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Guest Message by DevFuse

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Don't waste your money with Premium gas!


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56 replies to this topic

#41 OFFLINE   fbov

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Posted 21 October 2013 - 03:35 PM

First off, Gary, I had a '73 Celica, and your reports of varying mileage with different gas brands would explain a recent trip we took... and it adds another control/noise factor!

 

The one other point is to remember we have Atkinson cycle engines, 12.3:1 compression assumes a 2L intake. at 1.8L, it's more like 11:1 compression, but with a 10% longer power stroke. Conversely, a hybrid engine runs at higher avg. load, so one would expect an adaptive engine to eventually use the added octane productively. It's something to test...

 

HAve fun,

Frank









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#42 OFFLINE   Tree63

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Posted 26 October 2013 - 12:13 PM

In my part of Canada, ethanol is added to Regular (up to 10% in 87 octane) but not to Premium (91).  I don't know if the octane level is maintained with the ethanol added, or if  it is 87 before adding the ethanol and it slips a bit.

 

With my last car (2007 Nissan Sentra), I tried Premium for 6 months and basically saw a 10% FE improvement with a 12-14% price premium.

 

Based on reading earlier postings on the Forum, I decided to try Premium for July-Dec, and am basically seeing the same results (a little behind with Fuelly entries).  (My 600+ tank reported in Forumm was on Regular.)  I'm up to 33000km/20000 miles so well past any break-in considerations.

 

Another factor:  Had the PCM update done about a week ago so too early to add that into the picture, but seemed a bit better on highway trip to the cottage, even with colder weather (mid 30's F) - 5.8 vs 6.2 l/100km at about 110km/hr.

 

Regardless the ride in C-Max is great.

 

ps - tried a tank of "super premium" (octane 94) from a national brand and FE dropped!!  Maybe ECU reprogramming couldn't handle it.


Edited by Tree63, 26 October 2013 - 12:15 PM.


#43 OFFLINE   ptjones

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Posted 26 October 2013 - 02:48 PM

IMO from the Testing I've done Premium does improve MPG's around one or so, but not worth the money.(20-30 cents/gal). Pure gas(90 octane) improves about 2MPG still not worth it.(70-80 cents/gal.)

Paul



#44 OFFLINE   Tdefny

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Posted 26 October 2013 - 04:31 PM

I don't buy into the whole idea of higher octane gas paying off in MPG. Octane rating measures the ability of a fuel to resist detonation (early ignition). Ethanol increases octane rating but decreases mileage, as it is less volatile than gasoline.

A higher compression engine needs the detonation resistance but can get better performance from the higher compression. It needs to detune itself slightly or risk damage if a lower grade of fuel is used. Our Atkinson-Miller cycle engine is more of a high expansion engine. It doesn't use the high compression to get more fuel into a tighter space like a performance engine. Rather, it uses a normal charge and retains it slightly longer to get a little more thermal efficiency.

The energy from fuel comes from breaking carbon bonds and turning them into CO2. Ethanol has fewer carbon bonds and thus less energy. I believe that Ethanol is all they have used to raise octane rating since MTBE was banned, but I am not sure of that.

#45 OFFLINE   ptjones

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Posted 26 October 2013 - 05:03 PM

I don't buy into the whole idea of higher octane gas paying off in MPG. Octane rating measures the ability of a fuel to resist detonation (early ignition). Ethanol increases octane rating but decreases mileage, as it is less volatile than gasoline.

A higher compression engine needs the detonation resistance but can get better performance from the higher compression. It needs to detune itself slightly or risk damage if a lower grade of fuel is used. Our Atkinson-Miller cycle engine is more of a high expansion engine. It doesn't use the high compression to get more fuel into a tighter space like a performance engine. Rather, it uses a normal charge and retains it slightly longer to get a little more thermal efficiency.

The energy from fuel comes from breaking carbon bonds and turning them into CO2. Ethanol has fewer carbon bonds and thus less energy. I believe that Ethanol is all they have used to raise octane rating since MTBE was banned, but I am not sure of that.

They use lead in AVGAS and EPA continues to threaten to ban it,but with no viable replacement  they can't.(it's not a big problem % of volume is small) I'm only using my experience, but for what ever reason all FORD cars That I have owned have gotten better MPG's with Premium over Regular. And it's still not worth the additional cost unless you have need to go farther. Pure gas is the best, but very expensive here.

Paul



#46 OFFLINE   marshtex2

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Posted 28 October 2013 - 12:46 AM

I spent 30 years in fuel research at big ol' Texaco, Product Research, and we looked long and hard into everything about the various grades of fuel.

