Disputing gas saving tips

Now that gas prices are so high I've been hearing a lot of gas saving tips from "The experts" on the news and in newspapers and magazines. Most of them make sense like accelerating slowly, keeping your engine tuned and your tires inflated properly. The one that gets me, and keeps coming up is the one that says to shut the engine off if idling for more than a minute. Now I am by no means an "Expert" but I dispute this claim. I understand that less running time = less gas being used, but what about switching from closed loop back to open loop and the engine revving up for startup? And they say you should not warm up the engine before driving. My opinion is that not warming up an engine will waste more gas due to compression not being what it is when warm, and running the engine under more of a load and more rpm's in open loop. My question is: Does anyone have any facts to dispute this or prove this? Opinions are also appreciated. Sorry for the long post.

my father was an engineer and he decided to sit me down and describe the formulas for this type of stuff, pollution aside, on the average car to make it worthwhile to shut it down you would have to be idling for 4 mins or more to save gas

just his .02

Long post, give me a break, I have never written a post that short in my life, LOL.
:laugh:

Newer cars are designed to switch into closed loop operation in less than a minute of start up. Warm up time to reach closed loop varies with some of us, based on mods, climate, age of the system and condition of the vehicle. I would not shut off the engine unless it will be off for at least 5 to 10 minutes. A hot engine will not need a warm up to go back to closed loop operation. The secret to rapid shifts to closed loop operation is the HEGO oxygen sensors that have an internal electric heater that heats up the active sensor element in seconds.

There are some here that claim that one should allow engine coolant to warm up to maybe 160 F in cold climates before driving to save gas, which may be partly true, but I have seen no hard data on this.

88 Wagonman said:

Now that gas prices are so high I've been hearing a lot of gas saving tips from "The experts" on the news and in newspapers and magazines. Most of them make sense like accelerating slowly, keeping your engine tuned and your tires inflated properly. The one that gets me, and keeps coming up is the one that says to shut the engine off if idling for more than a minute. Now I am by no means an "Expert" but I dispute this claim. I understand that less running time = less gas being used, but what about switching from closed loop back to open loop and the engine revving up for startup? And they say you should not warm up the engine before driving. My opinion is that not warming up an engine will waste more gas due to compression not being what it is when warm, and running the engine under more of a load and more rpm's in open loop. My question is: Does anyone have any facts to dispute this or prove this? Opinions are also appreciated. Sorry for the long post.

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Your engine will not likely cool off enough to go back into open loop mode if it's just a few minutes. If it's that cold out, you'll need the engine running for the heater.

Use gas that doesn't contain ethanol. An XJ with a 4.0 looses approx. 4 mpg when the gas contains 10% ethanol.
If in doubt, ask the gas company, I did and they told me.
Fortunately there are a few gas stations in town that still sell real gas.
Real gas provides better performance and mileage and doesn't hurt the environment like ethanol does.

I tend not to extend my warm up times. I start it up, wait for the guages to go normal, back out, get out and close the garage door, and I'm gone.

As for wasting fuel idling, I usually look at it as "Extended time idlng". So when I'm wheeling, I shut it off when I'm watching folks doing an obstical. If I'm waiting at a train crossing, and I got there when the gate closed, I'll stut it down. At traffic lights, it stays running. It takes a few minutes when the weather is warm for the O2 sensors to cool enough to do the whole open>closed loop thing. There is not a large enough difference between the open loop map and the closed loop learned values to make a huge difference in fuel economy for the period of time the engine is between states.

As to the 10% ethanol claim of a drop of 4 mpg, I don't agree. I have seen no difference between 10% ethanol blend and 87 straight up.

Ron

Fuel saving tips?

Cruise (steady-state) at or near the torque peak of your engine. RENIX cruises best at 2800-3000rpm, HO slightly higher (say, 3000-3200rpm.) If this means not using overdrive, don't use overdrive. It will help.

Accelerate slowly and smoothly - don't just stick your foot in it all the time. If other drivers get hacked off at you, that's their problem. They should have left the house earlier.

Allow some following distance - give yourself time to react smoothly and easily. Remember: every time you have to slow down, you'll have to speed up again...

