I believe Mazda claims the SkyActive-G engines are Miller Cycle engines. Since they can phase both intake and exhaust cams at this point, that may only be under certain operating conditions. Anyway, that allows some amount of intake air to 'back out' into the port a bit. maybe that has some beneficial effect?
Skyactiv Intake Valve Deposits - Photos
- Thread starter buster
- Start date
Originally Posted by DBMaster
Originally Posted by buster
Originally Posted by DBMaster
I don't think those deposits look that bad. The Skyactiv engines have significantly higher compression than average (13:1). Part of the way that is achieved is through the use of special rings. Mine has 116,000 miles on it and I have been using 0W-20 for the entire time. I was going 30,000 miles between oil changes when microGreen filters were still available. Now, I'm at 15,000 mile OCIs with Mobil 1 0W-20 EP. I have never had to add make-up oil. So, I'm either getting fuel in the oil that offsets oil loss or the 0W-20 isn't leaking any measurable amount of oil past the rings. My UOA after 30,000 miles didn't show significant fuel dilution.
DB, have you ever posted a UOA? That would be interesting to see.
I have, but I'm too lazy to search for it. It's out there on this site, though. It showed what I was looking for - that my 30,000 mile oil was still serviceable and had adequate TBN.
I actually couldn't find it because you can only search posts dating back a year or less. I had saved the pdf so here it is.
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/06/full-51748-45956-capture.jpg "[Linked Image]")
Originally Posted by buster
Originally Posted by DBMaster
I don't think those deposits look that bad. The Skyactiv engines have significantly higher compression than average (13:1). Part of the way that is achieved is through the use of special rings. Mine has 116,000 miles on it and I have been using 0W-20 for the entire time. I was going 30,000 miles between oil changes when microGreen filters were still available. Now, I'm at 15,000 mile OCIs with Mobil 1 0W-20 EP. I have never had to add make-up oil. So, I'm either getting fuel in the oil that offsets oil loss or the 0W-20 isn't leaking any measurable amount of oil past the rings. My UOA after 30,000 miles didn't show significant fuel dilution.
DB, have you ever posted a UOA? That would be interesting to see.
I have, but I'm too lazy to search for it. It's out there on this site, though. It showed what I was looking for - that my 30,000 mile oil was still serviceable and had adequate TBN.
I actually couldn't find it because you can only search posts dating back a year or less. I had saved the pdf so here it is.
Originally Posted by wemay
Unfortunately, catch-cans don't stop the development of these deposits. There are countless examples of this shared on the various chat boards and even a recent "humblemechanic" video.
I almost bought a catch can for our only DI engine but did a lot more research and decided against it for this car. Also after 80K miles, the pcv valve and the connecting hoses were super clean and I found no oil gunk and/or oil residue along the path.
I assume if oil mists or vapours were looping back, I should have found some residue or condensation but I'm not an expert. Maybe a little oil goes or burns through the rings and causing the deposits and it's not coming from the pcv and the intake path ... at least this could be the case with our car.
I do favor low Noack oils and very reasonable oci however. Maybe that helped the pcv side being clean.
Unfortunately, catch-cans don't stop the development of these deposits. There are countless examples of this shared on the various chat boards and even a recent "humblemechanic" video.
I almost bought a catch can for our only DI engine but did a lot more research and decided against it for this car. Also after 80K miles, the pcv valve and the connecting hoses were super clean and I found no oil gunk and/or oil residue along the path.
I assume if oil mists or vapours were looping back, I should have found some residue or condensation but I'm not an expert. Maybe a little oil goes or burns through the rings and causing the deposits and it's not coming from the pcv and the intake path ... at least this could be the case with our car.
I do favor low Noack oils and very reasonable oci however. Maybe that helped the pcv side being clean.
Man, that looks really good. I had over 100K miles on my 2.5L CX5 and no changes in economy or power (that I could tell). My current CX5 turbo has 42K miles on it. Doing fine, as well. The spark plugs just got changed and they looked excellent. My commute is similar to yours, and I use 5-30 Mobil 1 EP formula. OEM filters (Japanese).
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I can't recall if I already posted/shared this. This is from the Mazda 3 forum. I'd love to know if using Valvoline Modern Engine would have made a difference.
"so here we go...
PURPOSE: when mazda designed and started manufacturing the skyactiv-g engine that is in all of our 3rd gen cars, they decided to use direct injection. as we all know, no fuel hits the back of the valves with this design. many manufacturers have had problems with buildup of carbon on the intake valves causing loss of power and fuel economy. mazda was very clear that their design would allow the valves to run much hotter and prevent buildup of problematic carbon. the purpose of this is to try and determine if that is true or not. i think you'll find the results interesting.
