Engine Oil sludge

[XxPuNTeRxX]

Hello,

My mirage now has 78000 kms. I have been doing my oil changes every 6months or 8000kms with any 5-20 from the auto parts store. Almost exclusively using a WIX filter. I've been noticing that the used oil has been forming a significant amount of thick waste. I'd say at least 100ml of the wasted oil turns quite thik. Rest of it is runny. Oil is also very gassy smelling. Is this normal for this engine ?

Thanks for the input

[Eggman]

I've been noticing that the used oil has been forming a significant amount of thick waste. I'd say at least 100ml of the wasted oil turns quite thik. Rest of it is runny. Oil is also very gassy smelling. Is this normal for this engine ?

No, that doesn't sound normal. Have your drained oil analyzed for problems and you'll get a better idea of what's going on with your engine.

One question though - do you make a lot of very short trips where your engine never reaches full operating temperature?

[XxPuNTeRxX]

No, that doesn't sound normal. Have your drained oil analyzed for problems and you'll get a better idea of what's going on with your engine.

One question though - do you make a lot of very short trips where your engine never reaches full operating temperature?

90% of trips were 16km distance stop/go trafic. I changed august to febuary so 75% winter condition. I mostly drive in low RPM 1200-1800.

[Eggman]

90% of trips were 16km distance stop/go trafic. I changed august to febuary so 75% winter condition. I mostly drive in low RPM 1200-1800.

It is my understanding that when an internal combustion engine starts, runs and warms up there is a certain amount of what's called blow-by that makes it's way from the combustion chambers, past the piston & rings, and into the crankcase. This includes unburned fuel as fuel injection systems deliver a rich mixture on cold starts. As the engine reaches it's full operating temperature, much of those volatile components will evaporate from the engine oil and be drawn in to the engine to be burned through the positive crankcase ventilation (PCV) system. Refer to the Wikipedia article Crankcase ventilation system for more details.

Some fuel is bound to find it's way into the crankcase. That's part of what the crankcase ventilation is supposed to take care of. That, and getting the engine up to temperature to help with evaporation. Lots of short trips during cold temperatures can contribute to a build-up of fuel in the crankcase. A malfunctioning crankcase ventilation system can also add to the problem, maybe more so if you are seeing sludge in your drain oil which could clog the crankcase ventilation system.

Our noses can detect some funny odors but it's not always clear what is unburned fuel and what is engine oil. And I can't smell it from here. A used oil analysis can give more info, or at least an expert mechanic's nose could help more.

[Top_Fuel]

A used oil analysis can give more info, or at least an expert mechanic's nose could help more.

Exactly.

If you suspect that you may have a problem, an inexpensive oil analysis will tell you exactly what is going on with your engine oil.

https://www.blackstone-labs.com/engine-types/gasoline/

[Loren]

Couple thoughts.

1. Is "any ol' 5w20" oil a synthetic or conventional oil? You live in Canada, and Mitsubishi specs 0w20 oil. I use that even in FL where it's warm... no reason to not use it in the frozen North. Oil weight is not a huge deal, I guess. Just costs you some efficiency and a very tiny bit of start-up wear. And for 5k miles @ 6 months, even conventional oil should be adequate.

2. You live where it gets cold, and I believe there's a recall to correct a cold-start over-fueling problem. If you've not had that done, you might look into it. Could account for the fuel smell, thinning of oil, and possibly some accelerated engine wear.

That's all I got.

[Eggman]

You live where it gets cold, and I believe there's a recall to correct a cold-start over-fueling problem. If you've not had that done, you might look into it.

Good point. XxPuNTeRxX has a 2014 model that if I recall is very much affected by this.