Keep your tyres inflated properly - use chalk to find the right pressure if you have to (put chalk marks across the treads, drive a few feet, and check. You should wear it all off evenly - if the centre wears first, let a couple pounds out. If the edges wear off first, add a couple pounds. Load the rig as you do in day-to-day driving. Remember: if you change your brand/model of tyres, recheck your inflation pressure. Ditto if you change your basic load.)

Keep your engine in tune - cap & rotor and spark plugs are a huge factor here.

These things are a bit older. Keep the fuel system clean. Regardless of whether acetone works to cause more efficient combustion, add about four ounces to the tankful (about an ounce every four gallons.) Acetone is already added to gasoline as a cleaning agent - you're just increasing the concentration slightly. Acetone is an oxygenated hydrocarbon (itself a fuel,) and will burn cleanly on its own.

Most of what you can do to save fuel is actually monitoring your driving habits, and changing them where necessary. Don't get in a huge hurry - you'll waste fuel (and time.) That's probably the single biggest thing you can do to save fuel.

"Driving the speed limit" doesn't automatically save fuel - most vehicles aren't properly geared/tyred for it. It should be close, but it won't be spot on. If you have to go a little faster, move to the left and do so. If you have to go a little slower, move to the right and do so. While the national 55mph speed limit was supposedly passed to save fuel, it does a damn poor job of doing so (most manufacturers gear their vehicles to turn the crank slowly at cruising speed - you may as well be lugging the engine...)

@falcon556 - are you saying that EtOH harms the environment on its own (it should not - it's also an oxygenated hydrocarbon, and burns very cleanly like most alcohols) or that it harms the environment by increasing fuel consumption (which makes sense, as the energy content of EtOH is lower than gasoline?) Please be clear - if you've got an incorrect premise (or I do!) I'd like to make sure whichever one of us gets corrected so we're all on the same page. I'm not saying "I'm right and you're wrong" (it could be quite the opposite,) but I'd like to make sure we're both thinking the same thing.

5-90 said:

@falcon556 - are you saying that EtOH harms the environment on its own (it should not - it's also an oxygenated hydrocarbon, and burns very cleanly like most alcohols) or that it harms the environment by increasing fuel consumption (which makes sense, as the energy content of EtOH is lower than gasoline?) Please be clear - if you've got an incorrect premise (or I do!) I'd like to make sure whichever one of us gets corrected so we're all on the same page. I'm not saying "I'm right and you're wrong" (it could be quite the opposite,) but I'd like to make sure we're both thinking the same thing.

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At first they were pushing ethanol as a green fuel, the government threw billions of your money in the production and like they said in USATODAY (I think), no candidate dared to go to Iowa and not say "I love ethanol".
Later studies showed that if you consider the entire process of planting, fertilizing, producing transporting, using it and getting less mpgs, the total result makes it worse than oil. I believe that is the reason that most politicians now claim that we need it for energy independence, which of course is pure BS because no matter how much we plant it can never be more than 10% of our consumption. It also brings food prices up. In the mean time we refuse to drill in Alaska, East Coast, West Coast etc, making our entire nation hostage to some of the most disgusting regimes in the world.
MPG does go down. Last summer I decided to find out for my self whether there is a difference in mpg between 2Hi and 4FT. I kept records of every single refill. At the end of the summer all of a sudden my mpg dropped and the transmission would downshift sooner than normal when accelerating. It took me months to figure it out, just about the time I was thinking about replacing the O2 sensor, I read how a neighboring state went to E10. That prompted me to call the gas companies and I was told that I was getting E10.
I found a few Phillips 66 stations that still sell real gas and guess what, my mileage and power came back.
I didn't replace the O2.

