MPG dilemma....

[salcirabisi]

My wife and I own a home in Florida. We do the snowbird "thing" to rest and relax. Now granted, my wife's concept of "snowbird" is to go to Florida in the teeth of summer, but she explains that we, being a members of an aging populace, need to consider the length of days so we are not driving in the evening (all the while I'm thinking about the 99% humidity and how much the heat will make our visit slightly uncomfortable) since our eyesight presents challenges once the sun sets. Okay fine love!

But, as we are cruising I-65 north on our return trip to Indy I have the cruise control locked at 75 mph and averaging 27.8 mpg. Not bad I think to myself. We stop for a fill up and change of driver and my wife averages 30.4 mpg the rest of the trip. She doesn't use cruise control because as she states, "I want control" of the speed, even though she is always surprised by how well the smart cruise control works when I'm using it. All the while she's cruising at a pretty good clip herself.

Now the explanation is probably obvious and I really don't want to hear it but, it does drive me crazy that she can do that and I'm unable (and maybe unwilling?) or maybe incapable of accomplishing this masterful management of fuel consumption.

Perplexed in Indy!

 

[EdP]

But, as we are cruising I-65 north on our return trip to Indy I have the cruise control locked at 75 mph and averaging 27.8 mpg. Not bad I think to myself. We stop for a fill up and change of driver and my wife averages 30.4 mpg the rest of the trip. She doesn't use cruise control because as she states, "I want control" of the speed, even though she is always surprised by how well the smart cruise control works when I'm using it. All the while she's cruising at a pretty good clip herself.
Perplexed in Indy!

Kudos to your wife, that is damned good.

I can think of a couple of things that may make a difference, but that is still a lot.

She is not travelling as fast, may 5 mph slower?

Unlike the SCC, she may be anticipating better and easing up on the gas sooner than the sensor would when traffic slows.
She may also be more gentle accelerating.

Some can also be terrain in the sections you each drove. You are gaining altitude on that route.

Next trip each drive opposite legs and see what happens.

 

[dougmcp]

If you wait 3 or 4 miles after you fill up and get back up to highway speed before you reset your fuel econ button you'll probably find your gas mileages are pretty similar.

 

[Mr. Incredible]

I have noticed in my 2018 G80 sport that I get significantly better MPG when I drive over allowing the cruise control to drive. I attribute this to two things,

AAC doesn't coast, it brakes
AAC hard accelerates after braking


The sonar cruise control doesn't coast, it brakes, it does well to pace the vehicle in front of you, but when I drive and the vehicle in front of me slows or someone changes lanes in front of me cutting the distance, I do not immediately hit the brakes, I take my foot off the throttle pedal and coast, braking only when needed, but the cruise does not, it brakes to slow the vehicle every time and sometimes pretty late and hard IMO, even with the ACC setting on 4-dots, it waits until it is at the end of that range then it brakes, which puts drag on the vehicle, it doesn't coast down, it brakes every time, and I experienced the same behavior in my last vehicle (Lexus) and in several rental vehicles I have had with ACC, and then when it has to re-accelerate to get back up to the set speed it does so by giving IMO too much throttle causing downshifting and harder acceleration, where I typically I don't have to accelerate that much because I was coasting, and if I do I feather the pedal and accelerate back up to speed slowly and purposely to keep the vehicle in it's top gear.


on my drive to work ~30 miles all highway, I have driven in control and I average 25-27mpg on the "current trip" stats, I have also used the adaptive cruise and it averages 18-19mpg, The on/off ramps are less than a mile from my house and office, so of a 32 mile trip 30 mile is all highway at highway speeds, 55-65mph as I go against the flow in rush hour, both ways.

 

[Starflyer]

I would like to see a "peanut" light in the heads up display when braking is applied. I normally set my cruise control to slightly less than most of the traffic so I don't get much automatic braking. When I do feel it, I normally click the "cruise" off as I prefer slowing down by wind drag rather than breaking.

I'm guessing auto braking cause extra tire wear and as well as brake pad wear. While I'm not sure, I get the feeling that adaptive cruise normally just eases up on the gas if the rate of closure is not great.

So if I saw a small peanut light when the brakes are applied I would click the cruise control off.

 

[Mr. Incredible]

I would like to see a "peanut" light in the heads up display when braking is applied. I normally set my cruise control to slightly less than most of the traffic so I don't get much automatic braking. When I do feel it, I normally click the "cruise" off as I prefer slowing down by wind drag rather than breaking.

I'm guessing auto braking cause extra tire wear and as well as brake pad wear. While I'm not sure, I get the feeling that adaptive cruise normally just eases up on the gas if the rate of closure is not great.

So if I saw a small peanut light when the brakes are applied I would click the cruise control off.

I've considered wiring one up myself.

 

[QuantumRift]

Yea the cruise control is great when there's not much traffic. On roads with moderate traffic it's frustrating to say the least.

