(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.