Gasoline octane & MPG

[Langwilliams]

I put the 35's on my BB an only lost about 1 mpg. I don't have the gears of course but I think it's fine for me. Being an SUV off road vehicle type I drive it pretty tame IMO but one of my buddy's says I'm a little too aggressive. I told him good thing he neve rides in the work car I drive at work!

FYI I avg about 21.5 winter an 22.5 summer.

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[crenca]

Well, they were posting like 15mpg with e0 and 20mpg with E10, so it was a lot more than 3% difference you would expect. And ... if E10 is 97% of the energy, you would expect the opposite - E0 to be ~better~ MPG, since it has more energy per volume.

I don't really believe such drastic differences can be attributed to amount of ethanol - had to be one or more of the many other variables. According to some experienced tuners I read in the past, ethanol seems to have an outsized effect in the modern turbo engine, past its (very positive) calculable effect on octane. In other words modern turbo engines seem to really like a bit of ethanol, up to the point where it effects injector efficiency (not sure I'm stating this correctly).

Also I recall an article about a decade ago in one of the big zines (Car & Driver maybe??). They compared the cars self reporting vs actual "hand" calculations and found all manufactures padded their numbers, and all were inflated more than 1 mpg if recall correctly - Honda the most. Makes sense if you think about it as what possible incentive do manufactures have to report anything other than something that makes the owner feel good?

Beyond all that, I confess I really don't get all the mpg threads around here...I mean, if your giving more than 3 seconds of concern to gas mileage you bought the wrong car Sell your Bronco and get a Honda, just don't believe its computers reported mpg

 

[Ducati1098]

I don't really believe such drastic differences can be attributed to amount of ethanol - had to be one or more of the many other variables.

Agreed. Certainly not at such a low percentage.
The difference between me running 93 with ~10%, and E85 with ~78% is only about 2-3mpg

 

[MadMan4BamaNATL]

I don't really believe such drastic differences can be attributed to amount of ethanol - had to be one or more of the many other variables. According to some experienced tuners I read in the past, ethanol seems to have an outsized effect in the modern turbo engine, past its (very positive) calculable effect on octane. In other words modern turbo engines seem to really like a bit of ethanol, up to the point where it effects injector efficiency (not sure I'm stating this correctly).

Also I recall an article about a decade ago in one of the big zines (Car & Driver maybe??). They compared the cars self reporting vs actual "hand" calculations and found all manufactures padded their numbers, and all were inflated more than 1 mpg if recall correctly - Honda the most. Makes sense if you think about it as what possible incentive do manufactures have to report anything other than something that makes the owner feel good?

Beyond all that, I confess I really don't get all the mpg threads around here...I mean, if your giving more than 3 seconds of concern to gas mileage you bought the wrong car Sell your Bronco and get a Honda, just don't believe its computers reported mpg

For sure. I mean, I doubt if I’ve ever thought beyond 20 seconds about my MPG except for the one time I was on a trip in the middle of nowhere and couldn’t find a decent gas station to save my life. Got crazy low and was nervous, then found a decent Shell and all was right with the world.

I run 93 because I bought the 2.7 for the power, so why ride around detuned?

I drive a 6K lb 2 Door brick, MPG was obviously not my concern. Approach, break over, departure, and clearance WERE my concern and that’s what I got.

If you bought your off-roader to off-road, daily or toy, that’s what Ford made, they sold and you got it. If for any other reason, you’re not likely to be happy, but that’s on you, not the truck…..

 

[65CarryAll]

Yes, higher octane and E-free gas will increase mileage. Some will do the math and say the increased cost doesn't justify the increase in mileage. That's one way to evaluate it. Another is that by burning less fuel less combustion byproducts and carbon is being produced to build up in the motor and dilute the oil. So in the long term it saves on engine wear. This along with the increase in performance makes it worth it to me.

 

[Fmuguira]

Biggest MPG effect comes from that object you hang your shoe on …. Simple deal.

 

[Tricky Mike]

My hunch is mileage doesn't exactly scale linearly with octane increase and/or ethanol decrease, because the computer is making adjustments to compensate. Anyone that's ever timed an old engine by hand knows that timing can make drastic differences in power and economy.

Still 25% is optimistic, but 10% is probably reasonable. I don't bother with premium when chasing MPGs because it's usually more than 10% more expensive around me.

Sometimes it's the fuel.

A couple of weeks ago I filled up at Walmart because my wife noticed the cheaper price there, then drove from Idaho to Utah. I've taken that particular trip multiple times, but this time I got at least 15% lower mileage than on previous trips. This is one of the few times I couldn't get at least 300 miles out of a tank. When I filled it up in Snowville, the first town inside Utah, the mileage immediately improved.

