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Old 10-06-2017, 11:05 AM   #41
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Yes, That's true. Diesel is more like 40-50%.
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Old 10-06-2017, 11:52 AM   #42
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It's really dumb for the government to mandate the use of corn based ethanol. What ethanol does is gum up small engines, personality I would pay more for gas to take ethanol out of regular gas instead of premium gas. Corn based ethanol was a dumb idea to get rid of excess corn, I can see ethanol is a good idea if it's made from sugar cane
Ethanol is the same regardless if it comes from corn or sugar cane.
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Old 10-06-2017, 12:02 PM   #43
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It cost less to make from sugar cane
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Old 10-06-2017, 12:27 PM   #44
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Good thing about driving up mountains... the octane requirement is actually lower due to altitude. That's the reason octane number of fuel that you buy at high altitude locations is actually lower by a couple points on purpose.
Bingo! I knew if I followed this thread far enough that someone would get it right. At higher altitude with lower air density, the charge density in the cylinder (at full throttle) is lower (similar to having a lower compression ratio), requiring less octane to prevent detonation. Detonation occurs when the pressure (ahead of the flame front) at the far end of the combustion chamber reaches the point where compression ignition occurs (like in a diesel) due to high enough temperature. The remaining mixture goes off with a big violent bang, rather than the smooth burning that would result from the flame front reaching the end of the chamber first. This results in really high pressure and temperature in the cylinder, that can cause damage. Higher octane prevents detonation by increasing the temperature point required for self ignition of the remaining charge in the cylinder. Higher octane has no other benefit and does not increase the energy content of the fuel. If today's engines detonate, the control system retards the timing or richens the mixture, both of which will reduce fuel economy, so the fuel price vs economy is perhaps a wash. Any advantage of higher octane probably relates to the peak power loss avoided by not derating the engine due to detonation.
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Old 10-06-2017, 01:14 PM   #45
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Bingo! I knew if I followed this thread far enough that someone would get it right.
It helps that I was an EE for GM many years back and worked with the ECU. So much mis-information in this thread.
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Old 10-06-2017, 03:41 PM   #46
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Don't waste your money. Regular works fin in my F-150 with either towing or not.
Premium would be a waste of money from my experience.


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Old 10-07-2017, 12:15 PM   #47
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People with more time ontheir hands than I do have put tohether a spread sheet thats yakes into account cost per gallon, miles pergallon
Run three tanks ofbeah during typical daily driving. There was a slight (?) difference in cost. I think the costpergallon out weighed the mpg inc
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Old 10-07-2017, 05:07 PM   #48
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I still think if you want good gas mileage buy a bicycle.




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Old 10-07-2017, 08:47 PM   #49
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My Silverado 1500 says Premium Recommended. I suppose so since the compression ratio is 11.0:1. I get 2 - 4 mpg more with Premium than I was getting burning Regular with a 5.3L. Think I'll stay with Premium. Besides, I averaged 11-12 mpg going into the mountains in September and 10-11 mpg on the way home pulling in quartering head and crosswinds with strong gusts.
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Old 10-07-2017, 10:07 PM   #50
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My rv can use e0-e15 max. I mostly stick with 87 gas. A few places in my travels had e85 and 86 regular. I had never seen any gas lower than 87. The 86 gas was straight gas no ethanol and was cheaper than the e85. I went with the 86 regular. 100 octane unleaded is around $5.00. Leaded 110 octane is about $7.00. 87 octane withethanol is about $2.20.
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Old 10-07-2017, 10:31 PM   #51
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I do my own oil changes so it's needless to say I hang onto them until the next oil change.
Out of curiosity, how and why does doing your own oil changes determine how long you keep the receipts?
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Old 10-07-2017, 10:40 PM   #52
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A resource for locating ethanol-free gasoline, if interested:

www.pure-gas.org
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Old 10-08-2017, 05:09 AM   #53
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Good thing about driving up mountains... the octane requirement is actually lower due to altitude. That's the reason octane number of fuel that you buy at high altitude locations is actually lower by a couple points on purpose.
I don't think that is true in the case of a turbo'd engine like the Ecoboost Ford. It is totally unaffected by elevation related horsepower loss. The "air pressure" in the engine is determined by the turbos. I have a boost gauge and can tell you that, sea level or 10,000 feet above, the pressure to the engine is the same. So, fuel octane requirement is the same.