BTW friends and family that checked their mileage and switched, agree with the obvious, mpg went up with real gas.

falcon556 said:

At first they were pushing ethanol as a green fuel, the government threw billions of your money in the production and like they said in USATODAY (I think), no candidate dared to go to Iowa and not say "I love ethanol".
Later studies showed that if you consider the entire process of planting, fertilizing, producing transporting, using it and getting less mpgs, the total result makes it worse than oil. I believe that is the reason that most politicians now claim that we need it for energy independence, which of course is pure BS because no matter how much we plant it can never be more than 10% of our consumption. It also brings food prices up. In the mean time we refuse to drill in Alaska, East Coast, West Coast etc, making our entire nation hostage to some of the most disgusting regimes in the world.
MPG does go down. Last summer I decided to find out for my self whether there is a difference in mpg between 2Hi and 4FT. I kept records of every single refill. At the end of the summer all of a sudden my mpg dropped and the transmission would downshift sooner than normal when accelerating. It took me months to figure it out, just about the time I was thinking about replacing the O2 sensor, I read how a neighboring state went to E10. That prompted me to call the gas companies and I was told that I was getting E10.
I found a few Phillips 66 stations that still sell real gas and guess what, my mileage and power came back.
I didn't replace the O2.

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OK - so you're not thinking that the EtOH itself isn't burning cleanly, but that the "carbon footprint" of manufacture and distribution offsets the savings in the "carbon footprint" of burning the stuff in the first place, right?

Mainly, I just wanted to make sure that's what you were thinking. As I said earlier, EtOH does burn cleanly (as well as MeOH and other alcohols,) but it does take rather more energy to manufacture the stuff than you gain by burning it, so it's actually an "energy-negative" fuel by the time you're all done. That is the issue with EtOH (and MeOH, for that matter) - it's not burning the stuff that's the problem, it's making it in the first place. (MeOH is A/K/A "wood alcohol," and can be made from cellulose, vice sugar for EtOH. We can make MeOH from waste matter - like corn plants, rather than corn proper, but it's still going to be energy deficient...)

5-90 said:

OK - so you're not thinking that the EtOH itself isn't burning cleanly, but that the "carbon footprint" of manufacture and distribution offsets the savings in the "carbon footprint" of burning the stuff in the first place, right?

Mainly, I just wanted to make sure that's what you were thinking. As I said earlier, EtOH does burn cleanly (as well as MeOH and other alcohols,) but it does take rather more energy to manufacture the stuff than you gain by burning it, so it's actually an "energy-negative" fuel by the time you're all done. That is the issue with EtOH (and MeOH, for that matter) - it's not burning the stuff that's the problem, it's making it in the first place. (MeOH is A/K/A "wood alcohol," and can be made from cellulose, vice sugar for EtOH. We can make MeOH from waste matter - like corn plants, rather than corn proper, but it's still going to be energy deficient...)

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Yep, that's the story.

Keep in mind a full tank of gas weighs about 125lbs. So I chose to put in only a 1/4 of a tank at a time. That's at least almost a 94lb difference which helps a little. Plus, since you fill up so often, you realize how much you spend in gas which makes ya not want to drive lol. Works for me anyways Oh, also, running full synthetic everything helps a lot too.

PurpleCherokee said:

Keep in mind a full tank of gas weighs about 125lbs. So I chose to put in only a 1/4 of a tank at a time. That's at least almost a 94lb difference which helps a little. Plus, since you fill up so often, you realize how much you spend in gas which makes ya not want to drive lol. Works for me anyways Oh, also, running full synthetic everything helps a lot too.

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Full synthetic I'll agree with - but I'll dispute the other one. How much fuel are you saving if you're running back and forth to the filling station all the time? With the average commute (at least out here...) just carrying the extra hundred pounds or so in fuel isn't that big of a problem, compared to the hassle of running about (saving time can also be saving money, in most cases. How much can you get done if you're doing the stuff you think is necessary?)

If you've got a short commute - or only run errands - that's not a huge problem. If you've got a bit of a drive in front of you, I don't think that's a very good idea.

One thing we've done is we're down to one operating vehicle (my 88 needs work anyhow, so I've downchecked it for the time being and got "comp only" coverage on it.) I don't run about much and I work from home. Most of the running about I do is taking her mother to various medical appointments and such, but we still only tank up about twice a month.

Now, if I could cut the five or six medical appointments a month out of my running about, I'd be happy. I've still got a few PT appointments for myself (still recovering from my broken neck,) but that's only one a week for the next month or so - I do as much as possible at home. Apart from that, if I do have to run about, I try to do as much as possible outside of the "business day" (read: Hellish traffic...) which also saves fuel. Remember how I said driving habits are probably the biggest thing you can do to save fuel? There you go - plan accordingly.

