1.5l Skyactiv G Miata 2018 2.5% Fuel Dilution?

[Zdos123]

I've owned a 2018 ND Miata (with the 1.5 Skyactiv G) for about 4 months now, in that time i've covered just about 7k miles. I just recently got an oil change and as per usual i took an oil sample and sent it off to Millers Oil for analysis. upon receiving the report back i was advised to be aware and to take notice of the fuel dilution which sits at 2.5%.

So the question is, is that normal/acceptable, i previously had a 1.8 NC Miata with the MZR-L8 engine which used Multi-Port fuel injection, in all my oil samples of this car it reported 0.5% every time without fail with almost double the mileage on the engine and a 10k oil change instead of a 7k oil change on the ND. Both cars have been used identically with 2 1 hour drives every day of hard country road driving at around 40-60mph with frequent 200+ mile journeys, so there's no fuel dilution from short journeys.

I got in contact with the Mazda dealer i bought it from and they said in their experience that shouldn't cause engine issues (i was already talking to them about a rough idle) but i should contact Mazda UK for further advice as they didn't know the correct specifications.

I've attached the report from millers oil, would someone please advise, it's driving me nuts.

Thanks,

Zdos123

 

[fantastic]

Looks like a 5w-20? That percentage isn't the end but something to take into consideration. You can move up a grade to 5w-30 to give a slight buffer. You could then go out to your usual 10k interval if your samples look good.

 

[Zdos123]

Looks like a 5w-20? That percentage isn't the end but something to take into consideration. You can move up a grade to 5w-30 to give a slight buffer. You could then go out to your usual 10k interval if your samples look good.

I believe it's 0w-20 as mazda specifies for it, i already bumped it up to 5w30 when i took this sample (still acceptable in mazdas books).

I think my main question is more is this anything to be concerned about in terms of future issues, it's on 50k miles now and i plan to take it to about 150k over the next 4 years and am wondering if there's any sort of underlying potential fault or if it's just in the engines nature, it does run quite rough at idle but mazda has told me "they all do that".

 

[LeoStrop]

Does it have an oil temperature gauge? Based on your driving style, it surely doesn't look like fuel dilution should be happening.

You could ask to re run the sample, maybe it's an error.

 

[fantastic]

I believe it's 0w-20 as mazda specifies for it, i already bumped it up to 5w30 when i took this sample (still acceptable in mazdas books).

I think my main question is more is this anything to be concerned about in terms of future issues, it's on 50k miles now and i plan to take it to about 150k over the next 4 years and am wondering if there's any sort of underlying potential fault or if it's just in the engines nature, it does run quite rough at idle but mazda has told me "they all do that".

If it's a Direct Injection design it's perfectly usual to see that percentage of fuel. You've already went up a grade but the reading on your sample is pretty low for a 30 grade. Other option would begoin to a 0w-40 or 5w-40. Is the car driven hard?

 

[Zdos123]

Does it have an oil temperature gauge? Based on your driving style, it surely doesn't look like fuel dilution should be happening.

You could ask to re run the sample, maybe it's an error.

Unfortunately no oil temp guage, just a useless coolant temp guage which displays the only useful bit of the guage in the far left hand corner and then the rest is left only for when the engine is violently overheating but from what i've experienced the coolant temp gets up to temp about 15 minutes into my drive on 30mph roads and behaves exactly as my last NC did.

I'm not sure about re-running the sample, but i will query it with the guy i spoke to about the sample at millers.

 

[Zdos123]

If it's a Direct Injection design it's perfectly usual to see that percentage of fuel. You've already went up a grade but the reading on your sample is pretty low for a 30 grade. Other option would begoin to a 0w-40 or 5w-40. Is the car driven hard?

Sorry i should have phrased it better, the oil sample is from Mazdas own 0w20, after this sample i changed the oil to Mobile 1 Super 3000 FE 5W30 which i've only done about 500 miles on.

The car is driven very hard, it sees redline multiple times a day and will eventually start taking part in autosolos (but not trackdays as they are a step to far for in a daily imo).

 

[fantastic]

Sorry i should have phrased it better, the oil sample is from Mazdas own 0w20, after this sample i changed the oil to Mobile 1 Super 3000 FE 5W30 which i've only done about 500 miles on.

The car is driven very hard, it sees redline multiple times a day and will eventually start taking part in autosolos (but not trackdays as they are a step to far for in a daily imo).

Ah, that makes sense. So the 30 grade should suit you after all. Results look good overall.

 

[OneLonelyBurrito]

I wouldn't worry about 2.5% fuel in the oil when everything else is in check and normal. That amount is pretty normal in direct injected engines like the Skyactiv-G engines.

 

[Zdos123]

I wouldn't worry about 2.5% fuel in the oil when everything else is in check and normal. That amount is pretty normal in direct injected engines like the Skyactiv-G engines.

Thanks, i guess it's cause my last MX5 was the MK3 with the MZR-L8-VE which was port injected and a comparitively an ancient lump with terrible mpg and crap engine noise no matter what exhaust you put on it but at least it was absolutely bomb proof haha

 

[Lilliston]

2.5% (assuming a GC number) is pretty typical for a SkyActive-G, maybe even slightly lower than average.