I reviewed the owner's guide on-line. Too cold - Brrrr!! - to walk out to the car tonight to get the paper one out of the glove box. There is a 40,000-mile spark plug change interval for the 2.5T and a 75,000-mile interval for the 2.5L non-turbo (which is what we have) in our 2021 CX-30. We have 38,500 miles on ours now and it's running great.

I didn't see anything in there about the interval for the transmission fluid. I know it doesn't need done anytime soon, but it's just good to know ahead of time when it needs to be done. Apparently, the coolant is good for ten years or 120,000 miles - which seems like a very long time to me. Can't believe that next week will be four years that we have owned this car. Our first Mazda - and it's been pretty decent overall.

Zoom! Zoom!

 

The transmission pan drop and filter service should have been done no later than 15k miles .
The coolant while it may go that long ,chemically after 2 years in service it shows the beginning of decline. So a coolant drain and fill I recommend 3-4 years or 50k miles . Sooner is better on all the system and cooling system parts and block and head protection.

Spark plugs decline very fast contrary to bad information on the internet. Spark plugs should be replaced at least every 15 k miles or sooner depending on how the engine is used.



You asked I responded based on practical servicing of 100 plus vehicles min. Every year. Supported by analysis of engine, transmission and coolant .

When your vehicle warranty has expired completely then not doing easy to do and inexpensive servicing may cost you more by not.


Doing any service of this type and miles will NOT void any part of the remaining warranty.

Just because claims of longevity of parts while may be accurate to say never means they are giving the best performance and generally the systems used will show a reduced rate of performance. Even though so many say “my engine runs great no problems”!

ASE

 

Let me put it a way I know you will understand what In am saying Jeff. I an hit a 2 inch pattern @ 300 yards with everything just cleaned and oiled. But after about 20 shots the tight 2 inch pattern starts to widen. Now the servicing states clean and oil should be done every 250 rounds . So which is better for performance sooner or by the book.

 

I generally change things ahead of the recommended intervals. I use fully-synthetic motor oil and change it and the filter every 4,000 to 5,000 miles. Ain't no way I am going to 10,000 - even if the synthetic oil can handle that. Changing the oil & filter on the CX-30 is very easy too.

15k seems way too early for the transmission service. A service writer at the one of the Mazda dealership recommended it at 50k miles. It's a "sealed" system and doesn't have a dipstick. It uses synthetic fluid too, probably a proprietary type that is specific to Mazda. ( My '04 Ford F-150 has an old-school dipstick where you can see the fluid level and condition. ) I was considering having it done after 40k, which is coming up fairly soon. Coolant? With the long-life stuff, 7 years is not unreasonable - but ten years seems way too long. I was planning on having it flushed out at five years (which will be around 50k miles or so).

I can likely to do a 'drain and fill' with the coolant - in my own driveway - but the transmission is a little more complicated. Some transmissions have a drain plug on them, while others do not - which necessitates removing the pan, putting in a new gasket and finding the port where the fluid is to be added. I'm kind of nervous about screwing that up.

Spark plugs? I know that they used to be easy to do back in the day, but newer vehicles are more complicated. Maybe that's best left to a shop - I might need to go on YouTube and check into it. I used to have a Sentra and the plugs were on these tube-looking things that went down into the cylinder head. That was a long time ago, but I remember how odd they looked. I am surprised that the Mazda doesn't have the iridium or platinum plugs that are good for much longer. ( For what it is worth, our car has the NON-TURBO 2.5L Skyactiv engine. )

Thanks for the reply!!

 

Well I tried.

Let me try to put it a way I can see from your response you will understand?

First almost EVERY automatic transmission problem we get in the shop and my good freind that owns Transmission service shop for over 50 is caused from lack of or no general serving. General servicing is a simple oil pan and filter service.

Ok moving on from that small lecture ^^^


Common sense most of us have regarding new engines. I say most but more those born prior to lets say the 1990's. We do a couple things regarding them. One is a careful consideration to breaking them in.
And changing the oil and filter at or before the old school 500-mile break in period. Some of you all even used nondetergent oil. And it had merits pre 70's engines/. But I won't go into that.

