dougbattaglia

We have seen that the EPA listing is 14L/100 km in city driving and we are continually at 12 or 13L/100 km. I like, what else can I say.

beach_boardz

I am normally at 15 ish in city now around 13 city and was around 11-12 highway now 9.5-10

SultanGris

The reason people don't see a difference is because there is no difference unless the ethanol level is different. People seeing a difference are either clueless as to ethanol content or are simply just driving differently and not realizing it.

dcalicotte03

50 hp?!? My manu says 15 I believe. 2010 5.4

SultanGris

I swear mine said 50 but I read it two years ago, maybe I was wrong, my bad! 2010 5.4 also

Lost In Sync

Mileage is very important to me because of how much I use my truck. 2013 EB 3.55 Supercab XLT 6.5 bed with 17" tires. Bought in October of 2012. Currently the truck has over 25,000 miles on it.

My average mile per gallon is crazy high compared to a lot of others. I check my mileage with the dash gauge and by hand with every fill up.

I've done four trips to San Francisco from San Diego and back. Some of the trips included Sacramento. After a few days and more than twenty business stops I'll be over 22mpg when I get home. That's at 65 mph. No faster. At 80mph it'll still be between 19 and 21 when I get home.

I only use top tier fuels, Chevron, Shell, Texaco, 76, Mobil and Exxon. When I've used off brands the mileage suffers by 3 to 5 mpg.

I've used premium from the top tier stations and have not seen any difference in my mileage. I drive easy on the throttle but I will get up to cruising speed in a normal way, not hard on the throttle but not easy either.

Premium doesn't help my truck at all. Never used the truck for towing, at least not yet, so that's not a factor for me.

jonbar87

I believe it could be 50. What I couldn't believe is how much power 1 degree of timing makes, and this is with a 9.0:1 CR. Awhile back, I was tuning an 04 S2000 and started out with 5* of timing @ 23psi. Every run, I increased timing by 1*. I did this 5 times until it quit making power. Below are the dyno graphs...the results speak for themselves. Very interesting if you ask me:

First 5 runs:
5* @ 23 psi
1st run: 415hp/285 ft lbs tq
added 1*
2nd run: 455hp/294 ft lbs tq
added 1*
3rd run: 462hp/305 ft lbs tq
added 1*
4th run: 467hp/312 ft lbs tq
added 1*
5th run: 470hp/320 ft lbs tq


added 1*
6th and final run. It quit making power after this so I left it here: 477hp/329 ft lbs tq


Ignition timing is key when it comes to an engine's power/efficiency.

dougbattaglia

Just shows the engineers know what they are doing, under heavy load high temp like towing if you keep the timing up and away from the knock retard it will make more power.

engineermike

For lack of a truly controlled test, I will post some technical information and observations:

1) Energy density (BTU content) is not necessarily related to detonation resistance. In other words, high octane doesn't equate to high energy.
2) Amongst gasolines with the same ethanol content, the energy density, specific gravity, stoichiometric ratio, flame front speed, and RVP are all very nearly the same.
3) In light of the above, the only way lower octane can reduce economy or power is if it knocks and retards timing on regular but not on premium fuel.
4) (This is important) there is something called Max Brake Torque timing - that is the optimum ignition advance at any given load and speed, which achieves the highest torque/lowest BSFC, knock notwithstanding. MBT timing has been reduced dramatically over the years due to combustion chamber advancements. So, it is quite common for MBT timing to be a number below the knock threshold. In other words, the engine may be most efficient at 20 deg advance (highly optimized chambers can make best power/efficiency running <10 deg btdc), while it may not experience knock until 30 deg. Advancing to, say, 25 deg will only reducing efficiency, so the ecu's don't attempt to do that. The old adage that you advance timing til it knocks then back off a little is no longer true.
5) Those who have logged these new trucks have reported that they only seem to need knock retard in extreme conditions, not typical everyday driving.
6) Aftermarket tuners find power, even on regular fuel. This is done with more aggressive tuning, including but not limited to. . .more timing advance (as "News in" suggested). This would not be possible if the factory tune was already pulling timing due to knock.
7) The 11.0/1 compression mustang has a dual power rating based on octane (+2.5% on premium) while the 10.5/1 truck does not. Even if this +2.5% happened in normal driving (it won't) and it affected the truck the same way (it won't), it would only improve economy by about 0.5 mpg.
8) E10 has 5% less energy density than pure gas, which will result in a commensurate drop in mileage.
9) In some places, premium is pure gas while regular is E10. This, of course, invalidates those comparisons.
10) The Owner's manual says premium will improve performance in severe conditions, but does not go into much detail defining what "severe" means. However, we know that the trucks have to be designed to tow max capacity in the most severe ambient conditions, such as 120 deg heat. If someone tells me they noticed improved mileage and power on premium while towing 10,000 lb up a mountain when it's 120 F outside, they'll get no argument here.
11) There are far too many uncontrolled variables in ordinary driving to get an accurate assessment of a change, not the least of which is placebo effect. Traffic, red lights, cars leading or following (>10%), summer vs winter fuel (2%), driving style (as SultanGris suggested) (30%), ambient temperature (25%), humidity, wind, elevation change, etc. all come into play when testing and its nearly impossible to control all of them. Just look at this thread, for instance...widely varying results which can only mean one thing: our testing method SUCKS!
12) I, personally, got 23.7 mpg (ecoboost, but the 5.0 would be similar) over 2400 mostly interstate miles on 87 octane, mostly E10. I firmly believe this would have been 24.5 if I had run pure gas. Some are claiming as much as a 15% improvement on premium. Does anyone really believe this would have been 28 mpg (24.5 * 1.15) if I had run premium? I don't.
13) E85 is a different fuel altogether, and really just confuses the issue. The specific gravity, heat of vaporization, btu content, stoichiometric ratio, etc. are all very different, so it's really a different discussion.

Draw your own conclusion based on the above. I sincerely hope someone finds it useful.

Edit: In conclusion, if you drive normally or slower in moderate or cool climates, then you're not likely to experience a change in mileage with octane. If you drive for extended periods at WOT, tow a lot at heavy loads, and/or run in very hot climates, then you could gain up to .5 mpg. However, there is really no good way to control the test well enough to accurately measure this, plus you would have to scrub placebo effect out of it.

News in

I'm still not sure the ECM advances timing for a higher octane fuel. Don't know for sure, it might. But making more hp on E85 doesn't imply the timing was advanced. You get lower mpg's on E85, and make more hp. So that would make me think it burns faster or hotter than gasoline. Thereby making more power. Sort of like if you put a shot of nitrous in an old 350. There's no sensor doing anything, just more available power because of the different fuel. So maybe the added hp on E85 is due to the way E85 burns compared to gasoline, rather than the ECM doing anything fancy. Or maybe not, I'm just kind of thinking out loud. I'm not an ethanol fuel expert. I just know it screws up my chainsaw if I let it sit in there long without running it lol.