$4+Gas Apparently doesn't bother everyone

[kinchy]

Had to drive to Philadelphia this past weekend. Took the 4Runner where I can (if all the stars are aligned correctly) average 23 MPG at 65-70MPH. When I tell you that at that speed in the center lane I was holding up traffic I'm not kidding. SUVs, large SUVs, full size V8's you name it are flying by in the left lane. I guess a certain segment of our population simply could care less. Maybe if I were in a 911 Turbo I would be in the left lane as well.

[Dave McReynolds]

I notice the same thing on CA highways. There are a minority of folks apparently trying to keep it to 60 mph or so, whereas a majority seem to be business as usual. I do notice editorials popping up fairly regularly now saying that we need a lower national speed limit, so you may have fewer people flying by you soon.

[Quinn]

Are cars still optimized for 55mph?

Wonder what speed RTs are optimized at. I usually cruise at 75 and slip up to 80 for the engine not to bog down in 6th gear going up hill.

 

 

[motoguy128]

Are cars still optimized for 55mph?

Wonder what speed RTs are optimized at. I usually cruise at 75 and slip up to 80 for the engine not to bog down in 6th gear going up hill.

 

 

Speeding up going up hill to increase the RPM's might improve your effeciency, but it definitely won't help your economy. Almost all IC engines make peak effeciency around 50-55mph, but thet effeciency, if very aerodynamic, will continue up to 65mph. The RT, isn't the most smooth at 55mph in 6th gear, but the laws of physics still apply, so it will make the best economy there. But it will be about hte same at 60mph. Anything above 60 and economy will start to trail off. But I suppose... YMMV.

 

As another post a while back mentioned, you should also consider the cost of your time. If you only have 3 weeks of vacation, your vacaton time might be worth $30/hour or more. So spending $10 extra to save 1 hour, is good economics. However, if you're retired, the value or your time is only dependent on how much longer you think you'll live. That's hard to place a price on.

[Marty Hill]

 

 

 

However, if you're retired, the value or your time is only dependent on how much longer you think you'll live. That's hard to place a price on.

 

Having noted you thoughts, I say...ride on and don't worry, be happy!!!

[4wheeldog]

I road 307 miles yesterday and put 5.8 gallons in the tank when I was done. I spent some time between 60 and 70, but the majority of those miles were at 80 to 85. There is something to be said for smootheness.........And also for living at high elevation.

[Bob Palin]

Almost all IC engines make peak effeciency around 50-55mph

What a peculiar thing to say! I'm betting the IC engine in the average Cessna or 18 wheeler or lawn mower isn't at its most efficient at 55mph.

[smiller]

Almost all IC engines make peak effeciency around 50-55mph

What a peculiar thing to say! I'm betting the IC engine in the average Cessna or 18 wheeler or lawn mower isn't at its most efficient at 55mph.

It's all in The Gospel According to Joan Claybrook.

[Joe Frickin' Friday]

Almost all IC engines make peak effeciency around 50-55mph...

 

As Killer notes, a strange thing to say. The thermodynamic efficiency (crankshaft power divided by fuel flow rate) of an engine is a function of its own RPM and load, which may or may be directly related to a vehicle's forward speed (assuming said engine is in fact powering said vehicle's forward motion).

 

If you put your pedal to the floor, the engine itself is in fact operating fairly close to its peak efficiency; spark-ignited gasoline engines obtain their best efficiency at middling RPM and high load, and that efficiency drops off only a bit as the RPM's go up from there. However, as the load drops (as you ease up on the gas), the efficiency drops pretty quickly.

 

At 130 MPH, the engine in your mid-size sedan is operating quite efficiently, but the vehicle's power requirement is very large. Net result, fairly crappy MPG.

 

At 75 MPH, the engine is operating with "decent" efficiency, and the vehicle's power requirement is more modest. Net result, reasonably good fuel economy.

 

At 55 MPH, the engine is operating at a small fraction of peak load and delivers pretty bad efficiency, but the vehicle's power requirement is quite low. Net result, very good fuel economy.

 

At 25 MPH the engine is hardly exerting any torque at all, but is delivering single-digit efficiency. Vehicle power requirement is berry berry small, but that rotten engine efficiency means your MPG is starting to go down again.

