45 mpg W124 300D - it's in the math
 

http://www.fuel-saver.org/Thread-1987-Mercedes-300D-Turbodiesel-40-MPG

Sixto
87 300D

Last post on the page sums up my thoughts exactly. I fail to see how those modifications significantly increase mileage as listed. I am a firm believer in "driving style" modifications for mpgs, but if there is a consistent driving pattern I don't think that guy is fully accurate.

Well . . . larger tires, is about the same as lower the rear diff ratio, so IF he runs lots of highway, I could see a gain in mpg.

I agree driving style is probably the biggest factor . . . when I was driving OTR (Over The Road) semi trucks, started back in 92, industry norms were about 5 mpg running 80,000 pounds around the country, the company I worked for offered a $0.01 bonus if we broke 6mpg! I consisantly got the fuel bonus and most of the drivers couldn't because they always had the foot on the floor (we ran 325 hp gov @65 mph) patience, planning ahead, and only idling overnight if it was extreme temps, as we got newer trucks an d more powerful engines (350 hp!) I was always over 7mph, and hit as high as 11 mph one trip! (mostly level running, and I was not in a hurry and kept it at 55 mph with a light load, no idle at night)

I bought a ScanGaugeII for my gmc pu, it plugs into the OBDII port, and gives you instant read outs, it "Teaches You To Drive" effeciently! same as any car with a instant mpg gauge, watch that and you will see you are letting off the go pedal as you go up the hill to keep the mpg high!

Back in the late 80's I had a 81 Caddy Deville w/4100 motor 8cyl, Normally on my way to work in the next town over I had to go over this one hill about 1 mile from where I lived . . . I noticed that if I maintained 50 mph (the speed limit) I would drop to about 11 mpg! One day I had to come back into my home town in the middle of the day, and then go back to work, once the car was warmed up I climbed that same hill going the same direction keeping it at the same speed I got 18 mpg! (warm engine, tranny, wheel bearings . . .)

Larger tires would reduce fuel economy since you have more rotating mass. Although I don't see how upsizing a bit will affect anything, the change would probably be somethign like 32.659 vs 32.543. But I know on my old SDL going from the stock wheels and tires to the larger ones cost me about 1mpg.


Increasing fuel pressure to the IP won't do much, it doesn't care. The nozzels are still going to get the same pressure. So not sure why the fuel system needed to be hacked.

I'm going to call BS. I think its a light foot, going slow on a nice flat road, and some number fudging.

Funny you came across this at the same time I did. Did you get it from that 87 wagon on Ebay? The guy selling it said something like "it gets just over 30 now, but it's capable of 40!!!" Yeah, like anyone is going to gain 10 mpg just like that. Ha!
Do you know who started that thread on there?? He is from here..maybe that's why it isn't posted here :D;) I won't rat him out though.

Yeah if you took out all the seats, gutted it, limited the throttle/fuel delivery and didn't mind taking 5 minutes 0-60, most cars are capable of 40mpg :D. Maybe you could cut off the roof to lighten it up, then you'd have a custom 87 wagon convertible!

I think those refering to the person going by the fuel gage are on track. I know on both my Ford Contours, I'll have 100 miles from fillup till the needle hits the Full mark. I have had 250 miles on the trip OD at 1/2 a tank. It really drops from there. The last 1/4 drops fast. I think the best I got out of a tank was a little over 400 miles. I only go be filling up the tank full, driving the miles, then filling up the tank full again to see how much fuel was used.
Tom

Especially if people fill it until the can see the fuel, vs. when it shuts off..That will make the first 1/4 last a little bit longer that the others. So yeah, in his case, 150-180 miles might seem like a lot, but geez, the percentage of error with only 4 gallons is really high. Plus, who would brag about something if they haven't even filled up yet? This is why I rarely believe what people who drive hybrids or other small cars say when they boast about getting 8+ mpg more than they should.

My gauage is pretty accurate..the last 1/4 can be a little finnicky sometimes, but that reserve light is always dead on 16 gallons. I have never seen my mileage come out to what I "think" it is when I fill up..usually .5-1 mpg less. However, waiting til the bottom of the tank does make it pretty accurate.

HHO generator.. haaaaa

Retmil is a member here

If you went to physically larger wheels and tires, then your speedometer would have been off by a little bit, as you reduced the final drive ratio. That would account for your "loss" of 1mpg. Once a mass is rotating, it takes very little energy to keep it doing so. Most of the energy a car uses is fighting rolling resistance of the tires, air resistance, and the energy required to keep the physical mass of the car at a given speed....the size of the wheels really has nothing to do with it.

Yeah I know that.

Same diameter, but with a more weight and width. Wider tires take more effort to turn and will hurt you a bit. Thats why eco cars have skinny little things.

Tire tread makes a difference too. If I put more aggressive off road tires on my truck I'll lose a bit.

I think he's saying bigger wheels and tires = heavier. So it requires more energy to accelerate and decelerate. However, I would think that the tire tread and compound would have much more to do with mpgs since they actually determine how much friction is generated between the car and road.

Now that its mentioned, I think I saw a commercial a few days ago for a tire that was supposed to save 1000 miles worth of gas over the lifetime of the tire (another "stretch" calculation if you ask me)...makes me wonder how well it actually performs, especially in wet and emergency conditions where the contact area/friction really matter.

Well I've gotten 1200 miles on one gal. diesel fuel.

Yep; I believe he's the guy who lost his 300D in a crash and bought Babymog's. I wonder how it is treating him!

Yeah, I've seen those too..I think Michelins?
I bought General Ultimax HPs, for numerous reasons, but one being that they had a very low rev/mile rating compared to other tires. I don't know if they are "officially" LRR, however. One thing I did notice, though, is that a lot of these fuel saver tires are not very good at doing anything else. Mine at least had good wet and snow ratings!

The width definately makes some difference. I think the lowest .cd for the w124 was achieved with like..185/15s or something crazy like that. I realize that isn't much different than 195s, but when you start getting into wide-rimmed 265 and whatnot, that must mess with the frontal area a bit.