So a brand new engine with all brand new and newly machined parts all rubbing together and sheading small bits of materiel during the break in period. This happens even on an engine manufactured this week of January 2025.
The first oil change when analyzed will show this material alone with other chemicals that were used during the assembly of the engines. EVERY Gasoline ENGINE has these contaminates. Most are drain out in the first couple of oil and filter service at 7k miles and then again at 15k miles. The oil filter used if compared to the transmission filter is superior. that's important to keep in mind for my next "lecture" portion of this response lol.

Automatic transmission.
Old school thought was dating back into the 90's,80s, 70's all the way back to 40's was that the automatic transmission seldom needed oil change service. ALL automatic transmission wear as they acquire miles and shed material as some contact parts constantly wear out under normal operation. Like the clutch-pack and friction materialled parts. Those transmission filter do not do the best job of catching all that material. Fortunately the pan sump does not have windage that truns up what settles in the pan under most vehcle operation. But nevertheless it accumulates and some of that accumulation is metalic. See where this is going? So is that material that is metalic from normal wear is picked up from the pan it will circulate through the complete transmission and all the sensitive operation parts like the valve bode and solenoid and pumps. Liquid sand paper LOL

The good news from what I hope I am scaring the BEJESUS" out of you is that will a regular servicing as I outlined your fluid will have a more cleaning operating environment and will actually go way past the warranty or estimate miles 100K Not thinking about what I posted you are more likely be in the growing percentage of owners having something go wrong with your transmission at some point in its like.


This is what I removed when I did my first transmission pan oil and filter service. I also had the oil analyzed (see my thread ).
At this point with my frequent oil and or oil and filter service my last oil sample only showed the oil and even recommend increasing my miles of oil service. But oil is cheap, and I will stick to my own personal oil service/ LOL







As for the spark plug again if you get off the internet for most information and talked to shops that do use an oscilloscope for diagnosis many aspects of issues on vehicles you would hard pressed to find any of them that would not suggest changing the plugs earlier then what is claimed by the spark plug manufactures and the auto manufacture will improve the engines performance which translates into lower emissions and better MPG.
Here is something that most don't know... As I owned 3 different Dynometers when I did DYNO runs for customers on a chassis DYNO I always suggested that on the day of their appointment to come early and change the spark plugs.
I have done over 1200+ Chassis Dyno runs over the years.

 

Mazda3 Things I like to do - Page 19 - Mazda Forum - Mazda Enthusiast Forums

























The water mentioned was some droplets left when I rinsed the long spout funnel to refill the transmission. WOW caught me off guard, but it shows how good the oil analysis was.

 

I have heard very good things about Blackstone Labs - at least pertaining to motor oil analysis. I have never used them myself, though.

Regarding the transmission oil in a 2021 CX-30, does it have an actual drain plug (like the engine crankcase) or does it require putting the car up on a hoist, removing several bolts, scraping off the gasket and dropping the entire pan? That's still the easy part. How do you fill the transmission fluid? I don't see a dipstick to ensure that it has the correct amount. On a similar note, I know that some shops will do a 'drain and fill' for the transmission.............while others do a "flush" with it. I also don't know if the CX-30 transmission even has a filter. I probably need to research this further.

Spark plug replacement SOUNDS simple, but I have never attempted it on this CX-30. Obviously, removal of the beauty plate is necessary - but that's pretty easy. Sometimes getting down to removing them can be difficult because of the design of cylinder heads, etc. I think I still have an old 'gapper' gauge! The last two vehicles where I actually replaced spark plugs myself were both Ford 302 V8 engines. One was an Econoline van and the other was a Mustang.

As I said before, flushing and filling the coolant is not that big a deal - provided I can get to the petcock valve on the bottom of the radiator. With the last vehicle I had where I changed the coolant (my old Sentra), it wasn't too bad at all. I just drained it all out, refilled it with water, ran the engine for several minutes, drained it out again - then refilled it with a 50/50 anti-freeze/water mixture.

That was a lot of metal that you got out of your transmission! I suppose that you drive it pretty hard.

