Exactly my thought, though I don't really know how it would tie in with the cold weather overfueling, unless something in the system is getting crossed signals.
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2.5L Oil level fluctuation
- Thread starter Sekmor
- Start date
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I did not use proper terms to describe the relationship between LSPI and the knock sensor. When the sensor detects the knock, it is too late to adjust anything, the uncontrolled blow-up is in the process at this time, no warning signs. As LSPI events are more powerful and destructive then "normal" detonation, OEMs proactively avoid the conditions that cause them, based on statistics gathered during their testing. The loop in that case might be closed, and the ratio would be just on the high side of stoichiometric, or slightly above. Not sure if opening of the throttle is involved at that time as well.
That's how I see it working.
Skyactiv engines have quite high compression rate, so the conditions during combustion are quite similar to regular turbo...
If the above is right, the oil doesn't matter much, as the ECU is programmed to dump fuel at LSPI- likely conditions, Moly or not. I guess, they tested with their high- Moly to get the statistical data, hence they recommend it.
That's how I see it working.
Skyactiv engines have quite high compression rate, so the conditions during combustion are quite similar to regular turbo...
If the above is right, the oil doesn't matter much, as the ECU is programmed to dump fuel at LSPI- likely conditions, Moly or not. I guess, they tested with their high- Moly to get the statistical data, hence they recommend it.
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- Plano, Texas, USA
I'm with you and either way oil with high moly content should be beneficial to SkyActiv-G engines by decerasing LSPI. I also remember someone had mentioned before our SkyActiv-G engines don't have knock sensor as they have other ways to handle engine knock?
They have a knock sensor
It's based on stochastic analyses
Since it's based on stochastic analyses, which is the prediction of a completely random event, which having done many of these is not a trivial task given the large number of variables, HIL (Human In the Loop), etc, we have no way of knowing what parameters, inputs, outputs, etc Mazda used to program their logic in the PCM to avoid LSPI.
We only can use empirical data, like garycar, myself & a few others have gathered and that ambient temperature, oil temperature and time at temperature are the key variables causing or preventing over fueling.
It's pretty cut and dry. If you make extended short mileage trips in low ambient temperatures, then you don't get to a high enough oil temp for a long enough period to vaporize the low boiling point fuel out of the engine oil. I have over 65,000 miles of documentation to prove it, along with garycar and others.
As far as the high compression being equivalent to a turbo engine, that is quite a stretch and inaccurate. Even at 13:1, that's a far cry from today's small displacement, high boost engines with effective compression ratios of 20:1 or more. Also, the skyactiv-g, has a theoretical mechanical compression ratio of 13:1 in NA, but over much of its operating range, the true compression ratio is far less, as it adopts the Atkinson cycle, where the expansion ratio is greater than the compression ratio, so an effective c.r. would be about 11:1, based on 90-91 RON or 87 MON.
Since it's based on stochastic analyses, which is the prediction of a completely random event, which having done many of these is not a trivial task given the large number of variables, HIL (Human In the Loop), etc, we have no way of knowing what parameters, inputs, outputs, etc Mazda used to program their logic in the PCM to avoid LSPI.
We only can use empirical data, like garycar, myself & a few others have gathered and that ambient temperature, oil temperature and time at temperature are the key variables causing or preventing over fueling.
It's pretty cut and dry. If you make extended short mileage trips in low ambient temperatures, then you don't get to a high enough oil temp for a long enough period to vaporize the low boiling point fuel out of the engine oil. I have over 65,000 miles of documentation to prove it, along with garycar and others.
As far as the high compression being equivalent to a turbo engine, that is quite a stretch and inaccurate. Even at 13:1, that's a far cry from today's small displacement, high boost engines with effective compression ratios of 20:1 or more. Also, the skyactiv-g, has a theoretical mechanical compression ratio of 13:1 in NA, but over much of its operating range, the true compression ratio is far less, as it adopts the Atkinson cycle, where the expansion ratio is greater than the compression ratio, so an effective c.r. would be about 11:1, based on 90-91 RON or 87 MON.
Re: my Mazda CX 5 gas engine oil being diluted with gas during the winter.
