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Customer Discussions > Automotive forum

Question on accelerator/gas pedal and gas usage...

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Showing 1-25 of 31 posts in this discussion
Initial post: Nov 16, 2009 1:18:09 PM PST
Atomic Tofu says:
Hi folks, I'm hoping someone can answer this if the information is out there, but it's in regards to gas usage and how you use the gas pedal.

If someone is in the habit of tapping the gas pedal in tempo with music, let's say, a press/depress every 4 seconds and thinks that every depress is like letting the car coast, so it either saves gas or is even with a steady and unchanging constant press of the foot to the pedal.

Would the above be true?

Or would it be more accurate that a person who presses a gas pedal to maintain constant speed uses less gas than the person who taps the pedal?

The above would be given on a straightaway if a comparison needs to be made just for experimentation and all things constant.

Any info would be helpful. Thanks!

Posted on Nov 16, 2009 1:35:16 PM PST
Poink says:
This answer is just a guess.

I think having the accelerator in a constant will yield better mileage. Tapping it is less efficient.

I try to maintain my gas especially on hilly terrain. Car slows down as I go up but makes up for it as I go down. Biggest waste IMHO is trying to accelerate as you go up hill.

Posted on Nov 16, 2009 1:51:28 PM PST
Last edited by the author on Nov 20, 2009 7:02:13 AM PST
Joe Average says:
You must be dating an old girlfriend of mine. She did this constantly. Made me a very anxious passenger.

First of all it is not good for your engine. Second terrible for all the tight fitting gears and bearings in the transmission and drive axles. You'll wear all sorts of parts so that they get sloppy and it will make the car very hard to accelerate without clunks and jerks in the beginning acceleration process as the gears clash together. An example would be coast down the road a little on a bicycle and then pedal very hard abruptly. There is a hard jerk as the sprockets locks into "drive". The way to make a car last is to gently apply power to increase your speed. If the car has been driven roughly, there is slop in the gears and it will be difficult to accelerate gently. It's hard for me to explain it.

Lastly there might be more pollution from this behavior. The car's computer might be enrichening the mixture (air-fuel mix) to make the engine more powerful during acceleration.

I drive like my car is on cruise control. Ever driven a car on cruise and let you foot gently rest on the accelerator pedal and felt how the computer moved the throttle? I generally get 200K-300K miles on my engines this way and typically beat the window sticker MPG rating by a few miles per gallon.

There are some arguments for abruptly accelerating to your chosen speed with a heavy foot. The throttle plate is opened more causing fewer pumping loses. Your engine is a big air pump. Your throttle plate (attached to your gas pedal or moved by the computer to mimic your foot movements) blocks the air flow to keep the engine at the speeds you choose. This is part of why diesel engines are more efficient I'm told. No throttle plate at all. Your gas pedal is simply adding more fuel to the engine. In a gasoline engine you are adding more air to the engine and the computer adds more fuel to compensate.

Read the forums where the folks are discussing how to get maximum fuel mileage out of their vehicles (called hypermiling or something). Then drive like a normal person (for safety, so the rest of us don't go crazy trying to follow you down the road) keeping what they discussed in mind.

Posted on Nov 19, 2009 6:49:40 PM PST
Louis Allen says:
Your fuel usage will be directly proportional to the amount of gas you give it....Duh! Putting it in and taking it back out is a legitimate regulation technique. Regardless if you hold it steady or duty cycle the throttle, moving a mass at velocity for a period of time uses up energy.
Joe Average has a legitimate point, wear and tear on items like motor mounts are more likely to wear out sooner with the pumping of the throttle.

Posted on Nov 22, 2009 7:45:13 PM PST
Dave says:
Having to replace the motor mounts, tranny or axle from constant on and off application in the manner you describe would kill any fuel savings you were hoping to achieve. They're tons of tips on how to save fuel. Maintaining the car, not driving the car like you stole it and being sensible with your driving habits go a long way.

Posted on Nov 23, 2009 6:29:00 AM PST
Louis Allen says:
I can gain as much as 6 mpg with my pickup truck by hyper driving.

Posted on Nov 23, 2009 5:01:01 PM PST
Atomic Tofu says:
tapping or pumping the gas pedal as you go down the road is called hyper driving?

In reply to an earlier post on Nov 24, 2009 6:28:15 AM PST
Louis Allen says:
No; Hyper driving is getting from one place to another with the minimal use of the throttle.

Posted on Dec 15, 2009 10:15:54 AM PST
Wayne says:
It's not really an issue of tapping vs holding things steady. It's an issue of using gas appropriately. It's the people who keep going from gas to brake who are wasting the most gas. They pay money to burn gas, and then turn it into heat by using their brake pads.