 

That is a normal amount found in most transmissions ! It is more when a basic service goes over 50k miles or more .

No I don’t drive my Mazda hard. I have been to Sacramento Raceway 4 times , when the engine was completely stock and after the mods for times slips in the quarter mile .

I have been to Laguna Seca 2 times for fun .

that’s it other wise it is the Dailey driver and grocery hauler.

 

I just had a safety inspection done on our 2021 CX-30 and it passed. I knew it would, as it was inspected in Germany back in September before we shipped it home. I had to get that done before getting our new license plates from the Virginia DMV tomorrow. We have the "European" tags on it now - which expire next month. We are coming up on 40,000 miles and the car has been very good to us so far. By looking at the owner's manual and reading some things on-line, I figure it is soon time to take care of some maintenance items.

The owner's guide says the coolant is supposed to be done every ten years or 120,000 miles. No way am I waiting that long. I had it tested when the car was inspected last week and the Ph numbers were a bit off kilter from normal. That's on the list for upcoming work. I could probably do that myself in my driveway if I could find out where that little petcock valve is. Do I need to remove the 'skid plate' on the bottom of the car in order to access it? I cannot see very well by looking down from the top. It's certainly not as easy as it was on my old Nissan Sentra. Meineke said they could do a coolant flush for $200 - which sounded very, very high to me.

Second in line is the transmission fluid. It's a sealed system - but, from what I understand, it is best to NOT get a flush. Dropping the pan, changing out the fluid and replacing the filter (if it has one) is likely the way to go. I have no idea what a shop would charge for that service.

Third on the list is a brake fluid flush. It probably is not crucial, but the car is four years old now - so better safe than sorry. I think it uses DOT 3. Brake fluid is cheap, but the labor probably isn't. I never bled brakes myself, but helped a friend do it on his car.

Fourth is the replacement of the spark plugs. The owner's manual says 40,000 miles for turbo engine and 75,000 miles for the non-turbo engine. Ours is the non-turbo 2.5L. As per your recommendation, I'm probably best off getting that done along with the transmission service. What's bizarre as there's nothing in the owner's guide that mentions transmission fluid changes OR the mileage interval for the rear differential, the transfer case, etc.

I don't normally prefer dealership service departments, but I do have some concerns about a shop using the exact OEM transmission and the correct spark plugs. We intend to keep this car a long time and only have 9 or 10 more payments on it. As far as I am aware, the dealership will give me a loaner car for the day if I have them do enough work on the car. ( If not, then I'll take my laptop, pack a lunch and sit in their waiting room for a few hours. LOL! )

Any idea what the cost would be if I had ALL of this stuff done at a Mazda dealership?
1. Complete coolant flush.

2. Drain and fill automatic transmission fluid + replace filter if applicable (not a flush).

3. Bleed brakes and replace the brake fluid.

4. Replace all four spark plugs (2.5L non-turbo SkyActiv engine).

I will have changed the engine oil & filter already + am capable of replacing the engine air filter and the in-cabin air filter. That stuff is easy.

Thanks for your input!

 

1. There is a difference between a coolant flush and simply draining and refilling the cooling system.
2. The transmission service should IMO based on experience and empirical data every 40k miles max .
3. On all brake systems with ABS it really is better to have a service shop do the brake complete brake fluid replacement.
4.IMO and based on experience and data there are no spark plugs that can give their claimed performance more then 30k miles. As well if the the engine has more then 50k miles the coil spark plug boots should be replaced.

The information in the owners manual for all services are only recommended times and miles. Driving conditions and environment has a huge factor into the actual service time intervals which in most all cases is shorter.

Because labor rates vary from each state and in some cases which part of the state you live anyone giving estimates of labor cost w old need to at least live in the same state . Best advise is to shop around for estimates. Keep in mind you pay for better quality and experience which also means less chance of problems from having any service done .

Either a Mazda dealer or a shop that is ASE rated are the best service shops for both getting estimates and quality work.

last and it is more a lol I got, you Mazda does not have a Skid Plate, only a plastic under carriage cover.