Gas Grade and Mileage

SouthArk370Z · 03-31-2013, 07:52 PM

Quote:

Originally Posted by RoshDawg

Something interesting, Porsche (at least on the 991) runs temps of 210-220 for oil when in normal mode to reduce emissions and in turn (I think) increase gas mileage. When selecting sport, oil temp goes down to 180.

Higher oil temp apparently has something to do with emissions.

From what I have read about some of the MPG contests, higher engine temps = better MPG. Something to do with keeping the combustion gases as hot as possible while in the cylinder for maximum efficiency. IIRC, ∆T and heat loss rate were thrown in there.

RoshDawg · 03-31-2013, 09:17 PM

Quote:

Originally Posted by SouthArk370Z

From what I have read about some of the MPG contests, higher engine temps = better MPG. Something to do with keeping the combustion gases as hot as possible while in the cylinder for maximum efficiency. IIRC, ∆T and heat loss rate were thrown in there.

Nice that makes sense. Judging from your other posts I take it you're an engineer? If so, what kind?

Oh and op, use 91 at least.

SouthArk370Z · 03-31-2013, 10:14 PM

Quote:

Originally Posted by RoshDawg

Nice that makes sense. Judging from your other posts I take it you're an engineer? If so, what kind?

Oh and op, use 91 at least.

Not an engineer but spent many years as an Instrument Tech at a hazmat incinerator, so I know a little bit about combustion and heat. I also paid attention in Science classes when attending high school.

I also spent some time in mechanical maintenance, so have been around pumps, valves, flow, &c.
I was always asking the engineers "Why'd ya do it that way?" and most of them LOVE to splain stuff to others. heehee

RoshDawg · 04-01-2013, 01:04 AM

Quote:

Originally Posted by SouthArk370Z

Not an engineer but spent many years as an Instrument Tech at a hazmat incinerator, so I know a little bit about combustion and heat. I also paid attention in Science classes when attending high school.

I also spent some time in mechanical maintenance, so have been around pumps, valves, flow, &c.
I was always asking the engineers "Why'd ya do it that way?" and most of them LOVE to splain stuff to others. heehee

Nice! Haha spot on!

EndyKwon · 04-01-2013, 03:04 AM

Quote:

Originally Posted by RoshDawg

Something interesting, Porsche (at least on the 991) runs temps of 210-220 for oil when in normal mode to reduce emissions and in turn (I think) increase gas mileage. When selecting sport, oil temp goes down to 180.

Higher oil temp apparently has something to do with emissions.

So running an oil cooler would make the engine run less efficiently as far as MPG goes?

KERMIT · 04-01-2013, 09:18 AM

Quote:

Originally Posted by EndyKwon

So running an oil cooler would make the engine run less efficiently as far as MPG goes?

Heat energy flows from hot to cold and based on the difference in temperature from one side to the other (delta T) and the material properties, it will determine how fast energy is transmitted through the material.

That being said, the heat energy is generated by fuel energy. You want to have more of that energy end up turning your crankshaft as opposed to going into the atmosphere as heat. Running hotter reduces the delta T in the combustion chamber allowing more of the heat to stay in as opposed to going into the coolant. (this is super basic overview).

as a rule of thumb your fuel energy is 30% crankshaft power, 30% cooling losses, 30% exhaust, and 10% friction.

What they are attempting to do with running hotter is take some of the cooling % and put it back into crankshaft power. We are talking very small amounts... but every bit helps to meet the future regulations.

SouthArk370Z · 04-01-2013, 10:05 AM

Quote:

Originally Posted by EndyKwon

So running an oil cooler would make the engine run less efficiently as far as MPG goes?

Not really. The oil has very little to do with cylinder/gas temps and, as KERMIT points out, the effects of engine temperature on efficiency can be subtle.

It's not really something the average weekend mechanic wants to mess with as there are a lot of other variables involved. Changing the engine temp (eg, by installing higher/lower temp thermostat) can affect how the ECM reacts. Plus there are limits to how far you can go before pre-ignition becomes a problem - especially with a high-compression engine.

USMCASA · 03-31-2013, 08:21 PM

if u want to run cheap gas in a car get a mustang or hybrid

2xtreme1 · 03-31-2013, 09:00 PM

It's like 5$ difference from using 87 instead of 91...
filling up full tank.

BlueDog007 · 03-31-2013, 10:24 PM

I have read a little about FI but not sure what that is. Please explain. Thanks!

Baer383 · 03-31-2013, 10:31 PM

Quote:

Originally Posted by BlueDog007

I have read a little about FI but not sure what that is. Please explain. Thanks!

Forced Induction,as in Superchargers and Turbos

Nismo89 · 04-01-2013, 09:11 AM

Quote:

Originally Posted by BlueDog007

I have read a little about FI but not sure what that is. Please explain. Thanks!

Forced Induction. (in other words) SuperChargers or Turbos.

JARblue · 03-31-2013, 10:44 PM

To save on gas costs, I just siphon gas from my neighbors' lawnmowers

that is, the neighbors I don't borrow gas from for my own lawnmower...

kenchan · 04-01-2013, 01:35 PM

Quote:

Originally Posted by JARblue

To save on gas costs, I just siphon gas from my neighbors' lawnmowers

that is, the neighbors I don't borrow gas from for my own lawnmower...

xxAGAVExx · 04-01-2013, 08:27 AM

Quote:

Originally Posted by EndyKwon

So running an oil cooler would make the engine run less efficiently as far as MPG goes?

That makes a little sense, the viscosity of oil would be affected by the temp, less so with a synthetic, but I think the temp changes would have to be fairly big to see a diff.

03-31-2013, 10:44 PM	#13 (permalink)
JARblue A True Z Fanatic Join Date: Mar 2011 Location: Austin, TX Age: 44 Posts: 36,450 Drives: 11 Z34, 98 E36 M3 Rep Power: 2684441	To save on gas costs, I just siphon gas from my neighbors' lawnmowers that is, the neighbors I don't borrow gas from for my own lawnmower... kenchan, SouthArk370Z and DEpointfive0 like this. __________________ 2011 370Z 6MT Sport Gun Metallic \| ARC \| CJM \| Ecutek \| FI \| Fujimura \| R2C \| SPL \| Stillen \| TWM \| Z1 \| ZSpeed \|

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