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Oil temp and MPG question

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Old Nov 11, 2013 | 02:47 PM
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Oil temp and MPG question

So, when Sport is engaged, my Oil temp drops from 225 degrees down to 200 degrees. MPG also decreases significantly.

Is the change in MPG just due to the extra parasitic drag on the engine from the oil cooler, or does the slightly hotter temperature of the oil also play into engine and fuel ignition efficiency?

Regardless, the efficiency of this engine is pretty amazing. I get 10-15 MPG when driving aggressively through the twisties, but I manage a very consistent 27 MPG when cruising on the highway. The former is to be expected from a sports car...the latter makes me a happy commuter when travelling for business and really makes the car a great daily driver.
 
Old Nov 11, 2013 | 03:43 PM
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Originally Posted by certified_prime
So, when Sport is engaged, my Oil temp drops from 225 degrees down to 200 degrees. MPG also decreases significantly.

Is the change in MPG just due to the extra parasitic drag on the engine from the oil cooler, or does the slightly hotter temperature of the oil also play into engine and fuel ignition efficiency?

Regardless, the efficiency of this engine is pretty amazing. I get 10-15 MPG when driving aggressively through the twisties, but I manage a very consistent 27 MPG when cruising on the highway. The former is to be expected from a sports car...the latter makes me a happy commuter when travelling for business and really makes the car a great daily driver.
I have have PDK, and the Sport setting sensitivity to revs means it shifts into lower gears more often. I suppose that means less mileage, but its good enough that I gave up caring some time ago.
 
Old Nov 11, 2013 | 05:54 PM
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I have a manual trans. And it's not just a more aggressive shifting point. I average a healthy 27 MPG in normal mode with highway driving consistently while in 6th gear. With Sport engaged, it is closer to 22-23 MPG I believe.

I am mostly just curious if that is all due to the parasitic drag from running the oil cooler. If so, no wonder why they went with electric steering to get rid of that pulley as well.
 
Old Nov 12, 2013 | 06:57 AM
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My tech would agree w/ you.
however thats a big decrease in your MPG. Strange.
 
Old Nov 12, 2013 | 07:15 AM
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Originally Posted by certified_prime
I have a manual trans. And it's not just a more aggressive shifting point. I average a healthy 27 MPG in normal mode with highway driving consistently while in 6th gear. With Sport engaged, it is closer to 22-23 MPG I believe.

I am mostly just curious if that is all due to the parasitic drag from running the oil cooler. If so, no wonder why they went with electric steering to get rid of that pulley as well.
I think the oil flows through the oil cooler all the time, and it gets adjusted for more flow in Sport setting. It is an oil to water radiator and given that it is well lubricated :-) I doubt that the difference creates enough "drag" to affect MPG. More likely it is done to improve warm up time and meet specific demands of the emisions regulations.
 
Old Nov 12, 2013 | 09:53 AM
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Thats interesting on the highway MPG.
How are you measuting MPG?
I am fairly certian the PCM is not accurate.
 
Old Nov 12, 2013 | 09:55 AM
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PCM highway (7th gear mostly) at speed limit getting 27-28 MPG. 8K ODO
 
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