Squeezing out every Nickle - 2000 Honda Civic Auto

[Scott_in_Tulsa]

Greetings to the group! I am new to GasSavers but have already gained a lot of insight from reading the articles and past Forum responses and topics.

Two months ago, I traded off my 2002 Chevy Impala 6 cyl auto for a 2000 Honda Civic Coupe EX auto. The main reason was to get a vehicle I could have paid off quickly (actually paid it off this week) and be able to run for several years with excellent gas mileage.

With my Impala, I was able to average 28.3 mpg with 90% highway driving. When I say highway, I basically mean interstate where you average 70 mph just to keep up with the flow of traffic.

Right now, I am averaging between 34 and 35 mpg with my Honda. I think that will continue to improve as the weather warms up and I don't have to run the heater and defrost so much. The greatest change I have made to improve fuel efficiency is to learn how to properly do a neutral coast with a running engine. I have some good straight stretches of road that is a gradual decline. I can usually get in a count of 10 before I have to kick it in drive and accelerate to maintain momentum.

With the neutral coast, I generally drop my RPMs from 2000 RPMs in drive with my foot off the gas to around 800 - 1000 RPMs in neutral. So far, the benefit is about a 2 mpg improvement in my fuel efficiency.

I would guess that I am only able to coast about 10% of the time. The rest of the time, I try to keep my average speed at 68 mph or less with my RPMs below 2800 (preferably around 2500).

I would love to talk to anyone that has experience boosting fuel efficiency in auto trans vehicles without making major mechanical modifications. The one thing I will refuse to do is pay for modifications to my vehicle that will take more than 3 months to recoup in gas savings.

Looking forward to learning more from the group here.

Scott
Tulsa, OK

[Lug_Nut]

When coasting in drive at 2000 rpm you are probably using zero fuel. Fuel injection systems typically shut off all fuel delivery on over-run or engine brake conditions versus maintaining some amount of fuel needed to maintain idle in neutral. Whether one technique is more fuel economical than the other isn't the gallons used, it's the miles coasted. Neutral will produce more distance but uses more fuel. In drive (or in gear for manuals) will use less fuel, but also produce less distance.
My last automatic equipped car was an 84 Volvo 760 with the peugeot/renault/volvo 2.8 V6. Attempts at getting that over 20 mpg average included removing the accelerator pedal mounted 'kick-down' linkage to the transmission. It shifted down to first and started off the line normally but then went secondthirdfourth (that quickly) at 10 mph. I had to move the lever through the selector manually to hold each gear long enough to build speed. It did mean that there were no more downshifts from 4th to 3rd on slight rises, but it was altogether an unpleasant experience and gained me little in fuel savings.
Big car, thirsty engine, small tank. I'd get maybe 200 miles per fill-up.
My Passat is bigger, seats aren't quite as nice, but damned close, performance is better, tank is HUGE, and the engine sips fuel to get 1000+ miles per fillup.
But I'd still personally prefer the convienience of an automatic.

[Scott_in_Tulsa]

Can anyone else weigh in on the comment provided by Lug Nut?

Does a gas engine really use zero fuel when you have the trans in drive but let off the gas pedal entirely?

Does having an auto trans in neutral really use more gas than with it in drive and your foot off the gas pedal?

I don't understand the sentence "Whether one technique is more fuel economical than the other isn't the gallons used, it's the miles coasted." Isn't the whole point of FE to use less gallons and thereby be more efficient? Doesn't additional miles coasted help improve FE and reduce number of gallons used?

I am confused. Hopefully someone else can weigh in with more thoughts on this.

[Lug_Nut]

Electronic fuel injected cars shut off the injectors when the engine speed is greater than the request. This does not hold true for carbureted engines, or possibly for older mechanical fuel injection systems.

Here's a theoretical scenario that may help explain my comments:
2 mile route, one mile gradual downhill followed by 1 mile on the flat.
A) In gear, foot off the accelerator, coasting with engine braking, speed doesn't increase. No fuel consumed for first mile, then usual fuel consumption for the last mile.
B) In neutral, foot off the accelerator coasting, no engine braking, higher peak coasting speed. Some fuel used for the first mile and 1/4 mile of the flat, then usual fuel consumption for the last 3/4 mile.
Which used less fuel?
I can't give a blanket statement answer other than to say that:
if you can coast fast enough that you use your brakes to keep from going too fast, leave it in gear and use engine braking.
if you have to add accelerator because engine braking effect slows the car more than desired, then neutral is probably more fuel economical.

[GasSavers_Ryland]

Originally Posted by Lug_Nut

Electronic fuel injected cars shut off the injectors when the engine speed is greater than the request. This does not hold true for carbureted engines, or possibly for older mechanical fuel injection systems.

Not to sidetrack the topic, but even some carburated cars cut fuel while coasting in gear, Honda started doing this with their carburated engines in the mid 1970's, the fuel would be cut if you were going over 12mph, and the engine was warm, had oil pressure, was in gear, and that a few other sensors basically saying that everything was ok, and I know that this carries true thru current models that have manual transmissions, and if I remember correctly others have confirmed that this is true for Honda's that have automatics as well.

[Scott_in_Tulsa]

Originally Posted by Lug_Nut

Electronic fuel injected cars shut off the injectors when the engine speed is greater than the request. This does not hold true for carbureted engines, or possibly for older mechanical fuel injection systems.

Here's a theoretical scenario that may help explain my comments:
2 mile route, one mile gradual downhill followed by 1 mile on the flat.
A) In gear, foot off the accelerator, coasting with engine braking, speed doesn't increase. No fuel consumed for first mile, then usual fuel consumption for the last mile.
B) In neutral, foot off the accelerator coasting, no engine braking, higher peak coasting speed. Some fuel used for the first mile and 1/4 mile of the flat, then usual fuel consumption for the last 3/4 mile.
Which used less fuel?
I can't give a blanket statement answer other than to say that:
if you can coast fast enough that you use your brakes to keep from going too fast, leave it in gear and use engine braking.
if you have to add accelerator because engine braking effect slows the car more than desired, then neutral is probably more fuel economical.

Lug Nut,
Thanks. Your additional explanation made a lot more sense to me. I still don't totally understand why the engine won't die if you cut off the fuel for electronic fuel injection when in drive with your foot off the accelerator but your example did make sense to me.