Crankcase Contaminants (i.e. fuel and moisture) - any harmful effects during Extended OCI?

[The Critic]

Hypothetical situation.

Let's say a hybrid vehicle sees a lot of short trips and this causes an elevated quantity of fuel and moisture to be present in the engine oil.

The levels of fuel dilution and moisture remain acceptable but will obviously rise as the OCI progresses.

This particular vehicle only accumulates 5,000 - 6,000 miles per year.

The oil being used has an unusually high starting TBN; let's just say >10. It is expected that the fuel dilution and moisture levels will remain below dangerous levels, even after a 10K (2-yr) interval.

However, what are the negative consequences of allowing an oil with high(er) levels of fuel and moisture to remain in the crankcase for an extended duration of time? Even with adequate TBN reserve, what is the potential for damage to seals/gaskets? In this situation, should TAN also be monitored?

 

[JavierH19]

They are acidic and do harm the tbn and tan. The fuel will also chemically shear oils with a higher vii as the polymers can't handle it. As for damage to seals they really shouldn't get damaged with average dilution. They're not the exact same as the seals used in the fuel system. If it's not cold I'd likely use a cheap syn blend 10w-30 or 5w-20 and change 2-3x a year.

 

[DirectRejection]

Hypothetical situation.

Let's say a hybrid vehicle sees a lot of short trips and this causes an elevated quantity of fuel and moisture to be present in the engine oil.

The levels of fuel dilution and moisture remain acceptable but will obviously rise as the OCI progresses.

This particular vehicle only accumulates 5,000 - 6,000 miles per year.

The oil being used has an unusually high starting TBN; let's just say >10. It is expected that the fuel dilution and moisture levels will remain below dangerous levels, even after a 10K (2-yr) interval.

However, what are the negative consequences of allowing an oil with high(er) levels of fuel and moisture to remain in the crankcase for an extended duration of time? Even with adequate TBN reserve, what is the potential for damage to seals/gaskets? In this situation, should TAN also be monitored?

Corrosive wear.
I would have a rule of at least 1 year OCI regardless of miles.

 

[Triple_Se7en]

Hypothetical situation.

Let's say a hybrid vehicle sees a lot of short trips and this causes an elevated quantity of fuel and moisture to be present in the engine oil.

The levels of fuel dilution and moisture remain acceptable but will obviously rise as the OCI progresses.

This particular vehicle only accumulates 5,000 - 6,000 miles per year.

If I were the owner with driving habits like that in a non-Toyota hybrid, I would stay on battery-power.

 

[The Critic]

Corrosive wear.
I would have a rule of at least 1 year OCI regardless of miles.

Can you walk me thru the concept of Corrosive Wear? I always thought corrosion occurs when you have a surface that is unprotected by a lubricant, but it sounds like lubricated parts can still suffer this issue under certain circumstances.

 

[Zee09]

If I were the owner with driving habits like that in a non-Toyota hybrid, I would stay on battery-power.

I used to stop at several places in my neighborhood checking out properties in a 2016 CMax.
It started in electric mode and once you get the hang of it I was able to do the trip all on electric. Of course the winter would rule that out.

They had moisture issues on the earlier ones but they put a louver in the grill and I never got the white sludge under the oil fill cap like earlier versions did.

 

[DirectRejection]

Can you walk me thru the concept of Corrosive Wear? I always thought corrosion occurs when you have a surface that is unprotected by a lubricant, but it sounds like lubricated parts can still suffer this issue under certain circumstances.

The anti-corrosive components in the oil would become diluted or depleted with fuel dilution.

I wonder the outcome with E0.

Corrosive wear is often overlooked, but can become an issue over time.

Further comment is reserved for BITOG experts.

 

[ziggy]

When I got my license,I was 16 just turning 17 within a week. My dad used our local Mobil gas station. This was 1992. He had just bought a used 1991 Saturn sedan.hsd like 34,000 miles on it.test car. So for oil changes he had synthetic Mobil 1 put in and the owner,mark, us d only OEM filters he was cautious of being liable if things broke didn't work. So every 6 months my dad had him change the oil. And filter. Cheap assurance the word he used often. I cannot say how much mileage actually went on in the 6 months, but it was for sure under 3000 miles.it was prob more like 1,700. Overkill? Probably because back then Mobil one was the real stuff.
My 98 LeSabre handbook says change oil every 3 months or 3000 miles whichever comes first. The reason I've learned car books say x amount of months is because acids carbon build up,and sheer oil, corrosive damage. It's best too do the 3 miles in 4 months. The idea is too Italian and tune up the car ,drive it 20 miles once a week at 60-75 mph. Nonstop .it's the stop n go that causes acids n carbon too build up they don't run long n hit enough too burn out the tailpipe. Hence 3 months oil change window.

 

[Nuclear_42]

Amsoil just recently released a hybrid vehicle motor oil addressing your same concerns. Now probably any name brand synthetic with your oem recommendations is fine but if your looking for something a little extra it's a solid choice.

https://amsoilcontent.com/ams/lit/databulletins/he_g3830.pdf

 

[oil pan 4]

I have the same problem with my wife's car it's a direct injection hybrid gets ran about 8,000 a year. The winter oil gets about 3,000 miles due to fuel dilution.

 

[KrisZ]

I wouldn’t worry much about fuel contamination as it blends fully with the oil. Too much of it depletes TAN and TBN and can cause acidic corrosion. I think that’s what @Direct_Rejection meant. Traditional corrosion, which is oxidation, will not be present on oil coated parts.

However, moisture doesn’t blend with oil, only mixes with it when agitated by normal operation. So when the vehicle sits for prolong periods of time, it can separate and cause corrosion. That would be my concern with moisture.

 

[The Critic]

Bumping this up - are there any published studies on corrosive wear?

Also curious if there have been any studies on the impact of crankcase contaminants on seals/gaskets. Does having sufficient TBN remaining always result in effective neutralization of acids?

 

[oil pan 4]

Bumping this up - are there any published studies on corrosive wear?

Also curious if there have been any studies on the impact of crankcase contaminants on seals/gaskets. Does having sufficient TBN remaining always result in effective neutralization of acids?

Well I know first hand what weak acids do to most seal materials.
One of the addtives that makes for a good tbn number is KHO. If there's any KHO in the oil it's not going to be acidic.

 

[zray1]

Can you walk me thru the concept of Corrosive Wear? I always thought corrosion occurs when you have a surface that is unprotected by a lubricant, but it sounds like lubricated parts can still suffer this issue under certain circumstances.

Cars with a high amount of blow-by, like classics, can definitely make the oil corrosive. To the point of damaging the plain bearings found on the crankshaft and connecting rods.

This is why classic car owners are counseled to change the oil before letting the car sit over the winter season instead of waiting for the spring driving season to do so. Leaving the bearings to sit in the “acid bath” for several months can and has etched the bearings. Depending on the severity of the oil contamination of course.

 

[buster]

One of the issues is moisture and emulsification. ASTM-D7563. It's been stated the oils with more polar base oils help dissolve a lot of these contaminants. I would think that benefits seals.

 

[buster]

"I'd just worry about TAN to be honest. I've always found it wild that if you're using a .5% ash oil you would condemn the oil at a TBN ~2.5. And yet if you switch the same engine over to a 1% ash oil, all of a sudden you need to trash the oil at a TBN of ~5. Makes no sense."

I think TAN is important. I can't imagine acidic oil is good for engine seals.

Corrosion inhibitors will kick in but there is not standard test to measure them and how effective they are.