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1987 Mercedes 300D Turbodiesel - 40 MPG
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RHDZMBZ55 Offline
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Post: #21
RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
(06-12-2008 11:20 PM)retmil46 Wrote:  This car was originally rated 25/30 by the EPA, under the new formula 22/27. Top speed of 125 mph from the factory, it was the fastest production diesel car in the world when new.

Acquired her 2 years ago used, in need of a good bit of TLC at 132K miles.

Prior to April this year, my maintenance efforts were devoted more toward reliability - oil and fuel leaks, new shocks and struts, brakes and rotors, etc. At that time she was knocking down 30 mpg combined.

In April, the tranny was pulled for seal replacement (leaking 1 quart every two weeks). At the same time, the flex discs and center support bearing for the driveshaft were replaced, and the throttle and tranny control linkages were adjusted per the FSM.

End result of this was an increase of 5 mpg, up to 35 mpg combined.

Recent additions were a water vapor injection bubbler jar in the CCV line, going from 195/65R15 to 205/70R15 tires (1 1/4" larger diameter), replumbing the supply to the fuel pump, and adjusting the doseage of my fuel additive.

This week, bubbler jar is running plain water with no heat. Fuel pump supply replumbing resulted in 1 1/2 psi increase in pressure to the injection pump. I had been adding 1 oz/gallon TC-W3 2 stroke engine oil to the fuel, increased this to 2 oz/gallon this tank. Larger tires cause the odometer to read 5% low, and the speedometer to read 1 mph low for every 20 mph - I run at 52 indicated for 55 mph, engine speed reduced by 200 to 300 rpm.

Refilled the tank this past Sunday once these final four mods were in place. Full mark to 3/4 tank is 4 gallons. So far commuting to work this week, for 160 miles actual, fuel gauge is still above 3/4 tank with daylight between the needle and the mark - less than 4 gallons used for 160 miles.

Previous best to 3/4 tank was 140 miles, refilling after 200 miles for the week hand calculated to 35 mpg average for the tank. With 160 miles and still some to spare before the 3/4 mark, this is pointing so far to a 40 mpg average for this tank.

This isn't out of line with what I've heard - that when new, with MB's original attempt at a trap oxidizer (ie, cat) gutted out, these cars would achieve 38 mpg highway with stock tires.

And I've yet to pull and service those 20 year old injectors with new nozzles, or install an HHO generator.

This 20 year old mechanically injected diesel is bloody near getting what a Honda Civic Hybrid is capable of.


CAN YOU EXPLAIN IN MORE DETAIL HOW YOU INSTALLED THE WATER BUBBLER AND REFIT FUEL LIKE, I HAVE A 87 TURBO DIESEL WITH THE SAME TIRES AND WOULD LIKE TO INCREASE MILEAGE ALSO. THANKS.
(This post was last modified: 03-16-2015 03:29 PM by RHDZMBZ55.)
03-16-2015 03:27 PM
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oldbeaver Offline
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Post: #22
RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
   
(06-12-2008 11:20 PM)retmil46 Wrote:  This car was originally rated 25/30 by the EPA, under the new formula 22/27. Top speed of 125 mph from the factory, it was the fastest production diesel car in the world when new.

Acquired her 2 years ago used, in need of a good bit of TLC at 132K miles.

Prior to April this year, my maintenance efforts were devoted more toward reliability - oil and fuel leaks, new shocks and struts, brakes and rotors, etc. At that time she was knocking down 30 mpg combined.

In April, the tranny was pulled for seal replacement (leaking 1 quart every two weeks). At the same time, the flex discs and center support bearing for the driveshaft were replaced, and the throttle and tranny control linkages were adjusted per the FSM.

End result of this was an increase of 5 mpg, up to 35 mpg combined.

Recent additions were a water vapor injection bubbler jar in the CCV line, going from 195/65R15 to 205/70R15 tires (1 1/4" larger diameter), replumbing the supply to the fuel pump, and adjusting the doseage of my fuel additive.