I've tried premium in my Ecoboost. The only thing that I notice is that it holds its gears better before deciding to downshift with premium. There is no discernible difference in power or fuel mileage. I run 87 all of the time. When buying gas at altitude, that sometimes means buying premium. The 87 octane minimum is still required because of the turbos.
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Old 10-08-2017, 09:27 AM   #54
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I don't think that is true in the case of a turbo'd engine like the Ecoboost Ford. It is totally unaffected by elevation related horsepower loss.
In theory you would think that. The reality is that let's say at 7000 feet which are mountain passes I go over, the boost to compensate for the less dense air would be over a 35% increase. The ECUs never let that happen. The problem is the turbocharger gets hotter, the air it is pumping gets hotter and an intercooler, if the air is that much hotter, don't work efficiently.
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Old 10-08-2017, 03:30 PM   #55
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In theory you would think that. The reality is that let's say at 7000 feet which are mountain passes I go over, the boost to compensate for the less dense air would be over a 35% increase. The ECUs never let that happen. The problem is the turbocharger gets hotter, the air it is pumping gets hotter and an intercooler, if the air is that much hotter, don't work efficiently.
So are you saying the theory is wrong or right? You may not gain back 100% of what was lost with altitude but you will gain back most of it. That's the beauty of turbos, You don't have to stop at 7000 feet, it applies much greater in aircraft at 25,000 feet. The turbo or supercharger puts back what is lost. You usually also don't run into a heat soaking problem the higher you go because you get a nice drop in temperature at those elevations, also you are talking passes which are short lived and the cooling system can handle the temporary increase in work load.

So it may not be totally unaffected, but greatly less effected to the point where you would never tell from the driver's seat. Now load up a non turbo motor at sea level and take it up to high elevation and you will feel it in seat of you pants the power loss is so great. For a long time I think this is what gave diesels such a great advantage. It wasn't so much the diesel part as it was the turbo part. Now that we have turbo gas motors we see much of the advantage is in the turbo not the fuel. The fuel helps as well but can you imagine the power a 6.7 liter gas motor with a nice turbo system would make? probably 7-800hp. Diesels are nice but the magic is in the turbo.
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Old 10-08-2017, 08:09 PM   #56
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So are you saying the theory is wrong or right?
We were talking about whether the octane requirement goes down or not at high altitude. Because the engine manufacturer doesn't let the boost make up for the thinner air, the requirement for octane still is lower.

Has nothing to do with the heat capacity of the engine cooling...has to do with the density of the air being heated up. Hot air is less dense.
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Old 10-10-2017, 04:24 PM   #57
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We were talking about whether the octane requirement goes down or not at high altitude. Because the engine manufacturer doesn't let the boost make up for the thinner air, the requirement for octane still is lower.

Has nothing to do with the heat capacity of the engine cooling...has to do with the density of the air being heated up. Hot air is less dense.
Ok, I got you. I thought you were disputing the fact turbos handle altitude better than natural aspiration.
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Old 10-10-2017, 04:30 PM   #58
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Ok, I got you. I thought you were disputing the fact turbos handle altitude better than natural aspiration.
Nope. Problem is with the F-150 and most production vehicles, you never get 100% of the power back due to limitations of boost that the manufacturers dial in.
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Old 10-10-2017, 10:02 PM   #59
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Turbos are great at high altitude especially with Premium. My Silverado 1500 Z71 came with a K&N Cold Air Intake. Combined with Premium (I did use 90 Octane this summer in the mountains of Northern New Mexico), it provides a performance boost for my Naturally Aspirated 6.2L V8. A colleague had put one in his 2009 Silverado and really loved it, so he urged me to have one installed as soon as I bought my 2017 Silverado. When I obtained the build sheet, there it was on the list, already installed. Nice! There is a tremendous difference in performance on Premium compared to my 2014 Tahoe that ran on 87 octane at altitudes above 7000 feet towing a 6000# trailer. I'll stick with Premium and get the mileage and power boost.
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Old 10-11-2017, 06:22 AM   #60
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2015 f150 eco with a tune, 93 everyday. I'd never let an engine knock, even with sensors, if you knock and it pulls timing, it will put the timing back until it knocks again. It will do this over and over. Knocking is never good. Rings will burn, Pistons will melt, rods can break, valves can bend or damage the seat. Just letting the computer monitor it just means it lets it knock, senses it, pulls timing, waits for a few seconds and puts the timing back until it knocks again. I suppose it's not bad if you only have the vehicle for a few years and sell it .... Make it someone else's problem.
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