Amazing MPG Improvement Without Corn (N/A)

[Cpt_Kirk]

Why don't you all grab your McDonald's, large coke, motorized scooter, oxygen, and have a race to settle this once and for all.

You're going to pay the exhorberant gas prices anyway.

 

[timwinters]

Mathematically, gasoline with 10% ethanol will have about 5% less energy per unit. I do not see how you can increase mileage more than the BTU content difference.

Run your car with 10% diesel and see what your gas mileage does. Diesel has 13% more BTUs but I'll bet your engine wouldn't like it much!

There's more to it than a simple BTU percentage comparison.

 

[ronnieh]

Good grief, Tim. Diesel engines get considerably better mileage per gallon. The gas engine certainly will not like diesel fuel introduced. Even minute amounts of diesel will greatly reduce the effective octane rating of the gasoline wreaking havoc. Let's keep it apples to apples. Gas mileage is a factor of BTU content. The slightly higher BTU content in certain specialty racing fuels have little if any application in this discussion. The BTU content of pump gasoline is essentially the same with the exception of the amount of ethanol will effect BTU content. 10% ethanol will lower BTU content approximately 5%.

Oxygenated fuels do not have higher BTU's but allow more power to be made much like high barometric pressure or cool air will make more power. More O2 present allows more fuel to be utilized.

I am not a mechanical or chemical engineer nor did I stay at the Holiday Inn last night. I do have some experience in high performance drag engines in another life. Below is a link to a company that in that other life I had some dealings. If what they say differs from what I have said simply ignore what I said. These people are sharp.

http://www.whitfieldoil.com/www/docs/171/vp-racing-fuel-/

I admire the few here that are consistent. They never let things like facts influence what they say. Facts are pesky little things.

 

[RJM62]

Vivid imagination.

Is this imaginary?

Rich

 

[kgruber]

Is this imaginary?

Rich

In your dreams! Garbage in.......Garbage out!

 

[SCCutler]

BTU content will not vary with octane rating in a given group of fuels. Even very high racing fuels (gasoline) will have no appreciable BTU difference, flame temperature or combustion speed. Exception: some gasoline designed for racing applications, high RPM and compression, may have a slightly higher speed of combustion.
Mathematically, gasoline with 10% ethanol will have about 5% less energy per unit. I do not see how you can increase mileage more than the BTU content difference.

Vivid imagination.

It was surprising to me, to be sure, but records maintained over around 110,000 miles supported my conclusion. You can, of course, call me a liar, but I'd advise against it.

 

[ronnieh]

What?? SCCutler, who called you a liar? In fact who even disagreed with you? What a childish threat, you would "advise against it". If somebody did call you a liar what exactly would you do?

 

[flyingcheesehead]

I have also consistently seen about 10% better gas mileage over time with pure gas than with the 10% ethanol blend we usually have.

FWIW, my BIL is a chemist in the fuel industry. He was not surprised at this result, and when I asked what he thought about the contribution of the higher octane vs. the lack of ethanol, he also said that the octane doesn't really make a difference - It's the corn.

http://pure-gas.org/

 

[Sac Arrow]

Ethanol both reduces the energy content of the fuel due to less liquid energy density, and also increases the effective octane. You can normally run an engine designed for 91 on 87 octane E10 or E15 blend no problem, as in you won't activate the adaptive timing system if you have one.

By the way, did the OP compare his mileage on the same hilly road? You actually can get better mileage over hilly terrain - when you're going uphill, your engine is running closer to peak efficiency due to the high power loading and more open throttle setting, while burning minimal fuel at idle on the downhill. The energy expended going uphill is recoverable I consistently get better mileage through the foothills than I do on flat land.

 

[SCCutler]

What?? SCCutler, who called you a liar? In fact who even disagreed with you? What a childish threat, you would "advise against it". If somebody did call you a liar what exactly would you do?

1. No one.
2. No one.
3. No threat made.
4. Nothing at all.

 

[MAKG1]

Ethanol both reduces the energy content of the fuel due to less liquid energy density, and also increases the effective octane. You can normally run an engine designed for 91 on 87 octane E10 or E15 blend no problem, as in you won't activate the adaptive timing system if you have one.

By the way, did the OP compare his mileage on the same hilly road? You actually can get better mileage over hilly terrain - when you're going uphill, your engine is running closer to peak efficiency due to the high power loading and more open throttle setting, while burning minimal fuel at idle on the downhill. The energy expended going uphill is recoverable I consistently get better mileage through the foothills than I do on flat land.