 

Peak MPG may or may not be at 55 MPH; it depends on the engine, the vehicle, and the gearing. Cars aren't particularly "optimized" for 55 or 75 or any other speed, it just happens that the combination of the engine's efficiency curve with the vehicle's speed-versus-s power curve generally results in best MPG somewhere between 40 and 65 MPH.

 

Diesel engines have a much flatter efficiency curve with respect to load; the result is that diesel-powered vehicles are likely to see a much more substantial improvement in fuel economy from reducing their cruise speed.

[smiller]

Diesel engines have a much flatter efficiency curve with respect to load; the result is that diesel-powered vehicles are likely to see a much more substantial improvement in fuel economy from reducing their cruise speed.

And so they do... dammit... (says the owner of a diesel truck.)

 

[Quinn]

I guess I assume that new car's transmissions and torque curves are designed to give the best results on the EPA dynamos so they can brag about their highway mileage on the stickers. I remember reading somewhere that aerodynamic styling is factored in using fomulas instead of real world driving. Because motorcycles don't have a sticker showing highway and city (or is it combined now) mileage, they don't have the constraint of 50 or 55 mph. Sixth gear on an RT is definetly not designed for that low a speed and puts a strain on the motor. So, I was wondering where the sweet spot for a BMW was. I'm guessing around 75 or 80.

 

 

[smiller]

So, I was wondering where the sweet spot for a BMW was. I'm guessing around 75 or 80.

Which 'sweet spot' are you looking for? Most efficient in terms of energy output per unit of fuel consumption? Probably WOT. Lowest fuel consumption without regard to efficiency? Probably a very slow speed. Everywhere in between is a compromise. But 70-80 mph is a popular choice because that's around the point where air resistance starts to become a very large factor, and as a result higher speeds will use disproportionately more fuel. In reality the engine is probably operating more efficiently at high speeds, but the energy being generated is more and more being used to overcome wind resistance than it is to increase speed, so from the rider's perspective the extra energy is going towards a less desirable use.

 

[Quinn]

Personal rant:

 

A couple of the local TV stations have had news features about how more people are running out of gas and requiring rescue from the side of the road. Makes you wonder how they'd deal with a leaky radiator, flat tire, or inspection sticker due if they can't find a five dollar bill to get enough gas to get them all the way to work. Maybe if they were making payments on an $8k car instead of a $30k one, they'd stand a better chance. Gas just isn't the most expensive thing about owning a vehicle.

 

 

[YesMan]

All I can say is, in overall driving, my pickup averages 16mpg doing freeway speeds of 65 or 75. Doesnt seem to make a difference??

 

But the RT makes up for it, currently averaging about 52-53 mpg. The latest tank was all freeway, mostly at 80mph (stock windshield down, as this seems to dent the milage, slightly).

[YesMan]

What I find amazing, is a story on the radio last week. A local station was selling gas at 3.99/g.

 

There were people waiting up to an hour, to get the gas.

 

It seems like the average in that area is about mid 4.40's (If you look around you can get $4.29). So at $.45/g, most tanks hold 15-25g, if the tank was completely empty, they would be benefit about $10?? Not even figuring the gas wasted starting/stoping the vehicle, in line, or going out of your way to go to that station.

 

They interviewed one lady, and she only needed 1/2 a tank!

 

Doesn't seem worth it to me.

[grizzly660fan]

in my diesel truck with manual transmission, my best fuel economy is if I can keep the RPM's around 1900 and my turbo boost gauge at 10lbs or less of boost. In sixth gear on flat that is about 70mph. in 5th gear that is 58mph'sh. empty or not towing I can avg 20mpg if I follow those rules. If I step outside those numbers the mpg drops off fairly quickly.

 

the main question was does $4 gallon affect anyone, the answer for my family is YES! I started cutting back our extra trips and doing what I could to lower our fuel consumption about two years ago, there isn't much more I can do to lean it out again, so this means fewer places to go, cutting back in other areas, etc.

 

 

[Joe Frickin' Friday]

the main question was does $4 gallon affect anyone, the answer for my family is YES! I started cutting back our extra trips and doing what I could to lower our fuel consumption about two years ago, there isn't much more I can do to lean it out again, so this means fewer places to go, cutting back in other areas, etc.

