What's more economical? Full throttle or accelerate slowly

[Marshall Grice]

BTW I have seen some of the high miler groups advocate putting the car in gear and driving away as soon as possible after start up.
This is bad news for engine longevity. There is very little oil protection available at start up. Adding load to the engine will cause increased wear.
I always start, then put my seat belt on before even putting an auto in gear.

i'm curious where you get that idea from? If you're car takes more then like a second to build oil pressure there are larger issues at hand.

it's not like you're cranking the engine with the car in gear with clutch released.

[Stephen Yeoh]

What about coasting while IN gear instead of going to neutral? I also read that all cars made from something like 2000 on will shut off fuel delivery if you are coasting while in gear. However, if you shift to neutral, some fuel is needed to keep the engine idling. The computer in my 06 GTI shows instantaneous mileage going infinite when I lift off the throttle completely while staying in gear.

[Marshall Grice]

What about coasting while IN gear instead of going to neutral? I also read that all cars made from something like 2000 on will shut off fuel delivery if you are coasting while in gear. However, if you shift to neutral, some fuel is needed to keep the engine idling. The computer in my 06 GTI shows instantaneous mileage going infinite when I lift off the throttle completely while staying in gear.

yeah but the friction from spining the engine generally outweighs any fuel savings between shutting off the injectors and coasting in neutral.

ie. you will come to a stop faster and thus need to get back on the gas sooner if you coast in gear.

[Kurt Rahn]

What about coasting while IN gear instead of going to neutral? I also read that all cars made from something like 2000 on will shut off fuel delivery if you are coasting while in gear. However, if you shift to neutral, some fuel is needed to keep the engine idling. The computer in my 06 GTI shows instantaneous mileage going infinite when I lift off the throttle completely while staying in gear.

Depends whether you're using the engine to brake or trying to coast a god distance. If you remain in gear, the fuel does shut off, but you're going to reduce momentum in the car pretty quickly, so any milage you gain will be wiped out if you have room to coast for a good distance.

Whoops...what Marshall said.

[George Schilling]

What about coasting while IN gear instead of going to neutral? I also read that all cars made from something like 2000 on will shut off fuel delivery if you are coasting while in gear. However, if you shift to neutral, some fuel is needed to keep the engine idling. The computer in my 06 GTI shows instantaneous mileage going infinite when I lift off the throttle completely while staying in gear.

Depends whether you're using the engine to brake or trying to coast a god distance. If you remain in gear, the fuel does shut off, but you're going to reduce momentum in the car pretty quickly, so any milage you gain will be wiped out if you have room to coast for a good distance.

Whoops...what Marshall said.

Yeah but if you have God on your side........anything is possible.

[Kurt Rahn]

LOL, the one time I misspell something and I get caught.

[Q V]

For the orange beast, staying light on the throttle helps tremendously. Of course, I have a custom ecu, tune, and aftermarket turbo w/ ridiculous injectors, lol.

With my automatic, it's basically impossible to be heavy on the throttle and have the car shift early - i.e. anything more than 1/3-1/2 throttle will make the car shift 3.5-4k+ rpm. When I do the "light acceleration" it will stay between 2-3k depending on speed build up.

On a side note, UPS saves fuel by making more right turns than left in its routes: http://abcnews.go.com/wnt/story?id=3005890.

[B K]

Hydraulic regeneration http://www.wired.com/autopia/2008/10/ups-hydraulic-h/" onclick="window.open(this.href);return false;
+
Mazda's starterless starter http://www.wheels.ca/article/32454" onclick="window.open(this.href);return false;
+
methanol injection = hybrid car without the need of heavy/expensive batteries....just heavy/expensive hydraulic cylinders.

[Reijo Silvennoinen]

Interesting that the talk is of full throttle starts. Like John said, the enrichment that happens at full throttle may not be good for fuel economy.

