Well, we bought our 2021 Mazda CX-30 brand new in January of 2021. It has the 2.5L non-turbo SkyActiv engine and a six-speed automatic transmission. It has 46,000 miles on it now and it's been a good vehicle for us. I took it to a shop yesterday to have a few things done. All I ended having done were replacing the spark plugs and the serpentine belt. They said that the other belt (for the A/C) was fine and still had a lot of life left in it. The owner's manual said that the spark plugs are supposed to be replaced at 70,000 miles and the turbo engine ones are due at 50,000 miles.

The old ones did not look too bad (photo attached). The spark plug in my lawnmower looked worse after month or two. Haha!!. I did notice that the car had a bit more pep when merging onto the highway with the new plugs installed. The serpentine belt did have a bit more wear on it than it should for the mileage, so I viewed it as cheap insurance by having it replaced. I kept it as a spare and will stow it under the passenger seat. I will have the A/C belt replaced at the next major service. What surprised me was that the independent shop said that the rear differential and the transfer case are "dealership only" items and that they did not have the proper type of oil that our car requires (kudos for his honesty).

He had the oil and the internal filter for the transmission in stock (Castrol TransTech or something like that), but suggested that I go to the Mazda dealer and have them check it BEFORE doing a drain and fill. He noticed a "shudder" from first to second gear that he felt when test-driving our car before working on it (as they always do). Our Mazda did that when it was new - but only once in a while. It's been fine overall and would just do it every now and then. My last two vehicles had a CVT (Nissan and Honda) which don't have "gears" like a traditional automatic - so they didn't have that issue. I still don't like CVTs, though. Our Mazda did the "shudder" thing again yesterday for me - once or twice - and for him too. The guy specializes in transmissions, so I shall heed his advice.
He looked on his computer and the automatic in the Mazda is said to have "lifetime" fluid in it - which is insane when you consider that there are moving parts, heat, friction or whatever. Even synthetic transmission fluid will succumb to pressure, heat and war eventually.

Our powertrain warranty is good for about four more months. He suggested going to the Mazda dealer and having them do the differential oil & transfer case and to log a complaint (for warranty purposes) with Mazda. He said that the transmission could still operate perfectly fine for 200,000 miles - even with the 'shudder' - but still suggested that it could be a problem in the valve body (I concur) and that it's something that the dealership might replace under warranty (5 years or 60k miles). He said that there is chance that Mazda will authorize the dealership to replace the valve body or even the entire transmission. I could live with the occasional 'shudder' if I knew that nothing else would ever go wrong with it.

While there yesterday, I had intended to have the brake fluid bled and replaced. He said that he didn't want to "take my money" and that the fluid still looked good and was not in need of replacement. He suggested that I wait until I had to get new brake pads - probably another 20,000 miles from now. So far, I have only had to add a few ounces of new brake fluid over the past 4+ years. He remarked about how spotlessly clean my car was and could tell that I took good care of it. That was nice to hear.

Has anybody else experienced the 'shudder' issue with a CX-30? It might be the only glitch in an otherwise excellent vehicle. Never had a any issues with it and it had two minor recalls in the first year, but our car never had any of the listed issues (tailgate and something electronic). We just paid it off in July and plan to keep it for several more years. I believe that it has a lot of life left in it.



The old spark plugs. Not too terrible for the mileage on them. Glad I did not wait until 70k, though.



The new spark plugs - NGK.

 

Your Mazda is not a CVT. The shudder you are experiencing may be normal because the ECU is adjusting the TCM shifting perimeters and sometimes it causes the transmission to be in a higher gear then the torque applied. If it happen all the time then that would be time to have Mazda look into it further.
The transmission in your Mazda is a hardy bult transmission that can really take a beating and last unlike fragile CVTs

The spark plugs are clean but showing a lot of heat transfer. Its normal and another sign that the spark plug should have been considered changing sooner. Without shing a bright light down inside to see the complete insulator it hard to tell complete information for reading spark plug. And that the engine was idled down before shut of changes the reading of them for normal engine speeds driving.

 

Oh, I KNOW that it's not a CVT. I have driven a Nissan Altima, a Honda Accord and a Honda CRV that each had a CVT in them. The Mazda CX-30 has a six-speed automatic. The transmission guy said that they act differently (and I know that - since a CRV doesn't have "gears" like a traditional automatic). The fact that he and my wife both noticed the 'shudder' without me having to say anything about it first let me know that something was up. The warranty expires at the end of January, so I wanted to "get it on record" that there was a potential issue.