This week, bubbler jar is running plain water with no heat. Fuel pump supply replumbing resulted in 1 1/2 psi increase in pressure to the injection pump. I had been adding 1 oz/gallon TC-W3 2 stroke engine oil to the fuel, increased this to 2 oz/gallon this tank. Larger tires cause the odometer to read 5% low, and the speedometer to read 1 mph low for every 20 mph - I run at 52 indicated for 55 mph, engine speed reduced by 200 to 300 rpm.

Refilled the tank this past Sunday once these final four mods were in place. Full mark to 3/4 tank is 4 gallons. So far commuting to work this week, for 160 miles actual, fuel gauge is still above 3/4 tank with daylight between the needle and the mark - less than 4 gallons used for 160 miles.

Previous best to 3/4 tank was 140 miles, refilling after 200 miles for the week hand calculated to 35 mpg average for the tank. With 160 miles and still some to spare before the 3/4 mark, this is pointing so far to a 40 mpg average for this tank.

This isn't out of line with what I've heard - that when new, with MB's original attempt at a trap oxidizer (ie, cat) gutted out, these cars would achieve 38 mpg highway with stock tires.

And I've yet to pull and service those 20 year old injectors with new nozzles, or install an HHO generator.

This 20 year old mechanically injected diesel is bloody near getting what a Honda Civic Hybrid is capable of.

I think you are not measuring accurately your fuel economy. First of all, you should measure a complete tank to be valid. 160 miles or 180 miles is not valid. You need to top tank to make a valid measure.

I have a very neat 1993 Mercedes 300D turbo and my best tank on road is 13.2 km/l which is about 31 mpg. It is physically impossible to get 40 mpg with this car on a full tank. Of course if you drive downslope cornering you can improve that, but this would be teasing yourself.

My car is getting more than a new car according to EPA, having 260.000 km on it. Well aligned, balanced, nice engine and trans, good turbo and good engine.

Try the following: top the tank and drive until you cover 800km. Then top again and write down the liters of diesel.

Best mileage,

Oldbeaver
(This post was last modified: 04-11-2015 07:50 PM by oldbeaver.)
04-11-2015 07:48 PM
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Doctor J Offline
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Post: #23
RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
I agree that the true way to test your fuel economy is to fill up and then divide the miles on your trip meter. by the gallons on the pump.. I have recently purchased a 91 300d and I came across this thread while looking for info. My 91 has some work that needs to be done to its vac system amongst other things. it has about 250k on it. at first I was getting about 25-26 mpg. after replacing the injectors i now get 30+mpg. My mechanic says the car will get 37 once everything is up to snuff. I do live in the hills outside of town and i know that that plays a large part in the economy.

I recently filled up and i had gotten 28+ mpg on my previous tank, I hit the hwy and went to my friends new house over and hour away one direction. I used cruise control and stayed driving 5 or so miles over the speed limit as most mericans do.

When I came back to town I was in disbelief when I looked at my fuel guage, I had clocked 104 miles on my trip meter, ...so I went back to my biofuel statition and filled her up, to the brim and then some just to be sure. First the pump said 2.05 gallons! And after squeezing another little squirt until the pump would not let any more fuel out the pump read 2.15 gallons.... [undefined=undefined][undefined=undefined]so I did indeed get 48.37209302 miles per a gallon![/undefined][/undefined] I even stopped on the way back to get some data for my phone as I use a prepay plan...so the economy may have even been better.

There is nothing anyone can say to deny this fact. I filled at the same exact pump at the same station, and I really squeezed the last possible bit of fuel into the tank. it was on the verge of overflowing. So by my real life experience of 48+ mpg, someone else getting 40+ is truly possible.

I filled up today and I had 474 miles on my trip meter and it took 15.749 gallons to fill. So diving up and down hills and my very steep gravel driveway is indeed keeping me at 30 mpg.
05-22-2015 10:37 PM
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