Keep in mind a full tank of gas weighs about 125lbs. So I chose to put in only a 1/4 of a tank at a time. That's at least almost a 94lb difference which helps a little. Plus, since you fill up so often, you realize how much you spend in gas which makes ya not want to drive lol. Works for me anyways Oh, also, running full synthetic everything helps a lot too.

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I have also heard that there is a significant loss when refueling from the vapors that escape when at the pump. So to me it would make sense to not refuel frequently.

88 Wagonman said:

I have also heard that there is a significant loss when refueling from the vapors that escape when at the pump. So to me it would make sense to not refuel frequently.

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That's what those stupid "vapour recovery nozzles" are supposed to be for. But, if they're so good at vapour recovery, why for does the whole damn filling station still smell like fuel?

That, and the people who pull the hose without letting it drain down first - and end up spilling about a cupful of raw fuel on the ground. In 20 years or so, I think all the fuel I've spilled (a drop at a time) will probably fit in a coffee cup with room to spare. I see people spill more fuel than that in one go.

There have been a lot of excellent responses and I really appreciate the input, but I don't know if I am convinced that you would have a significant savings on a 4.0l renix by running the starter with a long crank time, and the engine reving up to 1500 rpm then back down to idle, then switching back to drive and doing it all over again. Maybe I'm just too lazy:dunno:

88 Wagonman said:

There have been a lot of excellent responses and I really appreciate the input, but I don't know if I am convinced that you would have a significant savings on a 4.0l renix by running the starter with a long crank time, and the engine reving up to 1500 rpm then back down to idle, then switching back to drive and doing it all over again. Maybe I'm just too lazy:dunno:

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On the RENIX, I think the "break-even" point for idling would be 5-6 minutes. The "long crank time" you mention is a "feature" of the system (it wants 300rpm from CKP/CPS before it will fire injectors, so it's not dispensing fuel until then,) although it can be mitigated somewhat by replacing/upgrading your mains cables, according to reports I've gotten from the field (and doing so on my own rigs. OEM mains are 6AWG, and I used 1AWG. Much better...)

However, that is a quirk - while a carburettor will be dispensing fuel anytime the crank turns (due to cylinder filling/engine vacuum,) RENIX doesn't actually dispense fuel - or try to light it - until it sees 300rpm and a valid SYNC signal from the sensors. It will try to "guess" if it doesn't see a SYNC signal in fairly short order, but even then it won't do anything with fuel until 300rpm.

5-90 said:

"Driving the speed limit" doesn't automatically save fuel - most vehicles aren't properly geared/tyred for it. It should be close, but it won't be spot on. If you have to go a little faster, move to the left and do so. If you have to go a little slower, move to the right and do so. While the national 55mph speed limit was supposedly passed to save fuel, it does a damn poor job of doing so (most manufacturers gear their vehicles to turn the crank slowly at cruising speed - you may as well be lugging the engine...)
.

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You may want to rethink some of that paragraph. There is no 55mph National Speedlimit, it was repealed in 95'. As it went the 55mph law was effective because the manufactures of the time did two things right, they downsized the cars and regeared them to the 55mph speed limit. It worked and saved countless of lives.

You are right, each vehicle I have owned had a sweet spot where the speed and fuel efficiency curves intersected to give you a speed where the vehicle was most fuel efficient. Personally I found that running 75 though Nebraska in my XJ is not the most fuel efficient, but makes the trip shorter

One thing I have not heard talk of here is the subject of oil. Use as light an engine oil you can get away with. I run 10W30 in all my Jeeps. When I raced, I used 5W20 synthetic with out issue. Same with gear oil; I use 75W Synthetic in the axles.

I also have heard nothing about tires. Pizza cutter tires with an AT design work better for gas mileage that fat MTs because of less rolling resistance and less mass to get rolling.

Ron

here are a couple gas saving tips for ya. TDI, Honda, Mini i could go on. you'll never catch me in a prius(not because its a hybrid)the damn thing is UGLY!!!!!!!