Coming back I filled up at that same station in Snowville and did 4 mpg better than the trip going there. I think I learned that the 8% cheaper price at Walmart was not worth 15% worse mileage.

All trips through this particular section of road were with the cruise control set at 70 mph with tires inflated to around 38 psi. I drove the same way every time, it was the fuel that made the big difference.

I had a similar experience with Costco gas years ago and swore them off for a long time. In retrospect I think they just got some bad fuel that batch

 

[Brian_B]

I had a similar experience with Costco gas years ago and swore them off for a long time. In retrospect I think they just got some bad fuel that batch

My wife had the same thing happen with the grocery store here. They have the cheapest gas in town with their Member thing (nearest Costco is an hour away). But every time she's tried it (which, is admittedly, not a large sample size), she gets significantly worse mileage in her Bronco Sport such that it isn't worth it.

There's only two stations in town I'll fill up at, and it's a touristy town so it's not cheap even on the best of days, but I have the luxury of having a company fuel card to pay for it. My mileage has always been pretty consistent, with the only "big" change occurring when I upgraded my suspension and gained about half an inch in ride height - and that was only about 1/2 mpg. Even on a ~nearly~ cross country trip with a lot of fillups at various states and stations - still pretty consistent, with the biggest variations depending on head or tail winds.

 

[burgerking]

The ethanol free around here is only 90 octane and it's more expensive than 93. I mix E85 with 89 usually, sometimes with 87. I think I would have more range on straight 93 but it would cost more. I suspect the cost per mile is better with E30 but I don't feel like trying to prove it. Sometimes I put a gallon or two of straight 93 to get me to a station with E85 but that's not enough to really see the MPG change much.

 

[Brian_B]

The ethanol free around here is only 90 octane and it's more expensive than 93. I mix E85 with 89 usually, sometimes with 87. I think I would have more range on straight 93 but it would cost more. I suspect the cost per mile is better with E30 but I don't feel like trying to prove it. Sometimes I put a gallon or two of straight 93 to get me to a station with E85 but that's not enough to really see the MPG change much.

Hmm.

I've never seen a turbocharged FlexFuel vehicle. I don't know what could happen as a result, but it's advised not to run more ethanol than E15. I know some tunes will go higher, for the knock resistance, but that's a bit different and you are using a tune specifically designed for it. I believe the stock ECM is tuned around 87-93 up to E15, and ProCal tune is 91-93, up to E15.



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[usarms]

I have been running Sunoco 93 in my 2.7. When they went to 94 octane I picked up 10 mpg per tank.

 

[DBX2]

The Bronco is not a gas guzzler per say… It’s your foot.

Agreed, speed has a lot to do with it. I turn off Auto Stop/Start with every start up. I use 87 octane exclusively. 2.7 engine. Was getting 20-22 on highway, 18-20 around town until winter - with some warm-ups and the "winter gas" effect. Now at 18 consistently around town and 20 on highway. It is a Tesla? No and surely looks cooler! Slow and enjoy the ride works best.

 

[Ducati1098]

Hmm.

I've never seen a turbocharged FlexFuel vehicle.

The Bronco isn't, but Ford has had a few flex fuel ecoboosts in the past.
Also while the manual says not to use more than 15%, most Ford vehicles have the ability to correct for up to around 30% ethanol without an issue on the stock calibration.

 

[JL8jeff]

I ran 87 octane for the first full year of owning my base 2 door 2.7 Sas and averaged right around 17.9 mpg (with KM3 35's which are 19 lbs heavier than stock). I tried running 93 octane for several months and compared those months to the same months the previous year and the difference was less than .5 mpg. But in between doing that, I added a 3" cat-back exhaust and I'm pretty sure the exhaust accounts for the increase. So there was really no difference in mpg regarding octane. Don't look at the computer calculated mpg, it's always off, you need the raw numbers to get the real mpg. My computer is .6 mpg higher than actual. I did add the Procal tune, Mishimoto intercooler/charge pipes recently and went back to 93 octane but I also went to 37's (which are lighter than the 35's I had) so my ability to do a meaningful mpg calc to compare to stock is long gone.

 

[AZ_Craig]

All trips through this particular section of road were with the cruise control set at 70 mph with tires inflated to around 38 psi. I drove the same way every time, it was the fuel that made the big difference.

Were ambient conditions identical though? Temperature and especially wind direction/speed can have massive impacts. Try doing the same rural drive at 75 mph with a 20 mph tail wind versus a 30 mph head wind.

I remember one time driving my 2012 JKU up towards SLC with winds gusting to around 50 mph straight at me. I struggled to keep above 12 mpg.

The Bronco is a brick. It's going to be similarly prone to this.

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