Hilly, yes, to a point. Not curvy if you live in the mountains and are actually trying to get somewhere.

Those tend to go together unless you're on an interstate.

And all bets are off when you start using your brakes or low gear to control your speed, unless you drive a good hybrid.

 

[RJM62]

Ethanol both reduces the energy content of the fuel due to less liquid energy density, and also increases the effective octane. You can normally run an engine designed for 91 on 87 octane E10 or E15 blend no problem, as in you won't activate the adaptive timing system if you have one.

By the way, did the OP compare his mileage on the same hilly road? You actually can get better mileage over hilly terrain - when you're going uphill, your engine is running closer to peak efficiency due to the high power loading and more open throttle setting, while burning minimal fuel at idle on the downhill. The energy expended going uphill is recoverable I consistently get better mileage through the foothills than I do on flat land.

I live in the Catskills. Anywhere I go is a hilly drive.

I didn't take the same road on the return trip as I took on the trip out, but it was a road I do use regularly. Both are equally hilly, with about a 1,200 foot climb in the middle over the mountain, but almost the exact elevations on either end. They're also both very twisty, necessitating frequent speed reductions around the turns.

The only real difference between the two roads is that the one I used on the return trip is about three miles longer and goes through a couple of sleepy villages, so it adds maybe eight to ten minutes to the trip. But it also has a lower deer hazard, making it a better choice at dusk; and because of the villages, it has slightly better cell phone coverage and would make for a shorter walk to civilization if I were to get into an accident.

Basically, during the daylight hours in good weather, I take the shorter route to shave a few minutes off the time. From dusk to dawn or in bad weather I take the longer one for safety reasons. I doubt the car's engine cares very much which one I take. They're pretty much the same in terms of things an engine would care about.

I understand, agree with, and have also experienced the improved mileage on hilly roads in general. I also believe that if the higher octane helps at all MPG-wise, that's where it happens: going uphill. It prevents the timing from being retarded. That's about the only way higher octane in itself contributes to better MPG. But because that's a big part of my driving, I want to make a comparison with 91-octane corn-laced.

The other thing I have to consider economy-wise is that I get lower prices at Sunoco because of the deal they have with Price Chopper (a regional supermarket chain). At present I've accumulated a $0.57 / gallon discount on Sunoco gas based on routine grocery purchases at Price Chopper. (It goes back down to zero every time you fill up.) But I'd have to go to Mirabito for the ethanol-free, so I'd lose the Sunoco discount.

If I do decide to switch to ethanol-free all the time, I'll just have my dad get Price Chopper to issue me a loyalty card on his account so he gets the Sunoco discounts on my grocery purchases. Hey, someone may as well get them, and it may as well be dad.

Rich

 

[MAKG1]

The braking is a bigger variable. It means your speeds were all over the place, and accelerations were even worse.

If you want to draw any conclusions at all from this, you'll need to control some variables. Can you even tell us the sampling interval and the window for your instant MPG measurements? I can come up with some combinations that would undercount jackrabbit starts quite badly.

You can also suppress timing redardation by using a lower gear.

 

[RJM62]

The braking is a bigger variable. It means your speeds were all over the place, and accelerations were even worse.

If you want to draw any conclusions at all from this, you'll need to control some variables. Can you even tell us the sampling interval and the window for your instant MPG measurements? I can come up with some combinations that would undercount jackrabbit starts quite badly.

You can also suppress timing redardation by using a lower gear.

I think the interval is ten seconds. I'll have to look it up, but it's pretty frequent, I can say that much. I zero it out at every fill-up, so the average it displays is for that particular tank.

I've also compared the car's displayed MPG to my calculated MPG on every tank since I bought the car -- I'm a bit of a hypermiler at heart -- and it's never been more than 1/2 MPG off. Because I don't top off, there probably are considerable differences in how full the tank is when the pump stops each time I fill up; so I suspect that the car's computer is actually much more accurate than my own measurements.

The variable that's impossible to control right now is the temperature. It's all over the place this time of year. The range this week is expected to be from 69 to 27. I'm also told that rain on the road reduces MPG, although I've long since forgotten the details of why it does. Probably by increasing roll resistance, if I had to guess.

In every other way, my overall driving from tank to tank is pretty consistent. Comparing the averages for each fill-up will give me at least a ballpark idea, especially if I always choose the longer route over the mountain for the weekly credit union / supermarket run. They're within 1/4 mile of each other, so I always combine the trip.