However what I do remember reading quite a few years ago (sorry, don't remember where the article was), was that "brisk acceleration" yielded better fuel mileage than light acceleration and the reason given was that the vehicle would be in a higher gear, sooner. So this is the way I drive currently and always exceed the vehicle mileage ratings of whatever vehicle I have owned since that time.

Also, I drive "lines" around curves and don't slow down much - keeping it in higher gears....often watching others in the mirrors catching me coming up to corners ... and then they fall "way" back through the corner and "painfully" slowly catch up to me on the following straights...... I don't downshift much for the corners.....sometimes maybe to 4th etc. (from 6th in the S2k) depending on the corner, of course... The problem is driving too fast and wearing out tires though.

One interesting anomaly in my past was the '88 Daytona turbo coupe that I had. On the highway driving at 60 mph it got worse gas mileage than at 80 mph. The gearing was such that it was "lugging" in 5th gear at 60 mph and fighting a losing battle to hills. So what I do now on hills (on steeper/more significant ones...) is downshift so that the vehicle does not have to work as hard to get up the hill. Generally I judge this by what position I have to hold the throttle at in order to hold the speed that I'm maintaining. If I have to give less throttle in 4th than in 5th, then I will run up the hill in 4th etc. This helped in the Daytona.

Oh yeah, I also often skip gears when there is no one near me and I'm not in a rush to merge or whatever.....rev it up in 1st and 2nd and then start skipping gears....4th...6th........or 1-2-3-6.

Reijo

[John Prosser]

BTW I have seen some of the high miler groups advocate putting the car in gear and driving away as soon as possible after start up.
This is bad news for engine longevity. There is very little oil protection available at start up. Adding load to the engine will cause increased wear.
I always start, then put my seat belt on before even putting an auto in gear.

i'm curious where you get that idea from? If you're car takes more then like a second to build oil pressure there are larger issues at hand.

it's not like you're cranking the engine with the car in gear with clutch released.

It is not an idea, it is a fact. The majority of engine wear occurs during initial start up. This has been exhaustively studied, reviewed and published. If you look a t an oil pressure gauge while starting a vehicle you will see that oil pressure does in fact take seconds (how many??) to build. All I am saying is, that to ensure longevity, it is a good practice to at least have full oil pressure before putting a vehicle in gear and / or driving off.

[Aaron Goldsmith]

It is not an idea, it is a fact. The majority of engine wear occurs during initial start up. This has been exhaustively studied, reviewed and published. If you look a t an oil pressure gauge while starting a vehicle you will see that oil pressure does in fact take seconds (how many??) to build. All I am saying is, that to ensure longevity, it is a good practice to at least have full oil pressure before putting a vehicle in gear and / or driving off.

That usually seems to be attributed more to being an issue of tolerance change due to temperature based expansion than oil pressure. Though if the car sat for a long enough the engine would be pretty dry the first few revolutions.

[George Schilling]

It is not an idea, it is a fact. The majority of engine wear occurs during initial start up. This has been exhaustively studied, reviewed and published. If you look a t an oil pressure gauge while starting a vehicle you will see that oil pressure does in fact take seconds (how many??) to build. All I am saying is, that to ensure longevity, it is a good practice to at least have full oil pressure before putting a vehicle in gear and / or driving off.

That usually seems to be attributed more to being an issue of tolerance change due to temperature based expansion than oil pressure. Though if the car sat for a long enough the engine would be pretty dry the first few revolutions.

Who needs a study? Seems to me to almost be self-evident that giving the engine a few moments to get oil circulating is a good idea.

[Steve Ekstrand]

On a hybrid where the engine goes on and off I wonder if they can, (should, maybe have) put an electric motor in to pre-spin the oil pump.

[Marshall Grice]

On a hybrid where the engine goes on and off I wonder if they can, (should, maybe have) put an electric motor in to pre-spin the oil pump.

it's really only cold starts that have any measurable effect on engine wear. I would be far more concerned about an electric oil pump pre-spinner failing and somehow damaging the oil system then i would be about potential engine wear.

even with a hybrid system, it would still be a challenge to get any real engine load applied before oil pressure wouldn't be sufficient to support that load. Something along the lines of a cold start at WOT is about all i'd be worried about.


if you're really that concerned about only getting hundreds of thousands of miles of engine life then you should be pre-heating all of your drive train fluids anyway.

