driving efficiently

[ScottyB]

Well, I am sure injectors shut off on cars that advertise that injectors shut off, but I don't think they all shut off, and I dont think this is in any vehicle except direct inject vehicles. At coast, i think every other vehicle is using the same amount they take to idle

yeah see i had no idea about that...kinda thought it was a normal thing to have them shut off. ASSuME'd

[Kaan]

anyone ever thought about cold air = dense air... your OBD computer might be measuring that and adding more fuel so you dont run lean ?

edit: also, wouldnt denser air cause your drag coefficient to go up?

[WRXtranceformed]

I did some looking around on the EPA website, and there is some information there about the winter fuels. I guess they were designed to help reduce emissions during the winter months. Do a google search and it will turn up some stuff.

[Sijray21]

cool Scotty - i've done most of the techniques you mentioned. i just found overall that the less my foot is on the gas in any situation the better - simply more coasting (...go figure...[/sarcasm]).

Coming from 50/66 to the Oakton House i noticed that a significant portion was downhill so i used to try and see how far i could get without touching the gas. After about a week of consistently doing this i noticed about 10-20 miles more per tankful (granted there were a lot of other factors :-P ), but that's pretty cool.

I'm just happy i can fill up using 87 octane with the teg.

[WRXtranceformed]

*sigh* none of the PDF files I downloaded on gas quality will open up on this computer, but I did find these tidbits from a CBS news report, which confirm what we've all said: yes gas comes from central sources, but top tier gasoline includes cleaners and additives that help your engine run cleaner and more efficiently. Therefore, not all gas is created equal (when it hits the inside of your fuel tank).

Right! But is discount gas really the same as brand-name gas ÔÇô even though it sometimes costs up to 20 cents a gallon less?

The reality? The answer is both "yes" and "no."

"Gasoline comes from just a few terminals, yes" said California Energy Commissioner Jim Boyd.

Different distributors do fill up their tanker trucks at the same terminal. But brand names argue they have a higher quality because they put more additives that help the car's engine run clean.

But discounters like Costco say it doesn't matter.

That wasn't the case back in 1979, during the energy crisis when people ruined their engines buying unregulated discount gas. Now, even discount gasoline must meet minimum EPA standards.

"Cheap gas will more likely foul up the spark plugs... not immediately, but in due time." said Otto Lopez, an independent mechanic.

None of the name brand gas companies we contacted would talk to CBS News about why their gas is better.

But some automakers ÔÇô like BMW, General Motors, Honda and Toyota ÔÇô have recommended a list of stations that provide what they call "top-tier" gasoline, which includes QuikTrip, Chevron, Conoco, Phillips 66, 76 , Shell and MFA Oil Company.

If you do buy discount gas, the experts recommend buying a detergent additive and pouring it into your tank every few thousand miles. They also suggest hitting the brand names for a fill up occasionally for the cleaning additives.

Here is the full list of top tier gas companies:
QuikTrip
Chevron
Conoco
Phillips
76
Shell
Entec Stations
MFA Oil Company
Kwik Trip/Kwik Star
The Somerset Refinery, Inc.
Chevron-Canada
Aloha Petroleum
Tri-Par Oil Company
Shell-Canada
Texaco
Petro-Canada
Sunoco-Canada


And from the Wikipedia on "Top Tier Gas"

Why Detergents in Gasoline
Without some level of detergents engine deposits form in most vehicles and this causes reduced fuel efficiency, acceleration and power as well as increasing emissions and rough idling.

Top Tier standards also require the presence of ethanol in concentrations between 8 and 10%. [7]


[edit] What Vehicles Will Benefit from Using This Gas
All vehicles will benefit from using Top Tier Detergent Gasoline over gasoline meeting the lower EPA standard. Deposits will be minimized on fuel injectors, intake valves, and combustion chambers.[8]

New vehicles will benefit by keeping their engine clean and running optimally, older vehicles will benefit with increased engine performance and prolonged vehicle life.