I have noticed in my 2018 G80 sport that I get significantly better MPG when I drive over allowing the cruise control to drive. I attribute this to two things,

AAC doesn't coast, it brakes
AAC hard accelerates after braking


The sonar cruise control doesn't coast, it brakes, it does well to pace the vehicle in front of you, but when I drive and the vehicle in front of me slows or someone changes lanes in front of me cutting the distance, I do not immediately hit the brakes, I take my foot off the throttle pedal and coast, braking only when needed, but the cruise does not, it brakes to slow the vehicle every time and sometimes pretty late and hard IMO, even with the ACC setting on 4-dots, it waits until it is at the end of that range then it brakes, which puts drag on the vehicle, it doesn't coast down, it brakes every time, and I experienced the same behavior in my last vehicle (Lexus) and in several rental vehicles I have had with ACC, and then when it has to re-accelerate to get back up to the set speed it does so by giving IMO too much throttle causing downshifting and harder acceleration, where I typically I don't have to accelerate that much because I was coasting, and if I do I feather the pedal and accelerate back up to speed slowly and purposely to keep the vehicle in it's top gear.


on my drive to work ~30 miles all highway, I have driven in control and I average 25-27mpg on the "current trip" stats, I have also used the adaptive cruise and it averages 18-19mpg, The on/off ramps are less than a mile from my house and office, so of a 32 mile trip 30 mile is all highway at highway speeds, 55-65mph as I go against the flow in rush hour, both ways.

 

[TCM1974]

The quality of gas can make a difference. This was after about 20 mi @65mph after filling with non-ethanol premium.

 

[Starflyer]

The quality of gas can make a difference. This was after about 20 mi @65mph after filling with non-ethanol premium.

Is this mileage based on imperial gallons? Regardless, I wouldn't put much faith in a run of only 20 miles. Too many variables (speed, down hill, no stops, size of engine, etc, etc.

 

[QuantumRift]

E10 reduces your overall mileage 3-5% depending on the time of year. Remember, E10 involves replacing only 1/10 of your volume of fuel with ethanol, which has 75-80% btu content of gasoline. So if you have a 10 gallon tank (for example), and for example, the 100% gasoline you have in there has, again, for example, 114,000 BTU per gallon, for that 10 gallons you have 1,140,000 BTU available. Now remove ONE GALLON of that gasoline, and replace it with ONE GALLON of ethanol. By removing one gallon, you have 9 gallons of fuel, which now is 114,000 x 9 = 1,026,000 BTU. One gallon of ethanol, and we'll use 75% here, has 85,500 BTU. Add that gallon to the 9 gallons of fuel, and now your total BTU content for that E10 is now 1,026,000 + 85,500 = 1,111,500 BTUs.

Gas (10 gal) = 1,140,000 BTU
E10 (10 gall) = 1,111,500 BTU
--------------------------------------------
DIFF - 28,500 BTU for 10 gallons.

Now, if your engine was able to get, say 25 mpg with pure gasoline, you can expect E10 to give you somewhere around 97% of what you'd get with normal 100% gasoline. Less if weather is cold and fuel blends are changed for winter.

Of course, up to E85, you can expect a significant drop on fuel economy, and unless the E85 is much less than E10, it's not worth using it. You can expect as much as 25% less miles per gallon on fuel that's not much less per gallon than E10. If you CAN get E85 for 25% or more less than regular fuel, its a wash.

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[Starflyer]

E10 reduces your overall mileage 3-5% depending on the time of year.

Interesting about E10. Around my neck of the woods, there's almost no pure gasoline to be had. I do know of a farmer's coop that sells it, but the cost is certainly more that E10. I'm guessing it's a wash deal if it didn't involve extra driving to get to this station and worse, paying to drive there if it's not on my way.

 

[TCM1974]

Is this mileage based on imperial gallons? Regardless, I wouldn't put much faith in a run of only 20 miles. Too many variables (speed, down hill, no stops, size of engine, etc, etc.

With ethanol premium I usually get around 35-37mpg. I've observed different mileage from different stations using 93 octane premium and especially with 87 octane regular.

 

[Gunkk]

Well known that these engines (both GDI and port injected) have a well-tuned automatic advance/retard system for knock prevention. While I get about 10% better mileage with my car on 93 premium vs. 87 regular as a result, it's not enough to pay for the difference in price.

 

[Audio]

Well known that these engines (both GDI and port injected) have a well-tuned automatic advance/retard system for knock prevention. While I get about 10% better mileage with my car on 93 premium vs. 87 regular as a result, it's not enough to pay for the difference in price.

Didn't you say in one thread that you're a big V8 kind of guy, but now you're admitting to using gasoline that doesn't give your V8 it's full horsepower potential? Shame on you! lol

 

[Starflyer]

If we're talking about relitively new Genesises, 20-30 cents extra a gallon should be no big deal. 15,000 miles a year at 20 MPG comes out to 750 gallon yearly. Mulitipy that by 30 cents more and we're talking an exra $225 per year. Divide that by 12 and the extra charge for fuel is $18.75 monthly.

Peanuts with a $50K car. I'm probably getting closer to 22 MPG overall and nearly 30 MPG on the highway (I'm not burning the road up at 75-80 MPH). I've experimented with Super, Medium and Regular blends and I don't notice any difference in performance and have no idea if I get better mileage with Super or not, but for as much as $18.75 a month, I DON'T care. And actually I'm presently tracking more like 10,000 miles yearly.