[Bob Beamesderfer]

BTW I have seen some of the high miler groups advocate putting the car in gear and driving away as soon as possible after start up.
This is bad news for engine longevity. There is very little oil protection available at start up. Adding load to the engine will cause increased wear.
I always start, then put my seat belt on before even putting an auto in gear.

i'm curious where you get that idea from? If you're car takes more then like a second to build oil pressure there are larger issues at hand.

it's not like you're cranking the engine with the car in gear with clutch released.

It is not an idea, it is a fact. The majority of engine wear occurs during initial start up. This has been exhaustively studied, reviewed and published. If you look a t an oil pressure gauge while starting a vehicle you will see that oil pressure does in fact take seconds (how many??) to build. All I am saying is, that to ensure longevity, it is a good practice to at least have full oil pressure before putting a vehicle in gear and / or driving off.

Wear on bearings or cylinder walls?

[John Coffey]

It is not an idea, it is a fact. The majority of engine wear occurs during initial start up.

Well, the real answer is: It depends mostly on the type of fuel used. Per a number of studies published on the SAE web site the biggest wear issue has to do with the fuel washing oil off the cylinder walls in the first couple seconds of startup. Ethanol/Methonal are be far the worst (by orders of magnitude) with LPG a distance second, Gasoline third, and Diesel fourth. A lot of the oil companies quote this study in their sales and marketing literature fine print:

http://www.sae.org/technical/papers/850215" onclick="window.open(this.href);return false;

This study is specific to very cold starts (Canada) on pure Methanol fueled engines. This is the most extreme example and is far from typical. From this study some claim that cold starts will remove .001" of ring material every 1,000 cold starts or 1,000 miles of operation while the engine is cold.

[Reijo Silvennoinen]

Thanks John - that's quite interesting. +25 deg. C is 77 deg. F by the way and -40 C = -40 F (that's where the thermometers read the same).

Notably most people have their vehicles inside a garage and/or plugged in (block heater) when it is -40 C/F.....since the likelihood of starting begins to be remote (no pun intended). However sometimes when away from home, a vehicle may sit outside in very cold weather such as -40 (don't think I ever saw anything this cold in the 18 or so years I've spent in Calgary....but have seen it elsewhere....and in the northern Arctic it is common to see even colder temps - -50's. God, I feel cold just talking about it!

Interesting.

R

[Karl Asseily]

I've read maximum fuel efficiency is achieved by maintaining almost full throttle up to a very low engine speed, generally around 2,000 rpm.

In my M coupe I can exceed 21 mpg in the city doing this versus 17 mpg driving "normally" and shifting around 3500 rpm (or 15mpg shifting around 4500.) It just isn't any fun. In the truck, driving with nearly full throttle and letting it shift at 2100-2200 rpm (it's a small V8), I get at least three or four more mpg versus accelerating very slowly with revs below 2000.

Mike

Patch,

remember that day we had to shift at 1,400 rpm to get to the gas station at qualcomm? That was the best mpg i've ever seen !

[John Prosser]

Thought for the day.

Don't think MPG, think GPY.
Gallons per year.
A cleverly assembled group of vehicles ranging from motorcycles through motor homes, used appropriately, may allow you to consume the same or less fuel as your neighbor while having way more fun.

Just default to the most efficient vehicle for the job at hand.

Need milk? Ride the scooter. 6 Kids to soccer, break out the suburban. Whole family camping, load up the motor home.

Of course don't try this if you live in Cali. Due to our onerous vehicle licensing costs.

[George Schilling]

Of course don't try this if you live in Cali. Due to our onerous vehicle licensing costs.

Between license fees, sales and fuel tax, it wouldn't surprise me if the total tax during the life of a vehicle exceed the purchase price. And this is the good news.