I previously had a 2022 CX-5 Preferred non-turbo 2.5L and now have a 2025 CX-5 non-turbo 2.5L with 14,000 miles. I have no issues with the car, no warning lights on, fuel economy seems consistent with the economy I got in my old 2022. The only difference is I own this one where the previous was a lease.

I have noticed the exhaust is a bit stronger smelling in this 2025. I have no oddities at the tailpipe, oil level isn't dropping, no reason to suspect any issues. I have a scanner and monitored the fuel trims and have noticed my LTFT is always positive. Not much, just +5% on average and it doesn't matter if it just started or has been driving a half hour. It never goes below +3 and goes as high as +8 depending on load. STFT can be -30, 30, or anywhere between and bounces all around. I tend not to say anything to the dealer about fuel trims or anything I see in my scanner because I am not a certified tech. I don't know what I don't know and usually leave it there. As the smell is pretty strong I mentioned the smell to the dealer service advisor at an oil change and they went in back and came back with a master tech. The tech said it was normal, they all smell because modern catalytic converters aren't what they used to be and if there is no code there is no issue. Is it normal for these 2.5L skyactiv engines to run slightly positive LTFT at all times? I'm not about to run back to the dealer with what someone(s) told me on a forum but I am curious if others see the same. Thank you in advance.

 

They are normal and withing specification. there are so many reason why not to comparing to many differences between your 2 Mazda's as far as service related and use, non tested health conditions of either engine etc. Not sure about you but being certified up until last year to perform California Emission testing in an independent shop and a performance tuner for decades about the only since of learned skills smelling exhaust was either a F/I (fuel injection) system badly in need of service, a badly jetted carburetor or a engine with bad compression rings. Aside from that I need and still use an EGA(exhaust gas analyzer) to read the exhaust and measure the fumes. If you checked your I/M monitors and they are all in state of readiness then nothing is emission wise wrong with your engine, sensors ect., or ECU.

If you are concerned and it is still under WARRANTY go to Mazda and have them, check it out. Maybe, and I would do it "flash" your ECU if anything else courtesy for a concerned customer? But it is not required at all but you could ask for it if they don't volunteer it.

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