Horrible gas mileage in brand new CX-5

[N7turbo]

There are too many variables between two people in different locations to make that comparison. Overall, I don't think wheel weight has a big effect on economy. Personally, I dropped 6.5 lb per corner and I don't believe I gained any fuel economy from it. The fuel economy differences between different tires is well known though.

 

[BoomerZoomr]

My 2025 CX-5 2.5L turbo is going through its first tank of gasoline. I have 36% gas remaining in the tank having traveled 181 miles of mostly highway driving. Not very good mileage, but the thing has to break in (I am hoping).

 

[BoomerZoomr]

Today I refilled my 2025 turbo CX-5 fuel tank with 93 octane. The previous tank was 87 octane the car salesman had put in. The computer indicated that my mileage on that first tank was 19.8, but the actual mileage by tank top-off was 20.8
Mostly highway driving, but around town I wasn’t babying it.

 

[leeharvey418]

Don’t even try paying attention to the mileage indication on the instrument cluster. It should come with a disclaimer saying “for estimation and entertainment purposes only”.

 

[Mazdiod2]

Today I refilled my 2025 turbo CX-5 fuel tank with 93 octane. The previous tank was 87 octane the car salesman had put in. The computer indicated that my mileage on that first tank was 19.8, but the actual mileage by tank top-off was 20.8
Mostly highway driving, but around town I wasn’t babying it.

I always get better gas mileage with the no-ethanol premium.

 

[RedBaron]

I always get better gas mileage with the no-ethanol premium.

Of course you do. But is it better 'enough' to pay for the increased cost per gallon?

 

[Mazdiod2]

I've never tried to calculate that.

 

[sm1ke]

I've never tried to calculate that.

I have, and I don't think its worth it for the mileage increase alone. With the 2.5T, it's worth it if you can take advantage of the other benefits it provides, like the increased performance at higher RPMs or if you have something like a JB4 piggyback tuner. With the N/A engine I would just stick to 87 from top tier suppliers.

 

[N7turbo]

I have, and I don't think its worth it for the mileage increase alone. With the 2.5T, it's worth it if you can take advantage of the other benefits it provides, like the increased performance at higher RPMs or if you have something like a JB4 piggyback tuner. With the N/A engine I would just stick to 87 from top tier suppliers.

Here we have options that include the same octane with and without ethanol. So there is no performance benefit, only your choice whether to take the cost savings per gallon of E10/15 or the increased range of the non-ethanol gas.

 

[Odrapnew]

Gas station by me had 91 No-Eth for same price as their 89 E10.
Their 91 E10 is more expensive than 91 No-Eth. Makes no sense.
I thought it was a mistake last summer, but it's been that way for over a year.
Another station near me has 91 No-eth for something like $1 more than 91 E10, which is what I expect.

Today I refilled my 2025 turbo CX-5 fuel tank with 93 octane. The previous tank was 87 octane the car salesman had put in. The computer indicated that my mileage on that first tank was 19.8, but the actual mileage by tank top-off was 20.8
Mostly highway driving, but around town I wasn’t babying it.

That first tank likely had a lot of idling, city driving, 'heavy foot' driving.
Don't pay attention to that one.
As you put more miles on it, MPG will increase as things break in and loosen up.
Check back in about 5000 miles.

 

[Mazdiod2]

I always fill the tank with the non ethanol when I get the chance, I guess it is solely for the increased range. I'm sure I would prefer non-ethanol for the same price as the E10.

Supposedly the price of ethanol is lower than gasoline, so it makes sense that the E10 is cheaper. But why do they charge $18 gal for denatured alcohol (stove fuel)?

 

[RedBaron]

But why do they charge $18 gal for denatured alcohol (stove fuel)?

Taxes?

 

[erhayes]

Because they can.

 

[BoomerZoomr]

@Mike2000z28 did your mileage improve on subsequent tanks?
I am on my second tank of fuel in my CX-5 turbo. The first tank was 87 octane (car salesman filled it) and my computer mileage was 19.8 mpg. At a quarter tank I refueled with 93 octane, so the blend in the tank is approximately 91 octane. Working through this second tank of gasoline, my mileage has jumped up 3 mpg with similar driving. The drivetrain breaking in probably accounts for some of that. I wonder though how much of the mileage increase is due to the engine being able to run more efficiently on higher octane fuel. Has anyone checked their mileage on 87 vs 93 gasoline? If you get better mileage on premium, it would offset some of the additional cost.
My actual (tank top-off) mileage on that first tank was 20.8 mpg, so computer was off by 1 mpg.

 

[N7turbo]

Mileage across most comments is the same between the two octanes.

However most people note the computer reports very low mpg from the first tank. I had the same experience.

 

[Mazdiod2]

Was the 93 octane ethanol-free? I always get better mpg with ethanol-free, no matter 91 or 93 octane.

 

[sm1ke]

I tend to get better mileage out of 93 in my CX-9. Not a lot, maybe an extra 15-20 kms (10-12 mi), but a bit more than 87.

 

[BoomerZoomr]

Was the 93 octane ethanol-free? I always get better mpg with ethanol-free, no matter 91 or 93 octane.

It wasn’t

 

[Mazdiod2]

It wasn’t

Then I guess it is because the Turbo is designed to run better on 93 octane. I think this has been documented before.

 

[propflux01]

I found on my 2024 turbo that after about 7000 miles the mileage went up quite a bit. I regularly see 27 on hilly, curvy 2 lane state highway roads now, where when new, I was lucky to get 22-23. You should manually check the mpg against the computer. In my case, this the first vehicle that the computer matches my manual calculations to a “T” over several calculations. Your short 4km trips are definitely not helping though. One thing I’ve noticed is slow acceleration really bumps it up. Around here it’s a race to the next stop light. I quit trying to keep up with the racers and it helped quite a bit.