What octane fuel/petrol do you use?

Big Blue

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You're right it would be dumb to purchase a tune for the sole purpose of gaining a couple extra mpg. It just happens to be an added bonus. Kind of like getting a damper and reaping those extra hp/tq gains. 😜
I was talking about a 30 to 40 percent cost per gallon difference for a 10 percent gain in mileage. Nothing to do with a tune. A tune is a one time cost and a personal choice.





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Racket

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Once a week I'm near a Sunoco that sells E30 which is an unusual blend but 94 octane and 10% cheaper than even the Sam's Club premium- which is typically less than twenty cents more than regular everywhere else. So I alternate topping off now and my MPG's have returned to an average in the mid 19's.
 

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You are not wrong about Colorado and other states run E85 octane for the regular. By myself stupid but apparently the reason for it is 4 old carbureted Vehicles when they're in the High Altitude. Others seem to think that it's okay to run in fuel injection but it's not since they State 87 minimum. With our trucks it does State 87 minimum but for better performance and towing to use 91 and higher. Originally I was running 87 until I made the switch just see and I was able to see an overall performance difference with truck what's the fuel mileage increase. I myself found it to be well worth it.
more about the compression of the engine, standard non performance na motors can run 85 octane because the higher altitude effectively lowers the compression, a turbo engine compensates at higher altitude by adding boost so the octane requirement is the same as at sea level.
 

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more about the compression of the engine, standard non performance na motors can run 85 octane because the higher altitude effectively lowers the compression, a turbo engine compensates at higher altitude by adding boost so the octane requirement is the same as at sea level.
If you can explain to me how elevation affects depression or a shield I believe you. Be aware it's going to take a look because all you did was go up in elevation and nothing inside the engine has changed.
 

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If you can explain to me how elevation affects depression or a shield I believe you. Be aware it's going to take a look because all you did was go up in elevation and nothing inside the engine has changed.
Nothing inside the engine changes so the compression ratio stays the same. The pressure after compression in a NA engine at high altitude is lower because the pressure on the left side of the ratio is lower.
 
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Cost me $112 (CAD) today to fill with 94 octane here in Vancouver today...don't think I can keep that up😲 maybe a little lighter on the throttle!?😆
So in Freedom Dollars that’s like twenty bucks right? (JK. I know it’s about $88 USD). I’m guessing your fuel is about $4 USD/gallon if you’re just shy of $1.30 CAD/liter.
 

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Nothing inside the engine changes so the compression ratio stays the same. The pressure after compression in a NA engine at high altitude is lower because the pressure on the left side of the ratio is lower.
Yeah that still doesn't lower the effective compression ratio because the compression ratio still stays the same. Nwo the air density maybe lower at a high-altitude but it still does not lower the effective compression ratio of the engine at all.
 

Motorpsychology

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Cost me $112 (CAD) today to fill with 94 octane here in Vancouver today...don't think I can keep that up😲 maybe a little lighter on the throttle!?😆
On another forum there was a thread dealing with electric cars and what further incentives could be implemented, noting that in Norway they have twice the per capita electric vehicle ownership than the US (actually it was a thread about the Will Farrel GM commercial during the Super Bowl that got hijacked- never happen here! ;)) Unleaded regular gasoline is the equivalent of $7.22USD/gallon+ and there is no import or VAT tax on electrics and may more. But for me $100 fillups in my Escape would have me looking hard at a BEV.
 

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Yeah that still doesn't lower the effective compression ratio because the compression ratio still stays the same. Nwo the air density maybe lower at a high-altitude but it still does not lower the effective compression ratio of the engine at all.
Again, the ratio doesn't change but the final pressure in the cylinder is lower. If the ambient pressure is 10 psi and the ratio is 1:10 the final pressure is 100psi. If the the ambient is 5psi the final would be 50psi with the same ratio. (Numbers chosen for easy math.) You'd get the same 50psi final pressure if you started with 10psi and had a 1:5 ratio--it's effectively a lower ratio caused by the lower ambient pressure, not by any change in the engine.
 

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Again, the ratio doesn't change but the final pressure in the cylinder is lower. If the ambient pressure is 10 psi and the ratio is 1:10 the final pressure is 100psi. If the the ambient is 5psi the final would be 50psi with the same ratio. (Numbers chosen for easy math.) You'd get the same 50psi final pressure if you started with 10psi and had a 1:5 ratio--it's effectively a lower ratio caused by the lower ambient pressure, not by any change in the engine.
FWIW near the bottom of the page from this link there is a formula that can calculate the approx impact from altitude on the compression, I plugged in 5,000' and a 10:1 ratio and it yields an adjusted effective compression of 9:1 , the key word being effective, compression ratios are taken at sea level, where psi is determined as 14.7 .

https://goodvibesracing.com/Compression_Ratio.htm
 

DT444T

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87. And I tow with it.

I have done the math and it would take over 3 mpg to even out while towing. I get like 11.5 and would need like 14-15 to break even with the cost of 91/93 Octane. She runs just fine.
 
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On another forum there was a thread dealing with electric cars and what further incentives could be implemented, noting that in Norway they have twice the per capita electric vehicle ownership than the US (actually it was a thread about the Will Farrel GM commercial during the Super Bowl that got hijacked- never happen here! ;)) Unleaded regular gasoline is the equivalent of $7.22USD/gallon+ and there is no import or VAT tax on electrics and may more. But for me $100 fillups in my Escape would have me looking hard at a BEV.
Personally, I want hydrogen powered vehicles. I’m not hip on the current recharge times on the fully electric vehicles.
 

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FWIW near the bottom of the page from this link there is a formula that can calculate the approx impact from altitude on the compression, I plugged in 5,000' and a 10:1 ratio and it yields an adjusted effective compression of 9:1 , the key word being effective, compression ratios are taken at sea level, where psi is determined as 14.7 .

https://goodvibesracing.com/Compression_Ratio.htm
So apparently you don't know how compression ratios work. That's okay not everyone does. The only thing that's really going to change when going up in elevation is the level of oxygen. You still have the same amount of air being pumped into the engine. the problem is you don't have the same quantity of oxygen which is needed to fire with the fuel mixture. This causes an extreme rich condition where the fuel has to but cut off quite a bit. That is why naturally aspirated vehicles lose more power over a forced induction vehicle in high-elevation.
 

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The only thing that's really going to change when going up in elevation is the level of oxygen.
Nope. Proportion of oxygen (barring local variation) is the same at sea level as at the top of the mountain--about 20%. It's just that at sea level it's about 14psi and at 10k feet it's at 10psi.

You still have the same amount of air being pumped into the engine.
You have the same volume of air, but since it's at a lower pressure you have fewer molecules of air, including fewer molecules of O2.
 

Trigganometry

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Personally, I want hydrogen powered vehicles. I’m not hip on the current recharge times on the fully electric vehicles.
LNG works nice. We got fleet trucks that run on it. That’s how we get a Raptor Ranger. Make it a 2.7 LNG rig! 😎
 

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