Using this gas will have the following benefits over gasolines just meeting the EPA standard:

Improved fuel efficiency
Reduced driving upsets (rough idle, stalling and surge)
Improved acceleration
Increased engine power
Reduced emissions

[ViPER1313]

The only thing I have ever noticed to cause a large increase in fuel economy is traveling at slower speeds on the highway. 65 in the Rabbit / SHO will equate to 28/24mpg respectively. Prolonged trips at 80 to 85 mph will net about 21mpg / 18mpg for the same two cars. It really hurts the Rabbit - the engine has to turn 3600/3700 rpm opposed to 2800 at 65.

[HAULN-SS]

to Jray - doesn't matter as much as far as cost to pay 10% more a tank at 3$/gallon than it does to pay 30% more per tank at 1$/gallon. The higher gas goes, the more people should switch to premium.

[WRXtranceformed]

It really hurts the Rabbit - the engine has to turn 3600/3700 rpm opposed to 2800 at 65.

That brings up another really good point: gearing. I don't think I've ever heard about someone swapping out their gears to less steep ones just to get better gas mileage...the cost of it would probably take a long time to make up in gas savings. I do know of people unwilling to change the gears in their performance car to steeper ones because they daily their car and want it to get reasonable mileage. My IS auto comes with 3.93s iirc which is pretty steep but helps the acceleration. If it had something like 2.72s I'd probably get a few mpg more. It all depends on what you've got in your car.

[Evan]

its not just gearing, dont forget the role of wind resistance in fuel mileage.
the power needed to push an object through the air increases as the cube of the velocity. ie - double the speed, quadruple the drag.

Remember physics class?
4x drag = 4x work done twice as fast so it requires 8 times as much power.

[WRXtranceformed]

True, there are so many factors aerodynamically and related to the drivetrain of a car that influence gas mileage. However, gears are something you could change; you can't make a Dodge Ram into an Indy car aerodynamically :lol:

[Ginger]

*edit*

Irrelevant

[.RJ]

I don't think I've ever heard about someone swapping out their gears to less steep ones just to get better gas mileage...the cost of it would probably take a long time to make up in gas savings.

Most 1/2 ton and larger trucks come with several rear end gear options - it becomes pretty important when towing.

My truck has a 3.55:1 gear, but I'd really like something a little shorter - If I want to tow in OD, then I have to keep the speed over 70, and gas mileage takes a hit.

[WRXtranceformed]

Yeah, if you could do it from the factory that would be ideal. Some cars have really cheap gear options too... it's like $250 to install steeper performance gears in Stangs for example. In WRX / STis, it's like 5 grand!

[HAULN-SS]

Lots of MCSS guys that daily drive their cars keep two rears on hand - the originals were 3.73, but the LS's came with 2.52 or something, and this nets them a couple mpg. You can buy a rearend for like 300$ or something.

Also - evan, are you sure that's right? I thought twice the speed = 4x the power. You're increasing drag by two, and going moving the object twice as fast = 4x power.

[Evan]

you're thinking of force. The force required (or in automotive terms, torque) would be equal and opposing force to drag and is 4x.

Since power is a component of work over time, going twice as fast (and half as much time) = 8x power.

[Mike]

i turn my car off any time i know i'll be sitting stopped for more than 10 seconds. yes, that includes stoplights.

[PDenbigh]

Maybe some of the tuning guys can chime in here - but with the XR it has a startup enrichment that dumps in more fuel at start. It would be interesting to see at what point it is more efficient to let your car idle (low load, less fuel) rather than stopping it and starting it (and thus dumping a bunch of fuel in to get it going).

[Mike]

is that thing a diesel? i'm pretty sure modern fuel injection doesn't do that.

[.RJ]

i'm pretty sure modern fuel injection doesn't do that.

All FI'd cars have a rich 'cold start' cycle.

[Andy]

i'm pretty sure modern fuel injection doesn't do that.

All FI'd cars have a rich 'cold start' cycle.

Cold start being the operative word. If mike doesn't care about burning his starter, his car isn't dumping in more fuel on startup once the engine is warmed up.