It's best to maintain your speed relative to traffic. Keep a following distance of 3 to 4 seconds, and take your foot off the gas when traffic in front of you starts to slow down a bit. Place light pressure when vehicles in front start to move faster. There are lots of people who are intent on making sure they are the first ones to get to the red light, and will gladly sit there idling, even as you approach the same light at 20 mph from the next lane, reach the intersection 2 seconds after the light changes, and "zoom" past them while they are in the middle of the intersection, even though they are accelerating hard and you are barely touching the gas pedal.

Posted on Dec 15, 2009 3:31:56 PM PST
OldAmazonian says:
On a carbureted engine, pumping the pedal repeatedly for no good reason will cycle the acceleration pump, squirting extra gas into the venturi at each pump. A computerized engine, even one with drive-by-wire throttle linkage, will doubtless do the same thing regarding gas usage even though it uses fuel injection. It's a knuckle-headed way to waste gas and wear out the car needlessly, but if that's your preference then nobody will stop you.

In reply to an earlier post on Dec 15, 2009 3:38:18 PM PST
Lei Lu says:
You need to go to doctor. This is typical ADD syndrom.
Waste gas and wearing off engine are not big deal at all.

Posted on Dec 15, 2009 8:23:17 PM PST
Atomic Tofu says:
Joe Average, Dave, Wayne and confirm what I would have thought :)
I'm sure many of us efficient drivers drive like how Wayne describes, it is the oddballs who do this tapping outside of any flow of traffic.

Lei Lu can waste gas and your engine all you like, be my guest.

In reply to an earlier post on Dec 17, 2009 7:19:56 PM PST
Last edited by the author on Jan 14, 2010 5:46:50 PM PST
I pretty much agree with Wayne & Oldamazonian (so won't repeat what they've said). My rule of thumb is the less braking you do, the more you're making good use of the gas you've burned to go down the road. I don't mind giving the vehicle full throttle to get going on the freeway (when I know I won't be stopping soon) so the engine wear isn't like grandma was always driving it, but I won't do the constant tapping (unless I'm breaking in a new engine or such). Actually giving it gas and then letting off every 5 seconds can be telling your engine "speed me up, but no slow me down, but no speed me up, etc" and the engine does in part start slowing you being a drag on the wheels making you waste some of the gas you put into getting going (unless you have a clutch like a bike does allowing complete freewheeling when you stop pedaling, but most cars don't do that).

I realize most others on the road would not like it if I literally "coasted to a stop" all the time to never touch the brake because of the distance required to do that, but I do like to look as far ahead as possible. If I can cut my speed in 1/2 without braking, I think that's pretty good to not be at either extreme of coasting forever versus locking your wheels 50 feet from a light (like when exiting the freeway, getting down to ~30mph is good, while if your on residential streets, you should be able to slow from ~25 to ~12 mph). For a while I thought downshifting was good, but I've realized replacing all of the brake parts are a lot cheaper & easier than an extra clutch job in the same time period, so I'll leave the engine engaged to help slow me for the gear I'm in, but use the brakes for slowing thereafter. If I know I'll go down a road for 1/4 mile and need to stop again, I'll keep it in a lower gear possibly running the engine faster for that short stretch, then let off the gas where that's like "downshifting" but I never "upshifted". When I see a light changing red 1/4+ mile ahead, I let off the gas like Wayne said. Of course most of the time I do get others who pass me, rush on up to the red light, screech to a stop at it usually pulling in front of me, and about the time I get to it the light it changes, but I still need to fully stop because they're "parked". That forces me to wear out my vehicle because of their wanting to be stupid (unless I luck out with another lane left open, but it seems rare that I get lucky).

In many ways, I actually like roads with stop signs better than lights just because of being able to predict what's going to happen. As I approach many lights, if it's green (and didn't just barely turn green) then I'll start slowing a bit (assuming it'll change), then at a certain point I'll say to myself "I'm going thru" and give it gas again. I hate it when I start slowing, it stays green, still green, then 1 second before I say "I'm going" then it changes (as if the light is a character in a movie saying "Keep going, keep going, Ha, gotcha"). I wish over putting in "red light cameras" as the way of making things "safer", they would put in warning signs of "expect to stop ahead" with the lights blinking 5 seconds before it's going to change ~150 feet back from any light where the speed limit is 40 mph or above. That way we can know sooner and have time to react versus needing to make those last second decisions at high speeds (as well as knowing to stop burning the gas sooner). I realize that's not a government revenue idea, so regardless of being better for everyone it'll probably never happen (even if they have the networking run to every light already along the roads).