My dealership just informed me that the TSB mentioned earlier in this thread was already performed on mine. I believe it was in February 2015. I still have the issue though. I changed the oil and filter on December 31 (only filled the oil to halfway between add and full) I checked it last night and is already a little over the full mark on the dipstick. My wife drives 10 km to work and 10 km back home for lunch; then back to work and back home. The blue coolant engine light goes out halfway to work. I also have a cover on the front of the vehicle and still the oil is rising. I am wondering how full is too full and how diluted with gas is too much. My concern is that too much gas in my oil could cause engine damage. I usually change it when it reaches 1/2 - 5/8 of an inch over the full mark. Another Mazda dealership told me yesterday that because steam comes through the exhaust, there needs to be a good sized hole drilled in the muffler because in cold weather and short trips ice builds up in the muffler, and this causes the problem. And on it goes. Tonight I will take a hair dryer and crawl under the vehicle and heat up the muffler and see if any water comes out the small weeping hole that is already there. Maybe I need to drill a bigger hole. As i said earlier in this thread, I have no problems during the summer. Its only a winter problem.
My dealership just informed me that the TSB mentioned earlier in this thread was already performed on mine. I believe it was in February 2015. I still have the issue though. I changed the oil and filter on December 31 (only filled the oil to halfway between add and full) I checked it last night and is already a little over the full mark on the dipstick. My wife drives 10 km to work and 10 km back home for lunch; then back to work and back home. The blue coolant engine light goes out halfway to work. I also have a cover on the front of the vehicle and still the oil is rising. I am wondering how full is too full and how diluted with gas is too much. My concern is that too much gas in my oil could cause engine damage. I usually change it when it reaches 1/2 - 5/8 of an inch over the full mark. Another Mazda dealership told me yesterday that because steam comes through the exhaust, there needs to be a good sized hole drilled in the muffler because in cold weather and short trips ice builds up in the muffler, and this causes the problem. And on it goes. Tonight I will take a hair dryer and crawl under the vehicle and heat up the muffler and see if any water comes out the small weeping hole that is already there. Maybe I need to drill a bigger hole. As i said earlier in this thread, I have no problems during the summer. Its only a winter problem.
The Role of the Lubricant in LSPI
Many factors have been demonstrated to impact LSPI, including: engine designs, fuel composition, and lubricant composition. On the lubricant side, the most noticeable impact has been from the detergent chemistry. Oils with higher concentrations of calcium, which is found in many detergent systems, have been shown to increase the frequency of LSPI. The exact chemistry of the detergent is less important to LSPI than the calcium content. Conversely, magnesium-based detergents do not seem to promote LSPI. Although reducing calcium may seem like a solution to control LSPI, there may be other performance tradeoffs to consider. In addition there are other additives that can also help reduce LSPI events. This provides an opportunity to formulate for robust LSPI performance, while maintaining the level of detergency needed to help keep engines clean and neutralize acids generated during combustion.
Aside from the detergent system, there are many other additive and lubricant compositions that can influence LSPI. Molybdenum compounds, for example, not only provide frictional benefits, but also have been shown to decrease LSPI when used at high levels. Base oils also affect LSPI events. Both the quality of the base stock (i.e. Group II versus Group III) and the viscosity can have secondary effects on LSPI. The effect on LSPI from these other lubricant aspects are not as significant as the detergent system, but can shift the LSPI frequency in oils that are more prone to LSPI.
Many factors have been demonstrated to impact LSPI, including: engine designs, fuel composition, and lubricant composition. On the lubricant side, the most noticeable impact has been from the detergent chemistry. Oils with higher concentrations of calcium, which is found in many detergent systems, have been shown to increase the frequency of LSPI. The exact chemistry of the detergent is less important to LSPI than the calcium content. Conversely, magnesium-based detergents do not seem to promote LSPI. Although reducing calcium may seem like a solution to control LSPI, there may be other performance tradeoffs to consider. In addition there are other additives that can also help reduce LSPI events. This provides an opportunity to formulate for robust LSPI performance, while maintaining the level of detergency needed to help keep engines clean and neutralize acids generated during combustion.
Aside from the detergent system, there are many other additive and lubricant compositions that can influence LSPI. Molybdenum compounds, for example, not only provide frictional benefits, but also have been shown to decrease LSPI when used at high levels. Base oils also affect LSPI events. Both the quality of the base stock (i.e. Group II versus Group III) and the viscosity can have secondary effects on LSPI. The effect on LSPI from these other lubricant aspects are not as significant as the detergent system, but can shift the LSPI frequency in oils that are more prone to LSPI.
