gas (not E10). The calculation was also likely done on a dyno, with no wind resistance. If you do your best and don’t accelerate hard, and don’t aggressively accelerate on hills, and coast, you can probably get close to as advertised. My wife’s 17 rav4 is well below the sticker rating because she typically drives 80+. When I drive it, I get several MPG better than she does. I have to cruise at 55 mph to get the highway mileage advertised.

As far as E85, E10, and 100% gas, these do not have the same BTU. 100% gas has about 114K BTU per gallon. E10 has about 111K BTU and E85 has a whopping 82K BTU. So unless your E85 is at least 28% cheaper, you are buying less BTU. Now this corresponds to at least 28% fewer MPG. So if you are currently getting 22 MPG, you should expect to get less than 16 MPG E85.

As far as it not polluting that is also a joke. It pollutes just as much as 100% gasoline. There is no free lunch in the gas guzzling SUV that you have.

I did a retrofit on a toyota camry to run on LPG (propane). Propane only has 91K BTU and my fuel economy dropped in my car from about 28 MPG gas to about 22 MPG LPG. So my 20% reduced BTU resulted in about a 21% reduced MPG. At the time, that was completely justifiable since my propane cost was over 70% less than gasoline. My propane cost was less than $1 per gallon (typically lower and as low as $0.69/gallon) when gasoline was over $3.25.