UPDATE: I went by the Mazda dealership today and spoke to the service writer. I have an appointment on Wednesday (next week) to drop it off. They're going to give me a free loaner vehicle and see what they can figure out. At the very worst, they'll say that it is completely normal (I know better) or they'll have Mazda authorize some kind of warranty repair. They said they want to see if it's throwing any codes (it wasn't on my little scanner or the one at the independent shop). I wonder if the Mazda dealership would drain & fill the transmission fluid and replace the filter as part of a 'warranty' repair. If they have to order a new transmission, that would be a lengthy repair.

The dealership said that my differential and transfer case don't need to be done until 60,000 miles. That's the "big service" with the CX-30. I think a fuel injector cleaner service is due at 60k as well. We only have 46,000 on it now and - overall - we have been very pleased with our CX-30. We paid it off two months ago, which is a very good feeling!

Part of the reason I am skittish about the transmission is because my friend Kenny has a 2021 Chevy Colorado pickup truck with 70k miles on it. It began doing a 'shudder' and he said it sometimes felt as if he were driving over rumble strips. He took it in and the torque converter apparently went bad. Pieces of it broke off inside and it was making the entire transmission act weird. He has the extended 100k warranty, so they had to order him a brand new transmission. They don't rebuild them anymore, apparently. His truck has been at the Chevy dealership for A WHOLE MONTH, but they gave him a 2025 Colorado as a loaner vehicle. His had an 8-speed in it and, according to him, they don't make them anymore so they had to order a 10-speed for his truck and it has not arrived yet.

The 'shudder' is happening a lot more often than it used to - and that's what is concerning us. Keeping my fingers crossed, but I will know something on Wednesday. (FWIW, if they try to tell me that it is normal, I am going to ask them if I can drive a used CX-30 on their lot and see if it does the same thing. That way, at least I will have a good point of reference.)

 

I would not worry about your pump or torque converter. At your miles and knowing how they are manufactured unless you been power braking that would balloon the inside of the torque converter or drag racing then it’s really hard to damage those two parts.
Well the good news it that will find the problem and seems your cover under warranty. And your loaner might be a 2026 model to try out?

I wouldn’t compare your friends Chevy tranny to yours and the story is well unusual considering Those that know torque converters. But it doesn’t matter it not close to the same as a Mazda tranny .

Yes it is more cost effective as well it takes a qualified and experienced auto mechanic to not only have required specialized tool to rebuild a transmission then just to replace the complete transmission.

keep this thread updated it’s an interesting case would like to know the conclusions.

 

No drag racing, power braking or abusive driving. We did sometimes travel at high speeds on the Autobahn over in Germany, but that's not really anything that should affect the transmission. The EU-spec CX-30 uses a smaller (2.0L) engine with a six-speed manual being standard and with the same automatic transmission we have as being optional. My wife and I are actually fairly easy on cars compared to most folks.

I agree that our Mazda's tranny is nothing like the one in a Chevrolet Colorado truck - but the fact that his truck is the same model year and has been sitting at the dealership for a month now kind of spooked me a little bit. He has more miles, though. Anyway, I'll get a handle on this by Wednesday and we will see what they say at the dealership. if they try to tell me that it's normal and there's nothing wrong, I'm going to ask them to give me a new or used CX-30 on their lot so that I can drive it and see if it acts the same way. That'll be the best way to know if they're jiving me or not. Maybe it was something in the valve body; I don't know.

I'll definitely keep you posted as to what happens. Funny about the spark plugs. Mazda recommends the turbo 2.5 to be changed at 40 or 50k miles, but the non-turbo 2.5 (which we have) is supposed to wait until 70k for replacement. Glad I did not wait that long! Mazda recommends the transfer case & differential (ours is all-wheel-drive) be done at 60,000 miles - which is certainly understandable.

My wife's 2025 Toyota Camry hybrid goes in on Tuesday for its 10,000 mile service. The first service was just a tire rotation and this one is a tire rotation + an oil and filter change. That darn thing uses 0w8 motor oil. I never knew that there was such a thing. The maintenance for the first two years or 25,000 miles is free on it. The fuel mileage is 42 miles per gallon so far - which is darn good. That thing really boogies too.

Stay tuned, sir!!

 

Spark plugs are a subject often badly misunderstood and most use their supportive arguments based on the service recommendation set by the OE
A simple scope analysis proves the OE miles for service life are simply the extreme service life of them and not the best for the overall performance which include MPG.