 

If that was the question, the answer for me is no. As I mentioned in an earlier post, the money saved versus the time spent works out to somewhere in the neighborhood of $3-$4 per hour, considerably less than minimum wage. If someone told you "sit in this comfortable chair for an hour, and we'll give you $3," would you do it? Maybe, if you really had nothing much else going on in your life. But my life is not that empty - I have things I want to do with my time, and puttering along in a car, even if comfortable, isn't on that list - and I'm not that short of cash.

 

I still take pleasure cruises on the bike, using premium fuel and gleefully engaging in wasteful throttle management practices (jackrabbit acceleration, heavy braking). On the highway, car or bike, I'm sticking with a smidge above the speed limit; here in Michigan, that means I'm typically doing about 75 MPH.

 

Apart from combining errands, the one other thing I do is try to wait until I'm on the south side of town (while on one of those combined errand trips) to buy gas; it's typically cheaper there by ten cents a gallon.

[Bob Palin]

If that was the question the answer for me is, definitely. At $2 a gallon (which it was when I bought my truck) I thought nothing of going over to Richfield to buy things, I didn't go every week but when I needed something I couldn't get locally I went. Now I hardly ever go over there, it's cheaper to buy things on the net, even small things. I don't take my truck out as much to go exploring either, in fact it hasn't been off road since spring Torrey. I wouldn't have bought a 15 mpg truck had I known the price of gas was going to double.

[Joe Frickin' Friday]

If that was the question the answer for me is, definitely. At $2 a gallon (which it was when I bought my truck) I thought nothing of going over to Richfield to buy things, I didn't go every week but when I needed something I couldn't get locally I went. Now I hardly ever go over there, it's cheaper to buy things on the net, even small things. I don't take my truck out as much to go exploring either, in fact it hasn't been off road since spring Torrey. I wouldn't have bought a 15 mpg truck had I known the price of gas was going to double.

 

Interesting to note that while people are obsessing over the cost of gas, that's typically only a modest portion of the overall per-mile operating cost of a vehicle. Unless one buys a very used vehicle at a fraction of the new price, depreciation costs are huge. Throw in tires, oil, insurance, and maintenance, and total operating costs per mile get to be quite large. For my Maxima, it's about 44 cents per mile, of which the fuel accounts for only 13 cents. Note too that that cost is averaged over the life of the vehicle; with 60K miles and six years on it, it's depreciating rather slowly now, so the per mile cost at this time is probably a lot less (and probably used to be a lot more).

 

I'll note that the IRS allows business mileage to be itemized at 58 cents per mile. This includes a recent increase of 8 cents due to rising fuel prices. IOW, the IRS agrees that fuel is not your only operating expense; moreover, they feel that average per-mile total operating cost has only increased by about 16 percent recently.

 

Your truck's fuel cost is closer to 27 cents per mile, which is indeed getting up there, but have you thought about all those other expenses? Your fuel cost may have gone up by 100 percent, but I'll bet your total per-mile operating cost has increased by a much smaller fraction.

[Quinn]

I don't think that paying $4.00 for gas bothers me as much as paying $4.10 at this station and seeing it for $3.86 twenty miles down the road at another. I just hate to reward the obvious avarice of oil companies and will go miles out of my way for a cheaper price (sometimes even when it's past the break-even point).

 

 

 

 

[Matts_12GS]

I don't think that paying $4.00 for gas bothers me as much as paying $4.10 at this station and seeing it for $3.86 twenty miles down the road at another. I just hate to reward the obvious avarice of oil companies and will go miles out of my way for a cheaper price (sometimes even when it's past the break-even point).

 

Obviously it's all the oil company's fault...

 

I'd bet you a lot of those stations are NOT company stores, but independent operators.

 

They will charge in effect what the local market will bear. Convenience costs more...

 

I live in a yuppie haven and so gas is a dime a gallon more than near where I work downtown. So, that dime a gallon costs me $.60 per fill up without having to go 40 miles out of my way. I like to ride, but have more important things to do than try to "stick it to the man."

