2019 GTR 2.5T Oil Dilution

That’s unfortunate but it’s expected. I guess you can keep doing the UOA monitoring the oil dilution condition like Silly Wabbit suggested, in the mean time try a different oil. I’d try newer SP / GF-6 oil next time such as Idemitsu SP/GF-6 5W-30 oil. And here is ILSAC GF-6 performance relative to GF-5 and API SN Plus performance:

View attachment 297015

And Idemitsu SP/GF-6 5W-30 oil claims the following improvements over GF-6 standard although many say they’re exaggerating:
  • 30% more protection against engine wear
  • 26-46% reduction in oil consumption for longer life
  • Up to 24% improved fuel economy
  • 90% more resistant to viscosity increases
  • Three to four times more protection against cold startups
  • 91% reduction in low-speed pre-ignition (LSPI)
  • 6% cleaner engine
I think i'm going to switch to a euro spec oil. Per the manual it just needs to have a SN, SM or ILSAC approval rating. Like I mentioned the Castrol C3 oil is the leading candidate and it has a SN rating. Amsoil XL is also a little better than Amsoil signature and has ALL the ratings.

In case anyone looks at this with the same problem for the grade of oil specified (in this case 5W-30) you want an oil with a higher viscosity at 100 C and a high HT/HS value. This will resist dilution better. The Idemitsu GF-6 would actually be a downgrade from the Amsoil Signature as it has lower values for both of those.
 
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2018 CX-5 Sport
Edit: I did find this comment when googling: 'Most diesel engine oils carry a higher specification rating than petrol engine oils and vehicle manufacturers often specify a diesel engine oil be used in a petrol motor.'

Your car isn't a diesel right? Castrol C3 is for diesel engines, I don't know if that is the best for a gas powered car. Another option to check out would be 5w-30 full synthetic for high mileage cars. Change the oil at 3K on the new oil and see what the analysis shows, and you can determine how much longer you can go on the next new oil change.
 

yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
:
Plano, Texas, USA
I think i'm going to switch to a euro spec oil. Per the manual it just needs to have a SN, SM or ILSAC approval rating. Like I mentioned the Castrol C3 oil is the leading candidate and it has a SN rating. Amsoil XL is also a little better than Amsoil signature and has ALL the ratings.

In case anyone looks at this with the same problem for the grade of oil specified (in this case 5W-30) you want an oil with a higher viscosity at 100 C and a high HT/HS value. This will resist dilution better. The Idemitsu GF-6 would actually be a downgrade from the Amsoil Signature as it has lower values for both of those.
I have the same question like MyFirstMazda has, why would you choose an oil designed for diesel engine like Castrol EDGE 5W-30 C3 for your 2.5T?
Product Data
Description
Castrol EDGE 5W-30 C3, formerly SLX, engineered with fluid TITANIUM technology, provides superior motor oil strength for diesel engines that work harder due to higher engine pressures, helping your vehicle to maximize performance.

I have seen people using Shell Rotella® T6 Multi-Vehicle 5W-30 but at least it says for both diesel and gasoline engines.

For ACEA specifications used in Europe, ACEA A5/B5 specification usually is for gasoline engines; ACEA C3 specification seems to be always associated with diesel engines such as the Mazda SkyActiv-D 2.2L diesel.

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997928BF-A52D-4F10-AE54-EA1011361DB5.png
 
C3 can be used in either diesel or gasoline. It also carries the API SN designation which meets the requirements in the manual but I do see what you are both saying but it can be used in gasoline w/o mental gymnastics

"ACEA C3 Stable, stay-in-grade Engine Oil with Mid SAPS-Level, intended for use as catalyst compatible Oil at extended Drain Intervals in Vehicles with all Types of modern Aftertreatment Systems and High Performance Passenger Car & Light Duty Van Gasoline & DI Diesel Engines that are designed to be capable of using Oils with a minimum HTHS Viscosity of 3.5 mPa*s."

An alternative to C3 would actually be Amsoil XLF, which is an API SP (Resource Conserving), SN PLUS, SM, GM dexos1 Gen 2 (supersedes LL-A-025, 6094M and 4718M); ACEA A1/B1 A5/B5; Ford WSS-M2C946-A, WSS-M2C929-A, Chrysler MS-6395; Honda HTO-06; ILSAC GF-6A, GF-5, GF-4 compatible oil.

It's viscosity at 100 C is 11.1 cSt and a HT/HS of 3.3 cSt, which honestly is kinda the middle of ground of the normal conventional oil and the C3 oils. I'm a little on the fence between the two now though the castrol is MUCH cheaper.
 
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19 Diesel CX-5
C3 can be used in either diesel or gasoline. It also carries the API SN designation which meets the requirements in the manual but I do see what you are both saying but it can be used in gasoline w/o mental gymnastics

"ACEA C3 Stable, stay-in-grade Engine Oil with Mid SAPS-Level, intended for use as catalyst compatible Oil at extended Drain Intervals in Vehicles with all Types of modern Aftertreatment Systems and High Performance Passenger Car & Light Duty Van Gasoline & DI Diesel Engines that are designed to be capable of using Oils with a minimum HTHS Viscosity of 3.5 mPa*s."

An alternative to C3 would actually be Amsoil XLF, which is an API SP (Resource Conserving), SN PLUS, SM, GM dexos1 Gen 2 (supersedes LL-A-025, 6094M and 4718M); ACEA A1/B1 A5/B5; Ford WSS-M2C946-A, WSS-M2C929-A, Chrysler MS-6395; Honda HTO-06; ILSAC GF-6A, GF-5, GF-4 compatible oil.

It's viscosity at 100 C is 11.1 cSt and a HT/HS of 3.3 cSt, which honestly is kinda the middle of ground of the normal conventional oil and the C3 oils. I'm a little on the fence between the two now though the castrol is MUCH cheaper.
@osrk Did you ever find out what was wrong? Having the same issue. 2016 CX-9
 

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