Rich

 

[RJM62]

According to the manual, the MPG display appears to update every 0.03 miles (50 meters).

Rich

 

[MAKG1]

The car's computer has an overall fudge factor -- the injector flow rate. The tolerances for that can be looser than you like.

Unless your car is slow, your accelerations don't take much longer than 10 seconds, right? I'd want sampling at least twice as fast as the HEGO switch rate, which is usually a few Hz, with a window perhaps up to a minute.

I get 20% variation in mileage on the same route with the same fuel. Mountains are seldom driven the same way every time. Conditions just don't allow that.

 

[MAKG1]

According to the manual, the MPG display appears to update every 0.03 miles (50 meters).

Rich

So if you're stopped, the mileage is not zero?

Good thing it's not critical.

Display update and sampling are not the same, but that's a pretty bad error.

 

[MAKG1]

The variable that's impossible to control right now is the temperature. It's all over the place this time of year. The range this week is expected to be from 69 to 27.

Check your TIRE PRESSURE. I think it's low in the cold.

It can make a big difference in mileage if it's severely low.

Intake temperature is usually regulated in cars at part throttle. 80 deg F is a common setting.

 

[Capt. Geoffrey Thorpe]

My variation in gas mileage over a reasonable period.

 

[dell30rb]

I get 20% variation in mileage on the same route with the same fuel. Mountains are seldom driven the same way every time. Conditions just don't allow that.

FWIW the 15-18% improvement I listed was on cruise control at the same speeds over a 35 mile flat highway route with very little traffic. On approx the same temperature days.

I hit the reset on the MPG counter once I hit the on-ramp to the highway, and recorded the MPG once I hit the stop sign at the top of the off ramp 35 miles down the road. Summer with AC running the whole trip.

Got between 25-26 mpg over three runs with non-ethanol premium fuel. 10% ethanol premium fuel was a hair under 22mpg.

Vehicle is a 2004 Acura. It was designed before ethanol came on the scene. I wonder if newer vehicles have less of an MPG drop on E0 vs E10 fuel.

I'd love to see someone do a real scientific experiment on this. I did my best. I think those MPG readings are accurate, I have tested the car's MPG calculator over a full tank of gas, and the car only took .2 more gallons than the calculator said it would to fill the tank.

If you think of the loss in MPG, and the amount of damage done to personal property (boats, lawn mowers, etc..) over the years, the damage to our economy probably equals a major natural disaster.

 

[RJM62]

So if you're stopped, the mileage is not zero?

Good thing it's not critical.

Display update and sampling are not the same, but that's a pretty bad error.

It's zero when stopped after reset and will stay at zero until the car starts moving. After that initial movement it will not display zero again until the next time it's cleared because the display is of the average MPG since the last reset, not the current MPG.

The manual doesn't provide detailed information about how the system works. It does say that to obtain an accurate reading, the car has to be driven at least 0.03 miles (50 meters). That why I said that that appeared to be the sampling interval. So I guess the only thing that can be said for sure is that the interval is no longer than that. It could be shorter, or it could be time-based rather than distance-based.

The display itself seems to update about once every ten seconds, but I'd have to have a passenger time it while coasting down a hill very shortly after a reset to know for sure. That's the only time and operating condition during which the average since the last refill/reset would change rapidly enough to be reasonably certain that the changes on the display were happening at the minimum display update interval.

Rich

 

[RJM62]

Check your TIRE PRESSURE. I think it's low in the cold.

It can make a big difference in mileage if it's severely low.

Intake temperature is usually regulated in cars at part throttle. 80 deg F is a common setting.

Right. But the difference would be in the direction of low MPG with under-inflated tires, no?

I will need to check the pressure again later this week, however. I inflated them to 37 on the 15th when the snows were mounted, per the manual, which specifies 4 PSI over the doorpost pressure for snow tires. (I have no idea why. Do you, perchance?) But the temperature's going to be in the 20's or 30's by the end of this week, so I'll be needing to add some more air.

Rich

 

[RJM62]

My variation in gas mileage over a reasonable period.

That's cool. Thanks. I'm glad I'm not the only one who's anal about tracking MPG.

Rich

 

[RJM62]

FWIW the 15-18% improvement I listed was on cruise control at the same speeds over a 35 mile flat highway route with very little traffic. On approx the same temperature days.

I hit the reset on the MPG counter once I hit the on-ramp to the highway, and recorded the MPG once I hit the stop sign at the top of the off ramp 35 miles down the road. Summer with AC running the whole trip.