[Bob Palin]

Interesting to note that while people are obsessing over the cost of gas, that's typically only a modest portion of the overall per-mile operating cost of a vehicle.

Absolutely, but those other costs have remained pretty much the same where the cost of fuel has doubled and that doubling is reflected directly in the number of miles driven. I can't do anything now about the depreciation of my truck or much about the cost of insurance and registration, I can affect the number of miles I drive.

[velomoto]

Interesting to note that while people are obsessing over the cost of gas, that's typically only a modest portion of the overall per-mile operating cost of a vehicle.

+1

 

I figure using my 12RT is costing about $0.07 per mile for tires and $0.08 per mile for gasoline. Factor in the cost for insurance, license, maintenance and gas is but a small portion of the operating cost. Sure it was nicer when fuel was half that, but in the larger picture the difference is negligible.

 

If however one changes the picture to that of the typical teenager or self-supported college student, then the difference in the cost of gas will have a huge impact on their personal finances.

 

FWIW, I've seen reports indicating the 12RT has significantly better economy at 60 to 65 mph than at 75 mph (around 10 mpg or 20% more if I remember correctly).

[Albert]

Almost all IC engines make peak effeciency around 50-55mph

What a peculiar thing to say! I'm betting the IC engine in the average Cessna or 18 wheeler or lawn mower isn't at its most efficient at 55mph.

 

Imagine the lowly stationary generator.

[Bob Palin]

Sure it was nicer when fuel was half that, but in the larger picture the difference is negligible.

When it is 16 miles to the nearest grocery store and 66 miles to the nearest town with anything more than that the difference is not negligable.

 

Please note I am not complaining, I like living here and there is a price to be paid, but that doesn't mean I don't notice it and am not affected by it.

[Marty Hill]

Just ordered a new Jetta TDI. Wow, only a 39 year break even on the fuel savings. Let's see, how old will I be then?

 

[Mister Tee]

Almost all IC engines make peak effeciency around 50-55mph

What a peculiar thing to say! I'm betting the IC engine in the average Cessna or 18 wheeler or lawn mower isn't at its most efficient at 55mph.

 

Cessna:

 

A 172 is most efficient at 60 knots (about 70 mph) which is its best glide speed, where the sum of induced and parasitic drag is lowest. This is the speed at which you would fly if you lost the engine, or you were critically low on gas. Engine itself is running most efficiently at about 130 knots, which is its top speed.

 

18 Wheeler:

 

Tough one. True efficiency is a function of load vs. fuel consumption. A fully loaded triple tandem driven at moderate speeds would be most efficient. Minimizes frontal drag in relation to transported weight. The aerodynamics for trucks are lousy, but they beat a Prius when comparing weight to drag. Most efficient speed is probably around 40-50 mph, but that's just a guess. Engine is probably running most efficiently at that speed as well, depending on the load and gearing.

 

Lawn Mower:

 

Most efficient speed, generally, is as fast as you can push it. If you could mow your lawn at 55 mph without stalling the motor, the mowers engine would be most efficient at 55 mph.

[Matts_12GS]

Dibs on Marty's jetta when he's ready to move on!

 

[SeanC]

Lawn Mower:

 

Most efficient speed, generally, is as fast as you can push it. If you could mow your lawn at 55 mph without stalling the motor, the mowers engine would be most efficient at 55 mph.

Dunno 'bout efficiency, but my lawn mower will definitely be most economical when my (currently 3yo) son is old enough to push it.

[Joe Frickin' Friday]

Dunno 'bout efficiency, but my lawn mower will definitely be most economical when my (currently 3yo) son is old enough to push it.

 

Sure, if you can get the neighbors to feed him. If not, it'll show up in your burgeoning grocery bill...

[Marty Hill]

 

 

Cessna:

 

A 172 is most efficient at 60 knots (about 70 mph) which is its best glide speed, where the sum of induced and parasitic drag is lowest. This is the speed at which you would fly if you lost the engine, or you were critically low on gas.

 

Bes GLIDE speed would be about 60 kts.

Doubt the 60kts if low fuel. Bad angle of attack/wasteful. 85-100 kts leaned to the limit would be more efficient and safer.