Sorry if I've carried on about traffic when this was a gas burning dicussion, but that's where 1/2 your mileage is lost (in all those starts & stops) as well as what really wears out the cars. I wonder if anyone's done a study on how much gas is wasted annually from such?

In reply to an earlier post on Dec 18, 2009 5:52:15 AM PST
Poink says:
The gas (and time) wasted when some reckless driver get into an accident is what gets me.

I can understand unavoidable accident but those caused by recklessness driving (weaving in and out, speeding, following too close, texting while driving, etc.) makes my blood boil. Some create miles of traffic on highways, hours lost per person and undetermined amount of gas wasted.

Posted on Dec 18, 2009 5:57:03 PM PST
You guys are funny, lots of good points made, but the best way to get good gas mileage is to drive like a grandma, steady and slow acceleration without flooring it unless you need to as to avoid an accident. Also if you're thinking about buying a newer car for better gas mileage do the math first, if you find an 1500-3000 dollar car that's older and can get 20-30 MPG it takes a long time for the extra mileage from a new hybrid or whatever to add up to 10-30 thousand dollars worth of extra money for the car, not to mention the price of upkeep. I suppose that's not what this discussion is about but in a way it is, getting better gas mileage is probably less important than deciding not to go out to eat or splurge on a new product of the moment.

Posted on Dec 19, 2009 9:57:10 AM PST
GotSpeed says:
best way to save gas is take off get up to speed quickly and stay steady don't take 1/2 mile to get up to 40. engines work most efficient at full throttle or near full throttle, the thing that hurts fuel millage is tailgating the guy in front of you and always having to hit the brakes. you use the same amount of energy getting the car up to 40 no matter how you do it (slowly or quickly) you lose that energy that you put in to the mass of the car every time you slow down because your about to hit the guy your tail gating, and tap the brakes. the other thing that can help fuel milage is taking turns faster, keeping the velocity of the car up through the turn. slowing down to 5 miles an hour to make a turn on to a side street then having to hit the gas again is wasting gas, if you take the turn at 20-25 and just keep the speed up you don't have to use more gas to accelerate up to 25 again. the other thing you need to look at is get rid of the extra weight you have in the car, if the trunk is full of crap that could be costing you 2-5 mpg having to hull that extra weight around.

In reply to an earlier post on Dec 21, 2009 6:11:26 PM PST
D. Stern says:
All kinds of 'advice' here. "same energy getting the car up to 40 no matter how you do it (slowly or quickly)", thank you as an ExxonMobile shareholder. "help fuel milage taking turns faster... take the turn at 20-25", and thank you on behalf of ambulance-chasers and body-shops across the USA.

In reply to an earlier post on Dec 21, 2009 6:37:01 PM PST
Last edited by the author on Dec 21, 2009 6:41:52 PM PST
GotSpeed says:
or you could drive instead of trying to drive fast on cell phone and take care of your car and taking a turn at 20 won't cause you to wreck your car, i have a blazer extreme s10 that gets 20-23 mpg on a 14 gallon fill up doing 280 miles on a tank. when it was new it only did about 240 (on a good week) when my dad was driving it to work every day.

want some more advice. get a shift kit B&M 70380 ShiftPlus Electronic Shift Improver so your trans doesn't slip so much on shifts(don't conplain when you drop your latte on the 1, 2 shift) get a cold air intake and high flow cats and exhaust. get a set of premium tires (not your 50$ budget tire that squeals around a turn at 10 mph) and a good set of hawk brake padsS10 BLAZER SUV 2WD 05 2Dr Brake Pads - Hawk HPS - Front and bear decela rotors. then you will have spent half of what i have in my truck and maybe you won't wreck your car every weekend. i personally have never been in an auto collision, and the only one that my dad has had was a blow out on the freeway in someone elses corvette (67) that totaled it and put him in the hospital about 30 years ago. so telling me i don't know how to drive when you have never met me is a poor decision. go to a driving school at a track and take some driving lessons and watch some one that really knows how to drive fast maybe you will learn a thing or two. by the way i don't have stock in any of them above mentioned in this post or my previous post.

In reply to an earlier post on Dec 21, 2009 10:43:07 PM PST
D. Stern says:
"watch some one that really knows how to drive fast maybe you will learn a thing or two" My mistake, I thought the discussion was about driving for good fuel economy AND safely.

With most vehicles on the road being some flavor of truck/SUV, high speed turns = bad fuel economy as tires tend to loose traction when facing skyward :-) stats show high rate of roll-overs in these popular and often top-heavy vehicles. Jack-rabbit starts also decrease fuel economy vs. steady acceleration to speed.