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- Plano, Texas, USA
Re: my Mazda CX 5 gas engine oil being diluted with gas during the winter
LSPI Chart: High or Low Calcium
Additive effects on the frequency of LSPI in the Ford test. The "High Ca" oil has a calcium concentration typical of those in the market today. The Low Ca has been reformulated to resist LSPI, and is representative of how many next generation oils will behave.
What kind of oil do you use? High calcium content oil promotes LSPI.
LSPI Chart: High or Low Calcium
Additive effects on the frequency of LSPI in the Ford test. The "High Ca" oil has a calcium concentration typical of those in the market today. The Low Ca has been reformulated to resist LSPI, and is representative of how many next generation oils will behave.
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- Plano, Texas, USA
Knock Sersor
Thanks to both of you for the correction and showing the diagram. (2thumbs)
There's no way that your engine has an opportunity to get fully warmed up in your weather within the driving distance of your wife's job. I suggest, and I really don't like to suggest this often, that maybe you let it warm up for 10 minutes before she drives off? Or maybe take an alternative longer route to her job? I know in my area I don't get the engine fully hot until I've driven a good 8 miles and the weather around here is at least a good 30 degrees "warmer" than where you are in winter, and you're driving less than that in colder weather. You have to find some way to burn off that fuel dilution. Getting it hot enough to burn off the excess is the only key I see here. I don't see any good outcome with highly diluted oil, not even discussing the sludge that will probably also build up in your engine because of constantly running cold.
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- 2016.5 CX-5 GT AWD titanium/black 2016 Miata Club ST MT white
I KNOW that you didn't use your wife's hair drier for this operation, right? (argh)
This oil dilution really has me concerned. The VW TDI that we just sold back to VW had a concern from oil dilution with the use of bio-diesel. VW even sent out a letter outlining the issue. Now I have to worry about our new Mazda as my wife only has a 5 mile trip to work. I'm retired so I've been driving her to and from work just so that the Mazda has a chance to warm up, and of course, so my wife has a chauffer in the cold weather.
Maybe add a block heater?
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- 2016.5 CX-5 GT AWD titanium/black 2016 Miata Club ST MT white
Good idea.
Mazda recommends 0W-20. So I have been staying with that. I use formula 1 synthetic oil from our Canadian Tire store. I am told it is the same as Quaker State, only in a different container. I looked on the container and there is no mention of how much calcium is in it. Do you know of a brand of oil that has low calcium. I am willing to try anything? Thanks
I actually decided to use my heat gun. Better choice. ha. I noticed two small holes had already been drilled in the muffler. I heated the muffler up good and hot and not a drop of water came out. So that theory is out the window. Last night I drove the vehicle on the highway 100 km in manual mode 5th gear to keep the rev up higher. I checked the engine oil this morning before start up and it dropped 1/4 of an inch. After my wife goes to work today, I will be back on the highway tonight to burn off the gas that was build up from today. I am wondering which is cheaper; burn more gas driving or change the oil every two weeks. Ah decisions
Block heater is an excellent idea. Short drives in cold weather is bad in so many other ways, fouls plugs, accumulation of unburned combustion byproducts in the engine (forms oil sludge, blocking oil passages, etc.), short life of the exhaust system, so I'd say burning more gas is cheaper in the long run. If it was a car out of the sixties I might have also recommended a hotter thermostat, can't do that these days.
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- 2016.5 CX-5 GT AWD titanium/black 2016 Miata Club ST MT white
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- Plano, Texas, USA
The problem for garycar is Mazda doesn't offer Mazda 0W-20 Moly oil in Canada. Calcium is used as a detergent for oil and the oil companies usually don't mention its content. People can only rely on UOA to tell which oil has high level of calcium. Molybdenum is added for better lubrication and it's expensive. Oil company will mention it because of that. From what I've known Red Line 0W-20 oil has high molybdenum content which claims the oil is equivalent to Mazda 0W-20 Moly oil p/n 0000-G5-0W20-MQ. Or you can even try Honda 0W-20 oil from Honda dealers which supposed to have high molybdenum content. I think it may worth a try to use different oil with high molybdenum content in winter and see if it could make any difference.
The most oil with most moly in it? 0w20 and 0/5w30
