Fuel Economy - Page 2 - PeachParts Mercedes-Benz Forum

ConnClark · #16 03-17-2008, 11:34 AM

Quote:

Originally Posted by imagesinthewind

*Fill the tank at the half way point instead of allowing it to go to empty.

How does this save fuel? This might be a practical method for saving money when fuel prices are rising but it does not save fuel. This is the equivalent of reducing you fuel tank by half and adding dead weight of half a tank of fuel.

To save fuel one would be better off running the tank down near empty and only filling it up half way. That would reduce the extra weight lugged around by the engine.

Quote:

Originally Posted by Dana B.

The first suggests that when stopping, engine fuel flow with the foot off the pedal is affected by the rate of decelleration. This doesn't make sense. The engine should get the same mgp whether you're coasting to a stop, or have locked up the brakes.

Lets do a thought experiment. Imagine a vehicle under conditions where you could duplicate the acceleration up to 55 mph using the exact same amount of fuel with two different runs. Now on each run the engine shuts off as soon as 55mph is reached. On the first run the vehicle has its brakes applied bring it to a prompt stop. On the second run the vehicle is allowed to coast in neutral to a stop. On which run does the vehicle go the furthest distance? Considering both runs used the same amount of fuel the one that traveled the furthest got the best mileage.

tobybul · #17 03-17-2008, 11:59 AM

Avg
Annual ------- Mileage -------
Manufacturer Fuel -estimates- -- Unadj -- Engine Description Drive Transmission Fuel
+________________________
Car Line Cost Cty Hwy Cmb Cty Hwy Cmb Cid/cyl (type) Sys Trans O/d Description Sy T

300d/300cd $ 819 21 22 22 24 28 26 183( 3.0l) / 5(dsl,trbo) Rwd A4 Fi D 4dr- 89/13

300sd $ 819 21 22 22 24 28 26 183( 3.0l) / 5(dsl,trbo) Rwd A4 Fi D 4dr- 94/15

tobybul · #18 03-17-2008, 12:02 PM

Quote:

Originally Posted by t walgamuth

If the're are dragging they should generate heat. Check for that.

Tom W

You will also smell some type of burning odor when you get out of the car after a drive.... thats how much heat a dragging brake will cause.... bad news!!

ConnClark · #19 03-17-2008, 01:58 PM

Quote:

Originally Posted by tobybul

Avg
Annual ------- Mileage -------
Manufacturer Fuel -estimates- -- Unadj -- Engine Description Drive Transmission Fuel
+________________________
Car Line Cost Cty Hwy Cmb Cty Hwy Cmb Cid/cyl (type) Sys Trans O/d Description Sy T

300d/300cd $ 819 21 22 22 24 28 26 183( 3.0l) / 5(dsl,trbo) Rwd A4 Fi D 4dr- 89/13

300sd $ 819 21 22 22 24 28 26 183( 3.0l) / 5(dsl,trbo) Rwd A4 Fi D 4dr- 94/15

I question some of these test results/estimates because I know for a fact that the 300SD gets lower mileage than the 300D or 300CD due to the fact its heavier.

#20 03-17-2008, 02:01 PM

Quote:

Originally Posted by ConnClark

I question some of these test results/estimates because I know for a fact that the 300SD gets lower mileage than the 300D or 300CD due to the fact its heavier.

Except on the highway where it's better aerodynamics means less energy to propel it.

clothmoth · #21 03-17-2008, 02:36 PM

I just bought my '83 300d a couple weeks back so I only speak from a couple tanks of experience here. . . . I have a fairly heavy foot, live in a highly congested area, and regularly spend an hour in traffic each way on my commute but occassionally get a bit of open freeway worked into the mix as well.

My average has been right at 24 mpg with this highway / city mix, not actively trying to conserve gas but not pedal to the metal non-stop either.

Dana B. · #22 03-17-2008, 08:07 PM

Quote:

Originally Posted by ConnClark

Lets do a thought experiment. Imagine a vehicle under conditions where you could duplicate the acceleration up to 55 mph using the exact same amount of fuel with two different runs. Now on each run the engine shuts off as soon as 55mph is reached. On the first run the vehicle has its brakes applied bring it to a prompt stop. On the second run the vehicle is allowed to coast in neutral to a stop. On which run does the vehicle go the furthest distance? Considering both runs used the same amount of fuel the one that traveled the furthest got the best mileage.

Thanks for the comments. I get it. Sooner you get boot off pedal on the way to the stop sign, the sooner fuel isn't injected (in larger spurts) into the cylinders. So it isn't the rate of slowing that saves fuel, but less total time on the go pedal.

argus445 · #23 03-18-2008, 07:50 PM

what difference does fuel level make?

#24 03-18-2008, 07:51 PM

Quote:

Originally Posted by argus445

what difference does fuel level make?

Weight. Diesel is 8lbs/gallon. A 21 gallon tank is 168lbs so 1/2 a tank is only 84lbs.

#25 03-18-2008, 07:52 PM

Quote:

Originally Posted by argus445

what difference does fuel level make?

less fuel = less weight

t walgamuth · #26 03-18-2008, 08:41 PM

Personally I always drive naked to save weight.

Tom W

Brian Carlton · #27 03-18-2008, 08:50 PM

Quote:

Originally Posted by t walgamuth

I never could get as good as 20 in town with mine. And low to mid twenties highway was what I found. High twenties for a turbo motor was never in my experience.....to get that kind of mileage you need to drive 65 highway or less or have a stick conversion.

Tom W

27-28 consistently...........on winter fuel running 65-70!! You just have to know how to drive...........