[Mister Tee]

 

Cessna:

 

A 172 is most efficient at 60 knots (about 70 mph) which is its best glide speed, where the sum of induced and parasitic drag is lowest. This is the speed at which you would fly if you lost the engine, or you were critically low on gas.

 

Bes GLIDE speed would be about 60 kts.

Doubt the 60kts if low fuel. Bad angle of attack/wasteful. 85-100 kts leaned to the limit would be more efficient and safer.

 

I agree probably safer, but not more efficient. Flying at best glide speed will yield the lowest power requirement - however, if you want to get technical, the most efficient way to gain range is do a series of full power climbs at Vy, followed by idle decents at best glide speed.

[David]

You're confusing efficiency with power and efficiency without it. You're also confusing horizontal efficiency (what we're talking about) and vertical efficiency (best glide).

[Couchrocket]

That was my first thought, too... that there must have been a whole bunch of slack in the "average" American's budget that allows "business as usual" at the gas pump, while perhaps trimming back in other discretionary places.

 

My wife and I had been talking about this, since we've been more careful about vehicle use.

 

Then just this morning I was in conversation with a local water district here in the greater Southern CA area (a client).... and was absolutely flabbergasted to learn two things from them: In the past year their "no pay" rate has jumped to 30% of their residential customers! And, they've had theft of wiring to their facilities (much of the time while it is "hot" and in service -- scrap copper is a target of choice here) of $500,000.00 in the last 6 months!

 

I've been wondering if people were just living on credit more and more to offset the fuel costs... a full 1/3 of the residential population not being able (or willing) to pay their water bills is stunning, I think, and may be very telling of what is to come in fairly short order when it is time to pay the piper.

 

Don't know what to make of the theft rate. There are always thieves out there plying their trade, but apparently this increase in theft (by non-employees) is orders of magnitude above the norm for these folk.

 

This made me wonder about "what else" is going on out there that is currently below the media radar, but that could be a harbinger of bad things to come.

[David]

Scott, I think you're right. The next financial crisis will be two-fold--instead of making adjustments in standard of living, many folks seem to be closing that gap with a combination of revolving consumer debt and loans against retirement accounts.

 

The folks in the UK are already in deep trouble with the former, and that's not good for yet another of the world's largest economy.

[smiller]

I'm frankly a little insulted. My Lincoln Navigator doesn't run on air. And big-screen TVs don't grow on trees, and Blu-Ray is coming out. I have to rob my retirement account because I have to make ends meet somehow you know... I really don't think you've thought this through...

 

[David]

Hey, you're not replacement for Greg. It'll take more than "no smileys" to get me going.

[smiller]

You got me, I'm really going to wait a year on the Blu-Ray.

 

Seriously, I'm not worried about '$200/barrel' oil or the collapse of the banking system, but the fact that we've run the consumer economy on credit for the past decade or two does have me concerned. I'm really not anxious to see the second shoe drop there...

 

[DiggerJim]

Just ordered a new Jetta TDI. Wow, only a 39 year break even on the fuel savings. Let's see, how old will I be then?

I had one - never reached break-even despite doing 45,000 miles/yr. The thing cost me an extra 5K in maintenance over 3 yrs. Figured I had to do another 160K trouble & maintenance free miles to break even so I dumped it, got a Saab 9-3 that's getting an honest 29.5mpg and have smiled everytime I see that diesel costs way more than the regular I'm putting in the car.

[Kitsap]

As a side...

 

The family and I picked up our Ford Mondeo TDI in Copenhagen yesterday and did mostly 120 kph to Billund averaging 31mpg per the on board computer. I used to hate deisels but would change my mind if Ford brought this thing back to the states. Also to my surprise diesel is cheeper than standard fuel here.

 

..The bakeries are cutting in the fuel consumption..

[russell_bynum]

As a side...

 

The family and I picked up our Ford Mondeo TDI in Copenhagen yesterday and did mostly 120 kph to Billund averaging 31mpg per the on board computer. I used to hate deisels but would change my mind if Ford brought this thing back to the states. Also to my surprise diesel is cheeper than standard fuel here.

 

..The bakeries are cutting in the fuel consumption..

