New 330 getting 11-16 mpg

[epj3]

Guys... you still don't get it. "Performance car" does NOT EQUAL BAD GAS MILEAGE!!! If by "performance car" you mean a 6 liter Vette or 8.whatever liter viper, then yes it means worse gas mileage than a honda civic. But foreign cars that reach for high horsepower per liter are not necessarily inefficient. In fact, to GET a high horsepower per liter mark, you have to try for the most complete burn of fuel which means in the end, you should use LESS fuel. That is why the 600 pound heavier E46 330ci with 220 hp gets the same gas mileage my '88 325is with 164 hp got.

Even when I see a red light ahead I put the car into neutral and coast to a stop! I do that because i know the automatic downshifts douring braking, wasting more gas.

You're actually wasting gas doing that!!! Yes, the transmission downshifts, BUT the reason it does that is to use the engine's compression to slow down.

Think of it this way - when you take your foot off the gas (at say, 35 mph) and the engine does NOT need to do ANYTHING, there is NO GAS going into the engine at that point. If it kept adding fuel, it would add power and the car would keep moving. If you put the transmission into neutral, it forces the engine to have to maintain an idle. When the engine idle's, it uses fuel to keep it idling. The whole idea of the transmission downshifting automatically is to keep the car in the proper gear, but it also prevents the engine from using gas to maintain an idle. If anything, the transmission automatically downshifting actually SAVES gas...

The only time gas is going into the engine is
-Idling
-When your foot is touching the gas pedal

 

[drkeng]

Right now, my OBC reads average 18.7 mpg. I have about 20K miles, probably drive 70% highway. Frequently put the steptronic over to "S" mode and use premium gas.

Going to visit my son up in Eagle River, WI--about 350 miles--and taking the 330(!!). Will check the highway mpg along the way and post results. This will likely be average speed of 75mph (hopefully more).

 

[skolbe]

I just picked up my 330xi 6M E90 - last weekend. The OBC was 12mpg when I picked it up. But in 350 miles it has worked it's way up to 18.7mpg already.

 

[wistarf]

Guys... you still don't get it. "Performance car" does NOT EQUAL BAD GAS MILEAGE!!! If by "performance car" you mean a 6 liter Vette or 8.whatever liter viper, then yes it means worse gas mileage than a honda civic. But foreign cars that reach for high horsepower per liter are not necessarily inefficient. In fact, to GET a high horsepower per liter mark, you have to try for the most complete burn of fuel which means in the end, you should use LESS fuel. That is why the 600 pound heavier E46 330ci with 220 hp gets the same gas mileage my '88 325is with 164 hp got.



You're actually wasting gas doing that!!! Yes, the transmission downshifts, BUT the reason it does that is to use the engine's compression to slow down.

Think of it this way - when you take your foot off the gas (at say, 35 mph) and the engine does NOT need to do ANYTHING, there is NO GAS going into the engine at that point. If it kept adding fuel, it would add power and the car would keep moving. If you put the transmission into neutral, it forces the engine to have to maintain an idle. When the engine idle's, it uses fuel to keep it idling. The whole idea of the transmission downshifting automatically is to keep the car in the proper gear, but it also prevents the engine from using gas to maintain an idle. If anything, the transmission automatically downshifting actually SAVES gas...

The only time gas is going into the engine is
-Idling
-When your foot is touching the gas pedal

EPj3 makes a seemingly logical point about gas consumption during idle. I don't know if he's right, but it doesn't matter because he's overlooksing something vastly more important.

If we consider how much gas is needed to go a given distance, rather than focusing only on when the engine uses gas, and I think we will see that in general, coasting in neutral will indeed save gas.

Why? Because if you remain in-gear with foot off the gas, the engine and drivetrain will quickly dissipate (waste) all of your kinetic energy in the form of heat - energy gained by earlier putting your foot on the gas. Your car will soon slow to a crawl and you will need to get on the gas again pretty soon. But if you pop the car into neutral, you can coast for a LONG way without having to touch the accelerator again for a LONG time.

EPj3, ask yourself who will go farther on a level road...

1. Sam accelerates to and maintains 50 mph for 10 seconds. Then he leaves it in gear and takes foot off the gas. Engine and transmission quicly stop the car.

2. Dave accelerates to and maintains 50 mph for 10 seconds. Then Dave puts car in neutral and takes foot off the gas, coasting to a stop.

Of course, Dave will go a lot farther than Sam! And if they're on a slight downhill, then Dave could go more than TWICE as far as Sam while using a negilgible amount of additional gas. Another way to look at it is that if they each did their characteristic stop-and-go driving on a 10 mile circuit, Dave would spend more time coasting, and less time maintaining 50 mph than Sam. So while Sam will finish the loop faster, Dave will use less gas.

The moral of this story is that the best way to save gas is to learn to manage your car's kinetic and potential energy as efficiently as possible. And coasting (in neutral) can really help to conserve both kinetic and potential energy, but to take advantage of it, you have to learn to look way ahead and anticipate the road and traffic, rather than just reacting to what's a few yards ahead.