 

The higher grades of gaso had more aromatics than Regular making them more dense, more mass per unit volume.  The carburetor cars showed better mpg with the higher grades because the carburetor system sucked the gaso over a hump to get it into the metering port.  About the same mass of the more dense fuel was sucked over and that meant less volume.  Hence fewer gallons to go the mile, throttle position staying constant.  That led to all kinds of myths about better mpg with Premium gaso and was great as a selling point for the more profitable product to buyers who didn't need the increased octane rating.  Back with leaded gaso, the lead increased the fuel density, and more lead was in the premium gaso to get the higher octane rating, hence contributing to the better mpg impression.  The volatility of the fuel influenced startablilty and drivability at lower temperatures.  The more volatile components are less dense and would tend to take away from an mpg rating.

 

With the expanded use of fuel injection, which meters the fuel by volume in a sealed system, fuel volatility was less to no influence and the direct effect on mpg went away.  However, the same volume of the more dense fuel means more mass of fuel into each combustion event, hence more power.  A driver looking for fuel economy and pussy footing the throttle pedal can get the desired performance/power with slightly less throttle thereby bringing a little better mpg. 

 

A second however is that most drivers' rampage on the throttle overrides these effects and any improved mpg won't be seen.  It takes very carefully controlled conditions to document these differences.

 

This consideration carries on to ethanol or any oxygenate.  They are less dense than the gasoline hydrocarbon and additionally bring in less energy for their combustion event.  Thus they are detrimental to fuel economy on a per gallon basis at equivalent power settings.

 

Marshall


Edited by marshtex2, 28 October 2013 - 12:57 AM.

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#47 OFFLINE   Swamp45755

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Posted 27 February 2018 - 08:25 AM

I have a 2018 CMax. I tried both regular and premium fuel. The manual states premium gas is preferred. And true to the manual I get better mileage and performance with premium fuel. The CMax sips fuel so unlike my Mercedes which averages 27 mpg, I am currently averaging 41.3 mpg with 1000 miles on the CMax. I suspect my mileage will improve when I clock more mileage on the CMax. I believe the engineers at Ford know what octane works best.

#48 OFFLINE   Swamp45755

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Posted 27 February 2018 - 08:25 AM

I have a 2018 CMax. I tried both regular and premium fuel. The manual states premium gas is preferred. And true to the manual I get better mileage and performance with premium fuel. The CMax sips fuel so unlike my Mercedes which averages 27 mpg, I am currently averaging 41.3 mpg with 1000 miles on the CMax. I suspect my mileage will improve when I clock more mileage on the CMax. I believe the engineers at Ford know what octane works best.

#49 OFFLINE   ptjones

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Posted 27 February 2018 - 10:00 AM

So do CMAX owners. :)  It may not be totally cost effective, but I like the extra range. :) Join fuelly.com  to keep track of your mileage. BTW Odometer is off by 1.6 to 2.2% so you can check with GPS , you will be getting better mpg's than you think.

 

Paul


Edited by ptjones, 27 February 2018 - 10:04 AM.


#50 OFFLINE   MaxHeadroom

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Posted 27 February 2018 - 11:16 AM

2015 C-Max Owner's Manual states:  "Octane Recommendations:   We (Ford) recommend regular unleaded gasoline with a pump (R+M)/2 octane rating of 87. Some stations offer fuels posted as regular with an octane rating below 87, particularly in high altitude areas. We do not recommend fuels with an octane rating below 87. Premium fuel will provide improved performance and is recommended for severe duty usage such as trailer tow."

 

Assuming this is the same wording that Swamp45755 (see a couple of posts above) has in his 2018 C-Max (congrats on your purchase BTW) Owner's Manual, I interpret the statement as you only get an MPG benefit from premium fuel octane only if you drive hard, meaning the engine does sense potential knock and will retard the timing if necessary (when piezo knock sensors detect knock).

Thing is, it won't knock if you aren't driving hard and your engine then doesn't have to retard timing.

 

It is possible it will keep gradually advancing timing (for better MPG) until it senses knock, constantly "hunting" for that optimal timing adjustment as you drive.  Premium gas would allow more advance of timing, giving us slightly better MPG.    I'm not sure if timing advance is there, or if there is much of it, from the baseline engine map though.

Maybe I can figure out if I start seeing advance of timing using the FORScan (Ford-specific smartphone ELM327 OBDII) app.

It could be the Ford engineers actually run the engine on the baseline engine map, and only provide the freedom to retard engine timing (knock sensed), not potentially advance it gradually.  Anybody know if the engine control software algorithms actually do advance timing beyond the stored look-up table engine map value?

 

Biggest fuel problem is ethanol usage.  Ethanol is less energy dense than pure gasoline.  Our C-Max's, like most Fords, can use up to 15% ethanol fuels, E15.  (Can't use E85, the high-ethanol 85% extreme fuel out there.) 

Typical gasoline sold has about 10% ethanol (E10), so we lose about 3% or so MPG (-1.5 MPG) just from the energy density problem with those blends.

Pure gasoline is better for MPG, if you can find it !!