 

I'm suprised your mpg was that low. I get low 20's in my bigass 4x4 pickup. I would expect a passenger car to do much better. Some of the TDI Jetta guys I've talked to say 48-50 isn't uncommon.

 

By everything I've seen, diesel should be cheaper than gasoline. When I bought the truck 4 years ago, diesel was about $0.30/gal cheaper than regular unleaded.

[Boffin]

My Isuzu engined Vauxhall (UK name for Opel, owned by GM) Vectra 2.0 diesel gets 36mpg(US) in mixed traffic (like that Copenhagen to Billund run) and 40mpg on a long steady cruise at 70mph. Drop the speed to 55mph cruising and I get over 50mpg and fall to sleep.

 

Andy

[Mister Tee]

You're confusing efficiency with power and efficiency without it. You're also confusing horizontal efficiency (what we're talking about) and vertical efficiency (best glide).

 

Not really. My claim is that procedure will get you the furthest horizontal distance on a given volume of gas.

[Marty Hill]

Let us know how it works out on your next x-country.

[David]

I'm going to go buy another shovel for you--when you wear that one out, just yell and I'll throw it down the hole to you.

[Mister Tee]

Let us know how it works out on your next x-country.

 

Okay, we'll put this one to rest with a thought exercise. For some odd reason, I just happen to have a 172R POH lying around, so, from numbers taken from the manual:

 

Scenario 1: Climb and coast

 

For a full load climbout at 2450 pounds to 10,000 feet, fuel burn is 4.0 gallons, and the horizontal distance traveled is 29 NM. Assuming an optimistic glide ratio of 12:1, one travels an additional 20 NM for a total length of 49 NM. Assuming you cut the throttle at 10,000 feet, fuel burn is still 4 gallons and the mileage is 12.3 NM/g for the segment.

 

Scenario 2: Economy cruise

 

Level at 4,000 feet, minimum operating cruise RPM (1900 RPM/50% power), speed is 90 KTAS and fuel burn is 5.8 gph. Mileage is then 15.5 NN/g. That's leaned as recommended - leaned for best economy (at peak EGT) fuel burn would be a bit less.

 

Marty wins. The problem here is that although, theoretically, the engine should operate at peak efficiency at full power during climbout, in practicality, one has to climb at a full rich mixture, which really whacks economy on that segment of the trip. I don't have numbers for a lean-of-peak climbout, which is what I routinely do in the Bonanza I fly. Maybe the next time I fly it I'll try that a couple times to see what happens.

[Boffin]

Ah, Mr Tee, you are confusing efficiency with economy. Peak efficiency means the engine is at the point where it is best at turning chemical energy into mechanical energy - getting the most power out of the fuel. That can and does happen when the fuel is being poured in at a vast rate. The engine may be getting 40% of the energy out but burning lots of fuel. Peak economy occurs where the efficiency curve crosses the required power curve. The power needed to climb - or travel at max V on a bike - is much higher than that needed to cruise, so the engine can turn fuel into power with less efficiency and less burn.

 

Andy

 

[Marty Hill]

I've got 873 hours in an F-33A. I sure as hell would not fly it that way. Enjoy the ride and remember to retract the gear...it will help.

[Mister Tee]

Ah, Mr Tee, you are confusing efficiency with economy. Peak efficiency means the engine is at the point where it is best at turning chemical energy into mechanical energy - getting the most power out of the fuel. That can and does happen when the fuel is being poured in at a vast rate. The engine may be getting 40% of the energy out but burning lots of fuel. Peak economy occurs where the efficiency curve crosses the required power curve. The power needed to climb - or travel at max V on a bike - is much higher than that needed to cruise, so the engine can turn fuel into power with less efficiency and less burn.

 

Andy

 

I understand that - one of the reasons that hybrid cars get better mileage ("economy") than standard cars, at least at low speeds, is that their engines are able to run for short durations at a higher, more efficient power level, vs a long duration at a lower, less efficient power level. That is the theory behind the "glide and coast" scenario.

[Mister Tee]

I've got 873 hours in an F-33A. I sure as hell would not fly it that way. Enjoy the ride and remember to retract the gear...it will help.

 

I wouldn't ACTUALLY cut the engine in an A36 and let it glide to the ground.