Got between 25-26 mpg over three runs with non-ethanol premium fuel. 10% ethanol premium fuel was a hair under 22mpg.

Vehicle is a 2004 Acura. It was designed before ethanol came on the scene. I wonder if newer vehicles have less of an MPG drop on E0 vs E10 fuel.

I'd love to see someone do a real scientific experiment on this. I did my best. I think those MPG readings are accurate, I have tested the car's MPG calculator over a full tank of gas, and the car only took .2 more gallons than the calculator said it would to fill the tank.

If you think of the loss in MPG, and the amount of damage done to personal property (boats, lawn mowers, etc..) over the years, the damage to our economy probably equals a major natural disaster.

Not to mention increasing world hunger due to skyrocketing commodity prices because we're burning food in our tanks.

Rich

 

[dell30rb]

Temperature alone shouldn't affect how efficient the engine is. If its 95F vs 20F the air/fuel mixture is the same. For highway traveling anyway. If you are heavily loaded and having to give it a bunch of throttle to accelerate out of stoplights, your computer will enrich the mixture during those higher throttle settings, essentially going from best economy to best power mixture.

I'd think cars would be more efficient at highway speeds on the hot days. Air is less dense and tires really heat up on a hot summer day. OTOH you are probably running AC which does cost maybe 5% fuel economy


This seems like a pretty good device for tracking your MPG and fuel spending. I like that it automatically figures how much you are spending on fuel by tracking your local average fuel price at the time of fill -ups

www.automatic.com

 

[JoseCuervo]

Not to mention increasing world hunger due to skyrocketing commodity prices because we're burning food in our tanks.

Rich

Corn is $2-3 per bushel.

That ain't skyrocketing.

Farmers are crying.

 

[Capt. Geoffrey Thorpe]

The manual doesn't provide detailed information about how the system works. It does say that to obtain an accurate reading, the car has to be driven at least 0.03 miles (50 meters). That why I said that that appeared to be the sampling interval. So I guess the only thing that can be said for sure is that the interval is no longer than that. It could be shorter, or it could be time-based rather than distance-based.

I would guess (based on how brand F works) that the "sample interval" is about the same rate as injector events. Cumulative sums of how much fuel is burned may be uploaded to the instrument panel several times per second.

 

[RJM62]

Okay, I filled up this morning with Sunoco 91-octane corn-laced fuel. At that time, my indicated MPG from the last fill-up (with ethanol-free 91) was 38.1, and my calculated MPG was 37.8. So I'll call it 38. So the improvement from the previous fill-up (31.8 MPG using corn-laced winter-blend 87) was about 6 MPG over about 380 miles of driving.

The route I took today from the gas station to my home was the same one I took when I filled up with the ethanol-free (the two stations are across the street from each other) and the car was similarly loaded. The temperature today was about 20 degrees cooler. My indicated MPG upon arriving home today was 37.6, versus 42.8 for the same trip using the ethanol-free. The average MPG will, of course, go down before the next fill-up with local running around. I mention today's reading just for comparison's sake.

Based on the MPG since the last fill-up and the relative pricing, the MPG benefits of the ethanol-free gas versus the price results in a cost difference of less than a penny per mile. There's also no noticeable performance improvement using the ethanol-free 91 versus the corn-laced 91. They both handle the hills pretty much the same (and either provide a significant and noticeable performance improvement over the 87).

The ethanol free is better for the engine's and fuel system's health, however. How much better it is than corn-laced plus STA-BIL is debatable: The Marine STA-BIL does a reasonably good job of mitigating the harmful effects of ethanol. But no ethanol is still better than ethanol plus a damage-mitigating additive. Also, I don't need the STA-BIL (which is pretty pricey) at all with the corn-free, so it would make sense to just go ahead and use the ethanol-free:

EXCEPT that I also have to consider the loss of the Price Chopper discount. With this morning's grocery purchases, my savings per gallon totaled $0.90, or roughly $9.00 on today's fill-up. Also, the nearest Mirabito station where I can buy ethanol-free is 27.4 miles away, but there are Sunoco stations everywhere. It wouldn't pay to drive 54.8 miles just to buy gas when the cost per mile is basically a wash.

Sooo... what I suppose I'll do is buy the ethanol-free when I happen to need gas when I'm close to the Mirabito station, and when I don't have a significant Price Chopper / Suncoco discount accumulated. Otherwise, I'll buy the Sunoco 91. This will probably work out to alternating every other tank full.

Rich