ABOUT MY CAR:
- 2015 mazda 3, built in mexico
- i purchased new, original owner
- 2.0L skyactiv-g, manual transmission
- mileage at the time the images were taken is 130,470 km
HOW IT IS MAINTAINED:
i perform ALL of my own maintenance and have since day one. as per the owner's manual, oil changes are every 8000 km. this is the schedule specific to canada and i have adhered to it strictly in both distance driven and time. in fact, i tend to do my maintenance a little early since i do not want to go over. i use castrol edge 0W-20 and ONLY this oil. it is considered a synthetic oil. i also use the OEM oil filters from the dealer. the filter is changed at EVERY oil change.
in short, i take good care of my cars. why castrol? i can get it cheap and it's easy to get here. it is specifically recommended in the owner's manual.
all other regular maintenance items are kept up to date with just as much rigor. air filter, regular checks, etc.
injector cleaners, engine shampoos, seafoam and other such snake oil is NOT used. EVER! your fuel already has detergents in it, so i consider it unnecessary and potentially harmful. if your clothes come out of your washing machine clean, adding more soap isn't going to do any good...
HOW IT IS DRIVEN:
i generally drive 20km/h over the speed limit on highways and 10km/h over in the city. conditions permitting of course. i commute to work, my drive is 95 km (yes i googled it). drive time is about an hour. most of my use is highway, but i do some city driving where i live. there are a good deal of hills on my drive and the city i live in is built in a big valley. i tend to accelerate fairly hard, but i'm not completely insane on the road. we'll say 'spirited' as mazda puts it. normally, i'd say my engine doesn't see much beyond 4000 rpm too often. i use cruise control often.
this car is driven in ontario, canada. as such, it sees temperatures over 30ºC and under -30ºC. we see all extremes here. i use a block heater in the winter to help it out. winter time i have a set of winter tires which negatively impact fuel economy.
FUEL:
i usually fuel up at the Esso around the corner which is considered a 'top tier' fuel station. i put regular 87 octane in as the more expensive grades doesn't do a thing for this car.
MODIFICATIONS: none. completely stock. not even an oil catch can.
SYMPTOMS: none that i can detect. i suspect i've lost a little power and fuel economy since it was new, but nothing too significant. this is purely exploratory. my car does not burn oil - at all. typical fuel economy is roughly 600km per tank. works out to somewhere around 6-7 L/100km. do note that speed has a HUGE impact on the fuel economy in this car. if i drive slow (the limit) i can drop the fuel economy under 6L/100km easy. especially if it's an 80km/h highway. all the hills i drive have an effect. i try to coast in gear to take advantage of the deceleration fuel cutoff as much as reasonably possible. fuel economy isn't so great in the winter as expected.
in short, i am probably in the best position to look for carbon. regular boring joe driving with nothing that could potentially upset the results.
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/06/full-564-45786-cyl_1_port_1.jpg "[Linked Image]")
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/06/full-564-45787-cyl_1_port_2.jpg "[Linked Image]")
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2020/06/full-564-45788-cyl_3_port_2.jpg "[Linked Image]")
Use some CRC intake vale and turbo cleaner on those valves - -your skyactive will thank you.
I have a 2016 mazda 6 and do a CRC every 10-15k kms. My valves are spotless.
I ran a borescope down the intake mani a while ago to see if the CRC did anything....it does.
Pics?
My driving experience over 61 short years cars generally always get the very best mileage they are going to get right at about 1K miles of break in. But I'll check back in with you in another 60 and see if I've changed my mind.
I am close to 15000 miles and my latest fuel economy number is 33.6mpg which surprised me since it’s winter. I usually get around 30.
I'm not selling catch cans- but I did install one on my DI Honda, amazing the crap that goes through the PCV system.
manufacturers are "moot" about DI issues, some worse than others + turbod DI engines seem to be worse + as many trade often it matters less. those like myself go for the long haul, 200 thou on my traded port injected 2001 VW 1.8T with an enhanced 275 TQ + HP, a fun trouble free ride replaced by another lo mile 1.8T an Audi TT 225Q roadster about 300 enhanced TQ + HP, my fun retired present to myself. Redline lubes only as it has a 4.25 qt sump, small like the jetta which got Amsoil early on then Redline
Really enjoying my 2017 Yaris with the SkyactivG 1.5L Has a pretty funny looking cat fish front end, but a good car overall. Also funny is how every badge is Toyota, even the engine cover.
65 mph steady interstate gets me 48-50 and city driving 42.
Premium gas always though.
Watched a very good youtube video from a guy in Thailand I think, on pulling intake manifold and cleaning Skyactivs. Looks fairly easy to do compared to other cars.
65 mph steady interstate gets me 48-50 and city driving 42.
Premium gas always though.
Watched a very good youtube video from a guy in Thailand I think, on pulling intake manifold and cleaning Skyactivs. Looks fairly easy to do compared to other cars.
De-badge it! I hate all the badges and the stickers to ID what I know I drive. Look at my signature picture closely.
Removing the intake is not bad and straight forward, but the procedure to blast clean is a mess! If you do have excessive carbon it is worthwhile task!