Tailspin subject the reason Mazda and many use 0w30 primary suggested oil and also Toyota ow8 is to meet MPG standards. Without it the estimated MPG would be greater and effect sales and advertising negativity if they didn't come out with newer models improving MPG.
In the examples the thought of protecting the engine first by using the oil suited for the operating environment goes out the window. And again, this is a bad subject on forums because of all the opinions which is largely based on shallow testing of using other than the recommended viscosity oils.
May be why generally I only post what I use in my Mazda and why I choose the viscosity or even synthetic, semi synthetic or even conventional oils.
I will state the proper way unless the OE uses the exact wording REQUIRED choice of motor oil is directly affected by your operating environment and the intended use of the vehcle.

 

I normally do things a bit sooner / more often than the owner's manual or auto maker suggests. I know that changing plugs used to be very easy back in the day, but nowadays things are so much more complex than they used to be. Since I had them done at 46,000 (instead of the recommended 70k interval), I now know to do it sooner the next time - maybe around 80k. Since I am retired now, that's probably gonna be in another five years from now.

Regarding oil, Mazda recommends 0w20 synthetic - and that's what I have always used. I have heard people say that 5w30 is suitable in our climate (Virginia), but I figured that the 0w20 is fine, especially if I change it out between 4,500 and 5,000 miles (instead of 7,500 to 10,000). As you mentioned before, I believe that the 0w20 is called for in the interest of improved fuel economy. Auto makers are pushed very hard to raise their fuel economy standards, even if it potentially causes engines to wear out somewhat sooner.

Seeing as we just paid off this Mazda, I feel as if we have even more reason to do what it takes to keep it running well.

On an unrelated note, the Honda Accords my son and stepdaughter drive, the CRV my daughter-in-law has and the Mazda CX-30 all use the same oil filter. So did my old Nissan Sentra and Nissan Altima that I used to drive.

Stay safe out there in California!!

 

I dropped off our CX-30 today at the Mazda dealership. They gave me a new 2025 CX-5 as a loaner vehicle. It has 1,450 miles on it. Same 2.5L non-turbo engine as the CX-30 and - I assume - the same six-speed automatic transmission. This CX-5 is also all-wheel-drive like our CX-30.

I drove it about 25 miles today on the way home and it did NOT have any shudder at all. It's going to be interesting to see what they end up doing.& what they'll find with ours. Perhaps they can fix it with a 're-flash' to the computer. From what I understand, Mazda has had very few issues with any of their automatic transmissions in recent years. Let's hope it is something minor

Compared to the CX-30, the CX-5 feels like a bus. It's obviously roomier inside and all-wheel-drive comes standard (while it is optional on the CX-30). The same 2.5L engine has to pull a bit more weight. I think the smaller CX-30 looks better - but that's just my personal opinion. The CX-50 looks better than both of them, though. It has a more 'blocky' look to it. The CX-5 they gave us is an odd color call Platinum Quartz Metallic. Not something I would ever buy - but hey; it's just a loaner.

 

UPDATE:


I picked up our CX-30 this afternoon. They called me from the dealership this morning and said it was ready. Whatever they did, it is working.

They "reflashed" the computer that controls the transmission. It is supposed to "re-learn" and the shudder is expected to go away. They told me to drive if for 1,000 to 2,000 miles and to let them know if the problem comes back. The mechanic did notice the shudder and apparently fixed it quickly. They put it on a diagnostic machine and it was not throwing out any codes. I noticed an improvement right away and even tried to get it to shudder. It did it once - but never again. The shifts in the other gears seemed to be better as well, but I could just be imagining that. Nevertheless, the 1-2 shift is now pretty crisp.

I'll drive it a good bit and try to put on another 2,000 miles long before January when the warranty expires. Hopefully, I'll never have another issue with it.

They gave me a new 2025 CX-5 as a loaner vehicle - which felt like a bus in comparison to the CX-30. it was slower and less responsive (same engine, but more weight) than my CX-30 and on windy roads was not nearly as 'fun' as the more nimble CX-30. The CX-5 did have a lot more room on the inside, though. Both have the 2.5L non-turbo engine with the six-speed automatic transmission. The CX-50 sitting in the showroom was REALLY PRETTY. It's the same size as the CX-5, but is sort of blocky looking with more aggressive styling.

It seems a shame that Mazda is not selling the 6 sedan anymore. Rumor has it that they were going to offer it in the USA with a straight six engine mounted longitudinally, rear-wheel-drive or optional all-wheel drive. They were supposedly going to offer a manual transmission, but that's apparently only reserved for overseas customers. A redesigned 6 sedan with an independent rear suspension would truly be a poor man's BMW.

 

Did they suggest to also manually shift it a few times as well? If not, you should. Nice to read they cleared it up.