2024 CX-30 Getting very low fuel mileage

[kkotcat]

I picked up my new cx-30 turbo a few days ago, it's a small sample size as I only have 50 Miles on it.

With conservative driving, city/highway about 60/40, I've burnt through over 1/3 tank of gas, and the average is 14.9 MPG; is this something to report to the dealer??? My 2018 CX-5 could get 40 mpg on cruise control on the highway and around 32 MPG combinded,

Is this a known issue before the engine breaks in?? I can't drive a car that only does 15 MPG, INSANE,

 

[Lazy2.5]

Wait to see what that number is after a tank or two of gas. You could also work on refining your driving style further, as that's quite a continual and long-term process which would involve ignoring other drivers wishing for you to speed up, lol. Assuming your CX-30 is AWD, that with the turbocharged engine won't be very fuel efficiency friendly.

For reference, when my 2015 Mazda 6 NA was new, it's first tank achieved 600km on 50L of fuel. That's about 28MPG, fairly conservative driving, city highway mix, and did not improve much.

Fast forward nearly 10 years later, the car has recently hit 200,000 miles, is tuned for 91 octane, and I quite consistently average 43-45mpg, significantly better than the EPA estimate, although this is mostly on open roads and being quite conservative.

In short, have some patience, as 50 miles of driving won't accurately put mpg into perspective, and consider a different car if you need better efficiency. An AWD vehicle with a turbocharged engine isn't it.

 

[N7turbo]

Yes. Many people report poor mileage from the first tank. My reading was also very low.

 

[sm1ke]

Starting from a full tank, run it down to almost empty, then hand calculate your mileage. The onboard calculator improves in accuracy the more miles it has to calculate from in that trip. When you reset the trip counter, it starts from scratch, so it can only work with the data it has.

 

[Lazy2.5]

Starting from a full tank, run it down to almost empty, then hand calculate your mileage. The onboard calculator improves in accuracy the more miles it has to calculate from in that trip. When you reset the trip counter, it starts from scratch, so it can only work with the data it has.

I find that my avg fuel economy read out consistently reads that I am using more fuel than what I hand calculate. By maybe .2-.3L /100km.

 

[kkotcat]

Thanks everyone for the info. Much appreciated. I'll run the tank to near zero and fill it up with mid grade or premium. I've been driving VERY conservative, not gunning it or anything, just treating it like a baby.

Let's see....but if 15 mpg continues I'm going to raise hell.

 

[clownshoes2]

Thanks everyone for the info. Much appreciated. I'll run the tank to near zero and fill it up with mid grade or premium. I've been driving VERY conservative, not gunning it or anything, just treating it like a baby.

Let's see....but if 15 mpg continues I'm going to raise hell.

You have 50 miles on a brand new car, with nothing in the computer, prolly bad gas from the factory, and most likely a heavy foot because the car is new. You're not going to keep getting 15MPG. Fill up with good gas, reset the trip and fuel monitor and go from there. C'mon man, use your head as more than a hat rack...

 

[clownshoes2]

FYI, I just did a road trip from Canuckistan to Ohio and back and I did around 35-38MPG.

 

[200955]

I picked up my new cx-30 turbo a few days ago, it's a small sample size as I only have 50 Miles on it.

With conservative driving, city/highway about 60/40, I've burnt through over 1/3 tank of gas, and the average is 14.9 MPG; is this something to report to the dealer??? My 2018 CX-5 could get 40 mpg on cruise control on the highway and around 32 MPG combinded,

Is this a known issue before the engine breaks in?? I can't drive a car that only does 15 MPG, INSANE,

That is absolutely dismal mpg even if the engine is not broken in yet. Either your hand claculator needs attention or something is severely wrong. Newer engines are built to tolerances that don't really need breaking in like the engines of 50 years ago. I'd demand answers from the dealer. Perhaps your mileage indicator in the cluster is trying to calculate and calibrate if that's what you are using for a reference. You didn't state the engine size but my classic car with a 512cu.in stroker engine gets 18.5 mpg in the city and 26 on the highway. Somethings amiss here. Let us know the outcome please.

 

[youri]

He had only driven 50 miles, out of those 50 miles the car might have idle for a while at the dealership during the sales and car explanation process, which would absolutely kill the mpg calculations. Nothing to worry about, that distance is too small of a sample.