Hey, if I was worried about the cost of fuel, I would be driving a Prius.

 

[Gunkk]

Didn't you say in one thread that you're a big V8 kind of guy, but now you're admitting to using gasoline that doesn't give your V8 it's full horsepower potential? Shame on you! lol

Yes I sure did. But my Genesis is my DD. Nice to have the extra torque from the 2 extra cylinders when merging or passing on the highway. Used to use more of the throttle a few years ago when I had the urge for some fun, but now it's not worth it to me in a 385 HP 4300lb car to pay an extra $16-18 per tank since I'm rarely matting the throttle anymore. Yes I'd rather keep from ragging out the car in spite of the HPP extended warranty. No 30% more fuel cost all the time is not worth 10% more performance occasionally.

Instead, I have this to go play with. Nearly double the power/torque as the 4.6 now satisfies my need for speed:


If I stick with the Genesis on my next DD (would be my 3rd Genny) I'll probably go for a 2016 v6 if I can get it in ultimate since a) the newer v6's have nearly the same power/torque as the 4.6, and b) I have a better car for fun.
So yes I'm guilty as charged. Sort of.

 

[BlancaGenny]

My wife and I own a home in Florida. We do the snowbird "thing" to rest and relax. Now granted, my wife's concept of "snowbird" is to go to Florida in the teeth of summer, but she explains that we, being a members of an aging populace, need to consider the length of days so we are not driving in the evening (all the while I'm thinking about the 99% humidity and how much the heat will make our visit slightly uncomfortable) since our eyesight presents challenges once the sun sets. Okay fine love!

But, as we are cruising I-65 north on our return trip to Indy I have the cruise control locked at 75 mph and averaging 27.8 mpg. Not bad I think to myself. We stop for a fill up and change of driver and my wife averages 30.4 mpg the rest of the trip. She doesn't use cruise control because as she states, "I want control" of the speed, even though she is always surprised by how well the smart cruise control works when I'm using it. All the while she's cruising at a pretty good clip herself.

Now the explanation is probably obvious and I really don't want to hear it but, it does drive me crazy that she can do that and I'm unable (and maybe unwilling?) or maybe incapable of accomplishing this masterful management of fuel consumption.

Perplexed in Indy!

Cruise control keeps the car as close to the set speed as possible. Whether it is braking, accelerating, or straight highway, the overall job is to keep that speed. I am hypermiling my buddy's C-Max while my car is in the shop and will do so in the rental I get later this week. It's a hybrid and I am at 273 miles at just under 1/2 tank (13.5 Gal). That puts me between 40-45 mpg at the moment. I'll have better numbers when I fill up. I'd love to see 500 miles on that tank before the fuel light comes on. Things I do:

-Anticipate red lights trying not to ever come to a complete stop.
-Never using cruise control
-Gradually gain speed before a hill and coast downhill
-Draft when I can and it's safe.
-Keep the tires about 4 PSI higher than advertised.

This is all very exhausting when I first started becoming a hypermiling junky. I started with a Saturn SL1 5 spd and was consistantly averaging 38 mpg. I honestly don't recommend it because it was indeed draining. Clarkson did it a decade ago with an Audi A8 diesel on an 800 mile loop in England. He didn't recommend it either. I enjoy is as I like to save money but it has been 4 years since I started so I'm use to it. Go ahead and try a couple times with what I do and there is also plenty of information on the web that is probably better than my techniques. As long as I see improvements, my goal is acheived. Have fun doing it

 

[QuantumRift]

As these engines are designed for 87 octane, there would be no obvious difference in MPG or performance between 87 and 91 and 93 octane. Unless the PREMIUM fuel was NON-ethanol, there would not be any difference (at least on a 6 cyl 3.8). I don't own an 8 cyl and therefore cannot speak as to the type of recommended fuel, but if the engine was designed for regular fuel, then the same results would be seen. Premium fuel (higher octane rating) has no effect on engine performance if used in an engine designed for 87 or 91 octane. It contains (depending on whether or not it is a top tier fuel) more and better cleaning agents for the valves and injectors, but with a GDI engine, any potential valve cleaning is negated by the GDI.


UPDATE: I just found this: for the 4.6 - "For improved vehicle performance, premium unleaded fuel with a Pump Octane
Rating of 91 (Research Octane Number 95) or higher is recommended."

So I stand corrected as I only have a 3.8 (97 octane), 93 will get you better performance, etc as the ECU isn't twiddling with the timing and so forth....but anything higher than 93, that wouldn't matter.

d

With ethanol premium I usually get around 35-37mpg. I've observed different mileage from different stations using 93 octane premium and especially with 87 octane regular.

 

[QuantumRift]

Yep, but I did choose the 6 cyl over the V8....

 

[Gunkk]

I get about 10% more fuel economy with 93 than with 87 in my car (both <=10% ethanol). However, it's not worth the ~$1/gal price difference (+30%) so I don't bother with 93.

Many local sources for 90 octane @0% ethanol locally for $4+/gal. Also not worth it.