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Old 08-07-2019, 07:13 PM   #30
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Default Re: Oil. Is this the real deal or ?? Major bullet points and concerns

Originally Posted by 4wheeldog View Post
Just as a data point, I had an analysis done on the original
oil in my Sprinter at about 8k miles. There was barely a trace of fuel present.
Very good to know. Did you idle a lot or do a lot of city driving (stop-go/short trips)?

Originally Posted by 4wheeldog View Post
I am careful to avoid high levels of biofuel, which is the more likely issue with contamination.
Now that's something we can all agree on. Even 0% when possible.

Originally Posted by 4wheeldog View Post
Thicker oil does not seal rings better than the appropriate oil. And the issue with fuel contamination of lubricating oil is not just loss of viscosity.
I may have worded that poorly, but everything I found points to this: starting out with a thin oil, then diluting it with fuel due to a LOT of idling or short trips, is going to result in a lower viscosity oil, which results in damage to the piston (and other parts), which results in even more accretion, versus starting out with a thicker oil. But you can't just use thicker oil year-round, there's a critical temperature component. Here's what I found doing some research:
The biggest issue that arises from fuel dilution is the lowering of the oil’s viscosity, as fuel has a much lower viscosity than the oil (as well as possessing a lower vapor pressure and thinning effect), which in turn can cause the oil-fuel mixture to adopt a viscosity lower than it is designed for. This causes the oil to possess less-effective lubricating properties and causes the strength of the oil film to be reduced, which increases the amount of wear on the cylinder liner and the bearings—this arises from the fact that the oil film is crucial for reducing the friction between moving components by providing a barrier, and the thinning of the oil causes the effectiveness of the barrier to be reduced, thus increasing the amount of wear on the system.
What happens if the viscosity becomes too low? This causes contact between the metal surfaces, leading to rapid wear of the bearings due to friction. Once this anomaly happens, there are number of effects. One of these is the washing of the liner walls, the piston skirt and the segments, which implies that the fuel wipes away the oil, leaving the area without lubrication and the liner walls polished. Although this may sound like everything has been given a great clean, nothing could be further from the truth: in reality, the lack of lubricant means that the surfaces rub against each other, which causes wear. When polished, it is more difficult for the liner to keep the lubricant in the area, which can lead to faults such as the seizing up of the piston and of the liner itself.

Another effect of fuel leaking into the crankcase is oil dilution. This causes the lubricant to lose viscosity, meaning that the films formed are weaker and less capable of withstanding high loads that can occur at certain points, such as the rod bearings and crankshaft areas.

As for light-duty vehicles, several cases have been observed in which the oil level increased instead of decreasing, resulting in several instances where the level far exceeded the maximum mark on the dipstick. Although this may seem like good news, it is not: in such instances, not only does the same dilution problem occur, but it is also particularly serious, given that in such cases the concentration of fuel is very high and can cause rapid wear and engine failure. Occasionally you may detect a drop in pressure and/or power if this is the case.

Some manufacturers have actually added a new notch above the maximum mark as a warning sign. If you notice an increase in the excess level, you should reduce the mileage interval for changing the lubricant by half. This instruction is included in the maintenance manual of the vehicle and must be observed in order to maintain the warranty.

Furthermore, as the lubricant is being used up (1 liter per 10,000 kilometers) and replaced by fuel, the concentration of additives decreases, meaning that part of their protective action of the engine is lost.

In the specific case of diesel cars, diesel fuel also enters the crankcase as a result of post-injection during regeneration so that the fuel gases can reach the crankcase and help the regeneration process by providing heat. As not all diesel fuel turns to gas, part of the fuel enters the crankcase, which produces the dreaded oil dilution.
When comparing oils, it is important to take into account the location in which the car will be used. Thin oils that are less prone to thickening in low temperatures will help you start your engine more quickly in winter while thick oils that are less prone to thinning in hot temperatures will help your engine perform better in summer. As a result, 0W-20 and 5W-30 oils have been developed for colder climates while 15W-40 and 20W-50 oils have been developed with hotter climates in mind.

Back to me writing. While the above topic is still uncertain to me, but it is gaining clarity, and I'm now putting a 60-70% conviction rate on this conclusion: If you idle a lot, city/stop-go/short-trip a lot, you should use thicker oil in the summer and winter, in accordance with MB's recommended chart (see attached), and as appropriate for your climate.

I am now 100% certain that idling or city driving/short trips cause a much larger amount of fuel accretion. MB tells us that in the manual. It's settled.

I'm also 100% certain that MB service centers use 0W 30, which is an all-year oil, with somewhat low viscosity (30), but also good for very cold temperatures (hence 0W means).

I'm also 100% certain you do not have to use Mobil 1 0W 30 oil to maintain your warranty. It's right there in the manual. (* See below for update on this next line): You can use 20W 50 and still safely operate the vehicle down to 23F, or you can use 10W 60 and safely operate the vehicle down to 5F. I've attached the relevant section from page 330 of the 2019 Owners Manual where it states this clearly and provides a chart.

UPDATE! It must be 229.52 spec, and there does not currently appear to be a 10W 60 or 20W 50 oil that is MB-approved 229.52 spec. They should remove the chart on that page of the manual. It's misleading if you want to stay within warranty. Whether it's still beneficial for prolonged idling operation is another question, so if you do use those grades, don't go announcing it to MB.

Originally Posted by 4wheeldog View Post
I will continue to change oil at about half of MB’s recommendations
For most users, that's definitely wise. I plan to go further and adjust according to my usage patterns. Lots of idling and city driving, maybe 75% of the time, I'll change as often as 5000 miles. A month of heavy idling and very few short distance trips, I might go down to 3000. A good 50/50 mix of all driving types, maybe back up to 7500 or even 10K.

Originally Posted by 4wheeldog View Post
I will continue to use only the recommended lubricant.
That's also wise. No risk that you forget to change to a thinner oil in the winter, or get stuck in a surprise winter storm and have to crank using a thick oil, causing damage.

But it may not be ideal if you plan to idle all the time, or if you spend a year doing mostly short trips and city driving. In those conditions, if you make sure to use the appropriate weight oil per MB's chart (see attached), you may see a benefit from using a thicker oil. Again, its' still not settled for me, but I'm now leaning heavily toward this.

Either way, good luck!


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Last edited by mgladden2; 08-08-2019 at 04:59 PM.
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