#51 OFFLINE   MaxHeadroom

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Posted 27 February 2018 - 11:35 AM

Some additional research:

https://www.cobbtuni...-ratio-monitor/

discusses how Ford dynamically adjusts timing in their Ecoboost engines.  Maybe applicable to our non-boosted C-Max, not sure.

It does say timing can be advanced AND retarded, both, not just retarded, compared to the baseline engine map tune.

If that's the case in our C-Max, then it is possible to benefit from premium fuel, especially if we accelerate hard or tow.  Owner's manual mentions towing specifically.

 

It may be noted that our engine is most efficient at around 2,000 RPM and about 75% full torque load there.  Using the electric motors to augment the engine means the control system tries to keep the engine running at that specific part-load condition when it can. 

Then it comes down to seeing if the engine can advance the timing at most conditions we drivie at.    We know it freely retards timing when excessivley low-octane gasoline is used, but I'm not sure how much it will actually advance timing when at typical driving RPM & loads.



#52 OFFLINE   ptjones

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Posted 27 February 2018 - 02:24 PM

I have tested this before using ScanGaugeII you can watch the ECM advancing the timing until it detects knocking and retards a little bit. I have seen it go over 40 degrees with high Octane Gas, I have used octane booster to improve MPG's more. I think it added about 2 octane more to a tank, maybe 1 mpg. :) Pure Gas seems to get a little better MPG's than Premium not much, but adding Octane Booster definitely helps.It is also a injector cleaner too. :)  

NOSOctanebooster
It cost about $10 at Walmart.
 
Paul

Edited by ptjones, 27 February 2018 - 02:25 PM.


#53 OFFLINE   ptjones

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Posted 27 February 2018 - 04:17 PM

I checked locally on 100 octane street legal which has some ethanol in it which goes for over $10/ gal ouch! :drop:  cheaper to get ethanol free at $3/gal and add Octane Booster. :)

 

Paul



#54 OFFLINE   SnowStorm

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Posted 27 February 2018 - 08:11 PM

...... Premium fuel will provide improved performance and is recommended for severe duty usage such as trailer tow."

Trailer tow?  Do newer manuals actually state that you can tow a trailer with the C-Max?  If so, what do they actually say?  How many pounds?

Our 2013 printed manual says on page 248 (complete with warning triangle/exclamation mark)

:

TOWING A TRAILER
WARNING:
Never tow a trailer with this vehicle. Your vehicle is
not equipped to tow. No towing packages are available through
an authorized dealer.

 

Has this prohibition been dropped?


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#55 OFFLINE   MaxHeadroom

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Posted 28 February 2018 - 04:46 PM

SnowStorm, towing is banned for all years.   

Still, Ford has never gotten off their lazy rear ends and edited out the mistaken mention of towing, in each model year's manual in about 3 places!   How hard is it to edit out mention of towing?  

Towing isn't available since they would need a better transmission cooling system to handle the extra heat.  Maybe power electronics cooling too.  Engine of course too.

I actually think a 1,000 lb trailer wouldn't be a problem, mounted properly back there of course.  Maybe not towing in the mountains in the summer though.

 

I really wonder what high-torque driving is on the C-Max, especially without towing.  At the full 188 hp, pedal mashed to the floor, is a max torque condition.  Otherwise the engine and motors adjust RPM to be around 75% load, always avoiding knock to some extent just by trying to keep the torque load near that spot.

I drive mine at WOT quite often actually.  Maybe I could gain 1 or 2 MPG from using premium, at a cost of about 10% more of course.

 

 

Owner's Manuals for all model years:



#56 OFFLINE   ptjones

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Posted 28 February 2018 - 06:36 PM

From the standpoint of the ICE, the CMAX is way over cooled, I use Grill Covers all year around. It would put more stress on the trans, probably not a temp problem.  As far as the inverter goes, not sure you can change the amount of use of charging and discharging than normal. :)  I think trans stress would be the main problem.

 

Paul


Edited by ptjones, 28 February 2018 - 06:38 PM.

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#57 OFFLINE   obob

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Posted 01 March 2018 - 04:23 PM

From the standpoint of the ICE, the CMAX is way over cooled, I use Grill Covers all year around. It would put more stress on the trans, probably not a temp problem.  As far as the inverter goes, not sure you can change the amount of use of charging and discharging than normal. :)  I think trans stress would be the main problem.

 

Paul

 

I would think the car would be set up to handle all but the rarest hot conditions.  No manufacturer wants a reputation of their car fails in death valley and then you die of heat stroke.

 

"The hottest air temperature ever recorded in Death Valley was 134 °F (56.7 °C) on July 10, 1913, at Furnace Creek,[16] which is the hottest atmospheric temperature ever recorded on earth.[5] During the heat wave that peaked with that record, five consecutive days reached 129 °F (54 °C) or above. Some meteorologists dispute the accuracy of the 1913 temperature measurement.[17]"   https://en.wikipedia...ki/Death_Valley








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