 

[200955]

I am not familiar with the instrumentation on a CX 30 but my 2018 CX 5 shows "liters per 100Km" and currently it reads 7.2 ( much better than yours). It also reads out the distance I can go on the amount in the tank and both of these numbers have been fairly accurate since I purchased it. So perhaps the data you're using to calculate mileage is bogus based on what you use ( gauges or fuel volume) for an outcome. I, in no way, accept your car as getting 14.9 mpg even if you were driving uphill all day. The 2024 Mazda CX-30 is rated for up to an EPA-estimated 22 MPG city and 30 MPG highway—or up to 25 combined MPG's, a turbo model even higher yet. I would certainly be asking some questions at the dealership if you are certain that your calculations are correct.

This is what "clownshoes2 said in a post on Aug 2024:

Just got back from a day trip to Syracuse with the Fam Jam. This thing gets awesome gas mileage.
6.7L/100km, that's a whopping 35.1MPG average for the trip. 87 octane with quick fill up of 93octane at the Loves in Watertown.Cruising speed was just under 80mph. This thing is great! Heading to Ohio soon so I'm really going to push this and see how many miles to a tank I can get.

 

[njaremka]

Sounds like you're reading your fuel economy numbers from the on-board mpg display? The correct method is to hand calculate based on mile driven per tank and how many gallons at fill up. I imagine you'll get vastly different numbers performing the hand calculation.

 

[Lazy2.5]

Sounds like you're reading your fuel economy numbers from the on-board mpg display? The correct method is to hand calculate based on mile driven per tank and how many gallons at fill up. I imagine you'll get vastly different numbers performing the hand calculation.

the onboard computer is mostly accurate.

 

[jadmt]

the onboard computer is mostly accurate.

on my 2023 cx5 turbo the onboard computer normally reads up to 3mpg low compared to hand figuring. ie if my onboard computer shows 27mpg hand figuring will show 30mpg. I have 30,000 miles on it now and it has been that way since day one.

 

[Mazdiod2]

on my 2023 cx5 turbo the onboard computer normally reads up to 3mpg low compared to hand figuring. ie if my onboard computer shows 27mpg hand figuring will show 30mpg. I have 30,000 miles on it now and it has been that way since day one.

I have noticed that computer readout lower than my hand calculated mpg a couple of times myself. I mostly rely on the computer to compare the mpg on different routes and speeds, as I think it's probably at least consistant.

 

[Lazy2.5]

on my 2023 cx5 turbo the onboard computer normally reads up to 3mpg low compared to hand figuring. ie if my onboard computer shows 27mpg hand figuring will show 30mpg. I have 30,000 miles on it now and it has been that way since day one.

I've noticed the same. Mine will consistently read .2-.3L/100KM higher than the actual consumption, so while not perfectly accurate, it is close, and consistent, so still quite useful.

It seems to be inaccurate specifically in scenarios where road conditions cause engine load to increase, demanding a slightly higher throttle input (Such as climbing a small hill.)

 

[Mazdiod2]

I also have a Scangauge plugged into the OBDII port and it doesn't really completely agree with the onboard computer MPG either.
Just one of those things, like needing 5 quarts of oil instead of 4.8 qts for an oil change

 

[N7turbo]

Just one of those things, like needing 5 quarts of oil instead of 4.8 qts for an oil change

I think that's different. My current belief as to the source of the discrepancy is:

How much oil to the half-way mark
vs
How much oil to the full mark

I'm in the "fill to half-way between the two marks" camp. And indeed, when I do that, it takes a little over 5 qts for my 2.5T, which agrees with the manual for a drain and filter replacement.

Could always be wrong, of course.

 

[jadmt]

I think that's different. My current belief as to the source of the discrepancy is:

How much oil to the half-way mark
vs
How much oil to the full mark

I'm in the "fill to half-way between the two marks" camp. And indeed, when I do that, it takes a little over 5 qts for my 2.5T, which agrees with the manual for a drain and filter replacement.

Could always be wrong, of course.

me too right between the dots. takes 5.2 qts and so far in 30,000 miles has not burned any between 5000 mile changes.

 

[njaremka]

I never put any faith in those on-board fuel economy readouts. I always view them as "interesting to know" tidbits. Probably only good for "miles to empty" information.

If you are at all interested in actual fuel mileage, the hand calculation using tank fill up gallons and trip miles will be the most accurate.