Oil Temp Needed To Keep Oil Clean/Free of Moisture and Fuel ?

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Hi all, I guess this is a follow up post to my other thread about oil temperatures. As I have a Subaru DIT engine in my WRX, I'd like to know what oil temp is needed to help reduce fuel , moisture, and contaminants in motor oil

I know engines with short driving cycles can have higher levels of fuel dilution, moisture and contaminants in the oil if oil temps don't get high enough. My last car was a Honda Civic 1.5 L motor driven in winter conditions and it had poor fuel dilution issues, I could never monitor oi temps on that car. My WRX has an oil temp guage so it can be easily monitored. I tend to get oil temps around 80-90 degrees C right now on most driving cycles, that would be on a distance of 10 miles or more. Is 80-90 degrees C enough to keep oil as clean as possible on a DIT engine ?

Thanks for any replies on this.
 
I think it's a "temp x time" equation. Obviously, if the oil is running at 80-90 C vs 100+ C then it's going to take longer to drive off fuel and moisture under the 80-90 C conditions.
 
Originally Posted by ZeeOSix
I think it's a "temp x time" equation. Obviously, if the oil is running at 80-90 C vs 100+ C then it's going to take longer to drive off fuel and moisture under the 80-90 C conditions.


Thanks for the reply, sure I guess the distance /time plays a factor as well as temp. In the past I heard people say don't take a car out of winter storage for short trips unless you drive it for 20+ miles with a fully warm engine.

But is 80-90 celsius degrees oil temp high enough to burn off fuel and moisture or is that still too cool ?
 
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I have some 2 year oci's with almost all city driving short trips, no fuel dilution or water in oil in uoa's. Other factors contribute to this other then just getting to 212 for extended times.
 
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90C will evaporate the water out relatively quickly. Some parts of the gasoline will evaporate out as well, but there are heavier components of gasoline with high boiling points and 80-90C is not enough to evaporate all fuel contamination. That's why all the bitogers that have GDI engines don't run more than 5k OCI
 
Originally Posted by burla
I have some 2 year oci's with almost all city driving short trips, no fuel dilution or water in oil in uoa's. Other factors contribute to this other then just getting to 212 for extended times.


Thanks for sharing that first hand information.
 
Originally Posted by JAG
Cool graphs, oil film movies.


I agree , very cool graphs oil film movies, that makes it very easy to understand. Thanks OFM
 
Originally Posted by SilverFusion2010
90C will evaporate the water out relatively quickly. Some parts of the gasoline will evaporate out as well, but there are heavier components of gasoline with high boiling points and 80-90C is not enough to evaporate all fuel contamination. That's why all the bitogers that have GDI engines don't run more than 5k OCI


Thanks for that information, it gives me something to think about. My car calls for 10,000 km oil changes on 5w30 (6300 miles approx.) Perhaps I should consider 5k miles (8000 kms ) ?
 
Originally Posted by JS2000

Thanks for that information, it gives me something to think about. My car calls for 10,000 km oil changes on 5w30 (6300 miles approx.) Perhaps I should consider 5k miles (8000 kms ) ?


How about both? I would suggest doing 8000 km intervals in the colder months and 10,000 km intervals when it's warmer out.
 
Originally Posted by oil_film_movies
[Linked Image]

[Linked Image]



I like figure 1.4

question about figure 2:
optimum temp range (the very bottom right of the graph) can be as high as 140°C (284°F) and yet it correlates to longest oil change distance? I would have thought 284°F would be way too high for any reasonable long distances let alone the max!

Edit:
maybe that figure is focusing on the oil life independent of the engine life. ie oil can handle that temp but engine (e.g. Seals, etc.) may not by going the max distance (16000 km).
 
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