Mazda 2.5L Turbo - Oil Fuel Dilution Issues?

Excessive Fuel oil dilution isn’t a known problem with this engine, but it is prone to some level of fuel oil dilution. Short commute in cold weather makes the fuel dilution worst. Because the engine doesn’t get warm enough to burn the portion of the fuel that can seap through the oil.

I know people don’t like this answer, but the real solution to prevent fuel dilution problem, is to conduct regular oil changes.

Unless your driving habit changes (if it remains used very little and on short commute) and that fuel oil dilution is a concern, i would recommend doing oil changes based on time interval (i.e. months since last oil change) as oppossed to mileage. The logic here being that changing the oil brings in new undiluted oil, and that driving little is actually worst for oil dilution than driving a lot.
 
... It was used very little due to work from home situation etc. ....
One thing to be aware of is that being parked unused for a number of days is not a problem for a vehicle (except possibly running the battery down too low). What is likely to become a big issue is lots of short trips, without having regular 1/2 hour+ drives mixed in.

So if your driving pattern is almost all short trips, then doing regular Italian tune-ups can greatly improve the long term health of your vehicle. Just find a time on a local high speed highway when traffic is light, and drive 25 minutes or so to completely warm your vehicle up. Then when no one is anywhere close behind you and it's a straight and safe section of road, drop your speed down to 20MPH or so, and then push the gas pedal hard to the floor and keep it there until you reach 75, or whatever is +9 over the speed limit for that highway. You probably won't smell much gas from the dipstick after doing that a few times on a single drive, and your vehicle's engine is likely to say thank you by remaining problem free.
 
Hi, this is my first post here. I have 2019 CX-9 Touring Premium 2.5T AWD that we purchased brand new and now has a little over 5000 miles. It was used very little due to work from home situation etc. I have an appointment this coming Saturday for the 5k service and I was doing a check on the vehicle to see if anything needs to be addressed by the dealer. I pulled the dipstick out and got a very strong smell of gasoline, cleaned it and tried again 3 times and still the same, oil level is well above the hot mark. Hopefully this is a fixable situation, I otherwise love the car.
There is a TSB(technical service bulletin) on this. Direct injection motors get oil dilution, it is the nature of the beast. The way to prevent this is to let the engine get to operating temperature before it is turned off, or driven hard. A oil catch can will help with this. Cork sport makes one that is a direct fit. My wife drives my cx-9 25 miles each way, and I have not noticed any oil dilution since she started driving farther away.
 
After reading the thread and seeing people trying to determine exact amounts and percentages.. I think things are a bit more complicated Some ideas to think about.

From what I understand gasoline is lighter than oil and would sit at the top of the oil in the pan. The drain is at the bottom. Depending on when you take the sample while pouring out you would not get the same reading of gas. Even pouring from a oil pan which collected it all would not give you exact reading unless you sent them the entire pan of oil to test. When you are pouring it into test container you will not be getting a perfect average of bottom/top fluids.

Gasoline also evaporates so determining how much has actually entered the oil system and not evaporated over time in a hot engine seems like a hard thing to determine.

Like if you had 5% gas in the oil when you did the test I would think that there is a good chance you had much more gas than that actually enter the oil system over the course of 6 months, some of it just evaporated and was burned via PCV perhaps?

I do not know of any oil results from any car that have not contained gasoline and even pouring the oil out and letting it sit in a pan for 30 minutes while the change is done could probably screw up tests as it could evaporate there in a warm climate etc.so would need to be straight for pan to container and really only give you result of how much was left in it at that exact moment etc. Drive from Toronto to Orlando non stop and drain and it would probably be a much different figure than a car the is occasionally run and has the oil drained cold etc. There are alot of variables.

Has anyone actually seen the slightest indicators of mechanical parts wearing prematurely in this engine?

My 1st engine in my Mazdaspeed protege was run pig rich for over 100k. I always used synthetic and the head and valvetrain still looked brand new when I took it apart so I can't imagine gas is that detremtal (though not desirable of course).

Just some thoughts to consider I'm not stating any facts just ideas here
 
Well I will state one fact. There is no chance in hell any of your 2.5T are running as rich as a Mazdaspeed Protege FSDET was from the factory and people who do not beat the s*** out of them have gotten 200,000+km out of a much cheaper and much more poorly designed engine. Sure it wasn't DISI but trust me there is more gas in their oil pans from cylinder washing at 10:1 AFR than a cx9 2.5t will ever see.

Perhaps there are bigger issues in life to worry about than a problem you will most likely never need to worry about in real life.
 
Hi there. Just tossing my two cent into this matter. Here is my cx 9 2016 Grand touring at 71k. Heads up I purchased car used and the owner might have not did an oil changed for 24k miles... When I purchased it, it did 2 flush (Liqui Moly 500ml Pro-Line Engine Flush) and cycle 3x fresh oil in 1k intervals to flush out any issue. That is why my first oil sample only had 1k on it. From what it seems my Viscosity is low with both sample. So it might be a normal thing with these. Blackstone didn't really made a big deal on it. First sample used. "Castrol GTX Ultra Clean 0W/20". 2nd one was " Super Tech Advanced Full Synthetic SAE 0W-20 Motor Oil rated for 20k miles.
 

Attachments

  • Screenshot_20220107-170611_Drive.jpg
    Screenshot_20220107-170611_Drive.jpg
    127.4 KB · Views: 139
Last edited:
Hi there. Just tossing my two cent into this matter. Here is my cx 9 2016 Grand touring at 71k. Heads up I purchased car used and the owner might have not did an oil changed for 24k miles... When I purchased it, it did 2 flush (Liqui Moly 500ml Pro-Line Engine Flush) and cycle 3x fresh oil in 1k intervals to flush out any issue. That is why my first oil sample only had 1k on it. From what it seems my Viscosity is low with both sample. So it might be a normal thing with these. Blackstone didn't really made a big deal on it. First sample used. "Castrol GTX Ultra Clean 0W/20". 2nd one was " Super Tech Advanced Full Synthetic SAE 0W-20 Motor Oil rated for 20k miles.

I'm guessing you meant 5W-30?

Anyway, nice report! Glad to hear your CX-9 hasn't given you any issues thus far.
 
Ya, 5-30w. Going to keep this suv as long as possible. Mazda is ending the cx 9 in USA market. They are switching to Cx-90 soon.
 
Just an update to this thread. I would often check my cx5 turbo oil level. I noted a fuel like odor. I kindof wrote this off as "whatever". I now check my rav4 prime oil level, and there is NO fuel like odor. It stood out to me because it is so different. That said...is this a problem? Due to lack of bearing and valve failures or fires, Id say not.
 
While I drive a CX-5, I am posting here woefully with the same engine and issue. Seems like this is the more active thread. Following along in hopes someone finds a solution.
 

Attachments

  • 19 CX5 GTR-230225.pdf
    173.8 KB · Views: 88

Latest posts

Back