There is no logic...and he's right in that shifting into and out of drive while moving is bad for your tranny....

Red/Canadian

 

that's a good thing to know.. thanks.

'03 G35 Sedan: ivory/aero body/sport/sunroof
Warning: Objects in mirror are FASTER than they appear

 

Yeh, I do the same at lights man, it also helps keep the battery fully charged instead of idling down further in Drive.
About coasting- well like I said it was recommended to me to not do it. But I don't fully understand it either because 6M/T coast too, a little. Don't worry about it. It's not the worst thing to do, I'm sure. If you are worried, then ask a tech at the shop.
He should know whether it's good, bad , or doesn't matter.
By the way in my opinion when you're at a light and idling in neutral the rpm's are a bit higher so you're burning more gas. I click it into 'N' to not labour the motor or tranny, and unecessarily discharge the battery. With charging systems as good as they are nowadays, what I do is probably not necessary. It's just habit.

Gsedanman--in Silverstone Coupe clothing.

 

Higher RPM doesn't automatically mean more gas used. In neutral, there's less load on the engine, so it requires less fuel going into the cylinder to maintain the speed. So the cylinder is sparking with less fuel, but more often. Depending on how much less fuel and how much more often, it might be using the same or less fuel per time period.

Same thing goes with travelling uphill/downhill as opposed to a level road. Say you're going 60mph, at 2200RPM. It requires more throttle, and more fuel in the cylinder per revolution to generate the extra power required to maintain 60mph on an uphill slope, even though the RPMs are the same. Likewise, it takes less to maintain on a downhill slope - you might even be gaining speed with your foot off the gas.

I'd say the theory on not running around in neutral is sound. Tow trucks take care to lift the drive wheels, and let the other wheels roll for the same reason - don't want to damage the drivetrain. AWD vehicles have to be towed on flatbeds for this reason. Plus, if another driver does something stupid they'll catch you off guard and out-of-gear, and you may not be able to avoid an accident.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

Check your odometer. Mine reads 3 percent lower than actual when compared to measured distance or gps. Helps the fuel calculation a little.

 

So you're correlating idling at a stop in Drive to labouring up a hill and having to gas a little more to maintain your speed? I don't know about that. To my mind the engine at idle whether in drive or neutral isn't labouring at all. It's just at a different rpm. (albeit a very little difference) The only difference being that the friction in the tranny is slowing the engine down. In Neutral- no friction, higher rpm's> more gas.
Not sure tho. I'll think on that and see what my 'pea brain' can come up with........Interesting.......

That's a good point about coasting and not having as much control over the car as you should. Sometimes you need to gas it, sometimes you need to brake it. Good to have that option...........Later........

Gsedanman--in Silverstone Coupe clothing.

 

Good point about odo error. My Sedan's odo/speedo had an error of about 3%. The Navi was more accurate but not the same as my hand held Lowrance GPS. Between the 2 GPS's there was a 1% variance.
Haven't had a chance to check my Coupe yet, but I will.
The other thing that effects odo/speedo error is tire diameter. The snows I have on the Coupe aren't the same as the stock tires. They're close but not the same- so there's 1-2%.
Bigger changes in diameter will net more error.

Gsedanman--in Silverstone Coupe clothing.

 

Not really correlating the two, just using the hill as an alternate example of RPM not being an exact indicator of how much fuel is being consumed per minute. At stop in drive, there is some (albeit not a lot) extra load on the engine, so it is labouring a bit more than it would in neutral, though I doubt it's actually enough of a difference to notice a change in fuel consumption.

Plus, on the coasting issue, in some states in the US it's actually illegal to coast on the road in neutral, though I'd like to see them prove you're doing it.

Back to the original topic of this thread, my first two tanks where at about 15mpg, and the third looks like it's going to come in at 17, though we did take a day trip up to Carlsbad (about 35 minutes each way) -- so that was a minor highway jaunt thrown in. Spent the day at Legoland. Even with the sport suspension, the highway ride was more comfortable than my old 92 Accord (probably because it's seats sucked).

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

Like I said, the load on the engine at idle- I'm having difficulty with that. I'll have to 'chew' on that for a while.
It's probably illegal here in Canada too. No real need to coast anyway, and as you said how would they prove it?
Your mileage is low for warmer climate. My Coupe's consumption is similar to your Sedan's, but the weather isn't. It's cold as a witch's TT (most days it's below freezing, most nights it's really cold) which will cost in mileage .Mine also isn't broken in yet: 300miles.
Last summer on long trips my Sedan really got good gas mileage. At a steady 65-70 mph, I'd get more than 26 for a 300 mile trip. Short trips got me about 22-23 (in your size gallons).
Talking about gas--I'm tapped..........Later............

Gsedanman--in Silverstone Coupe clothing.

 

Yeah, my mileage does seem low. I'm hoping it picks up a bit soon. Gas isn't cheap in San Diego.

Now that I think about it, the engine also has the fan, alternator, A/C compressor, etc. to deal with even in neutral. Sticking it in drive probably doesn't add much to the load that's already there. But it does add something to the load, measurable if not noticeable.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

I have just over 1000 miles on my '03.5. Last two tanks have netted 16 mpg with 90% city driving. The G isn't known for its fuel economy as most mag reviews will attest. Still...I hope it improves!

As for going down parking ramps I always wait at the top til there's a strong tailwind before proceeding in gear. Then I ease off the brake peddle gently so as not to cause any unnecessary friction. I find that using Armor All on the tire tread also increases mpg on downhill endeavors.

HTBomb's Magical Hot Wheels

 

hahaha. Suggestion: shut the engine off next time. That'll save ya gas!!!!!!!!!

Gsedanman--in Silverstone Coupe clothing.

 

Armor All is good, but try a Silicon coating next time. That'll break your breaking distance up to twice what it is now.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

Better gas mileage coming soon. Just made the first road trip to San Francisco and Reno before returning to San Diego. I noe have just under 5K on my G35. I averaged better than 25 MPG at 75 MPH+ and the city driving afterwards has been up 15% to 22.5 MPG for the last three tanks. I have been using using 91 octane and have a mixed commute. I think it will do better if I keep my foot off the gas...yeah right.

G35/S/MT....this car rocks!