OTOH I agree quality tires (properly inflated) are helpful, as I get 34-5 mpg highway (2-3 over rated mpg) and over 500 miles per tank -- Mazda 6i, 4 cyl. manual trans. With split fold-down seats, it has great cargo space (10' dimensional lumber fits with trunk CLOSED), so I don't see any downside to the large 18 gal. fuel tank rarely found in a mid-sized sedan.

In reply to an earlier post on Dec 21, 2009 11:19:08 PM PST
GotSpeed says:
the down side to a large tank is when its full your have a few extra hundred pounds of fuel for nothing other then being able to drive more with out stopping. ask any one removing weight will give you better mileage, the problem with starting slow is on a automatic the torqe converter doesn't lock up till 2,500 - 3k rpm so until then all the power the motor is making is not being used completely to power the car. so slowly taking off lets it slip more(just like driving with a bad clutch or riding the clutch out slowly) more slip means less movement forward for the amount of fuel being used.

honestly people looking for fuel mileage are not in full size suv's, nor does taking a turn at 20 make a full size suv flip, when i talk about taking a turn fast i mean look at where your turning and think about it, if your turning on to a side street and you can clearly see no one around or no one can come out of a blind spot and your going half a block down the road if you take that turn at 20 and coast the street then you make another turn that little bit that you coasted cost you almost nothing in fuel. some cars even when in 3ed and the trans is slowing the car down will let the motor run on just momentum and not give it any fuel until it gets to a lower rpm where it needs fuel to keep the motor running.

knowing how to drive fast makes driving at street legal speeds easier and less stressful and you will be able to focus on the road/traffic around you instead of the car control and what your doing to drive. any thing that you can do at a high rate of speed when you slow it down to you have more control of whats going on, so say you have only driven on suffice streets all the time doing 40 the first time you get on the freeway your tensed up and after a few hours of driving at 65-75 mph you become more relax doing it right? well when you know where the edge of your cars handling is the less stressful it will be when your driving it around other cars because you know where the limit is and it won't surprise you when you pass it. so instead of worrying about over driving a turn you can focus on whats around the turn and whats around your car making you safer driver.

In reply to an earlier post on Dec 22, 2009 7:44:25 AM PST
Louis Allen says:
Sounds like you work for a high performance parts department.

In reply to an earlier post on Dec 22, 2009 7:58:52 AM PST
Louis Allen says:
<<<<<the down side to a large tank is when its full your have a few extra hundred pounds of fuel for nothing other then being able to drive more with out stopping.>>>>>

13 gallon fuel tank full weighs 84.5lbs. (gasoline = 6.5lbs per gallon). A 23 gallon tank will weigh 149.5, only a 65lb. differance, not hundreds of pounds....?

In reply to an earlier post on Dec 22, 2009 10:12:34 AM PST
Last edited by the author on Dec 22, 2009 2:28:59 PM PST
GotSpeed says:
65 pounds differences in the fuel that slouches around is a big difference. larger tank has more room for the fuel to move around and hit the sides of the tank under acceleration and braking. nascar has foam in the tanks for a reason. it would be like taking off and 2 feet after you take off you just a jerk backwards when the fuel hits the end of the tank and starts moving, 65 pounds of fluid moving about is a huge difference.

i work in the tech industry fixing computers/printers/scanners for large corporations and banks. nothing to do with performance parts, automotive stuff is just a hobby for me.

In reply to an earlier post on Dec 22, 2009 3:30:09 PM PST
Louis Allen says:
I work for an automotive tech school in NJ. I teach all of the automotive disciplines, I specialize in electronics and performance. I am a recertified ASE master auto tech with twenty years working on European cars. For hobbies, I own and operate my own aircraft, motorcycles and power equipment. I also dig astronomy.

In reply to an earlier post on Dec 23, 2009 6:49:59 AM PST
Last edited by the author on Dec 23, 2009 6:52:35 AM PST
Poink says:
@Louis Suvoy

I use my tachometer as a reference when accelerating. I try to stay between 2000-3000 rpm (mostly 2500 on my current car). Cruising, I usually stay around 2000 rpm

Proper speed at turns are affected by many factors;
driver skill
road condition
road super elevation
turn radius
vehicle condition
vehicle center of gravity
tire size/kind/condition
strut condition

To make a hard speed recommendation w/o considering all these variables is irresponsible.
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Discussion in:  Automotive forum
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Initial post:  Nov 16, 2009
Latest post:  Dec 26, 2009

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