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1987 Mercedes 300D Turbodiesel - 40 MPG
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retmil46 Offline
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1987 Mercedes 300D Turbodiesel - 40 MPG
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.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
06-12-2008 11:20 PM
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Hoyt7811 Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
Sounds great. Can you please explain what a "CCV" line means? I have an old 300sd and would love to add one of those bubblers.
Thanks
06-13-2008 02:59 AM
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retmil46 Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
Hoyt7811 Wrote:Sounds great. Can you please explain what a "CCV" line means? I have an old 300sd and would love to add one of those bubblers.
Thanks

CCV = Crankcase Vent, the hose running from the valve cover to the air intake, recycles all the blowby gases (and oil vapor) that get past the cylinder and valve seals back to the intake to be "recycled" thru the engine. Essentially the same as the PCV (Positive Crankcase Ventilation) hose on a gas engine, except for the fact since our diesels don't pull a vacuum on the intake manifold, there's no check valve/restrictor in the valve cover - just a simple hose between two points.

One caveat - there is a LOT of oil vapor that gets carried over with the blowby gases. My bubbler jar is installed downstream of a Mann and Hummel Provent 200 CCV filter which strips out most of the oil vapor. These are filters made specifically to be installed in the CCV lines on upwards of 500 HP diesels, to strip out the oil vapor and keep it from being sucked into the intake manifold, where it can combine with soot to form hard gummy deposits that can choke off the air intake.

If you just install a bubbler jar in the CCV line, without some type of oil vapor filter arrangement ahead of it, your bubbler jar will end up condensing out all this oil vapor - you'll end up with an oily gooey mess inside the bubbler jar that won't evaporate much water.

Two places you can buy Provent 200 filters are Reliable Industries and Air Now Supply, should pop right up on a Google search. Also check out the forums on http://www.tdiclub.com for discussion on Provent filters - the VW TDI crowd are big believers in CCV filters.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
06-13-2008 07:50 AM
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retmil46 Offline
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Update - '87 MB 300D - 45 MPG
I stand corrected on my fuel mileage estimate - it took another 20 miles, an additional leg into work - for a total of 180 miles - before the fuel gauge dropped to the 3/4 mark.

That works out to an estimated 45 MPG!!!Shocked

I actually had two of my coworkers come out to the vehicle last night after shift to verify the odometer and fuel gauge readings so that I had witnesses.

To say that I was quite pleased would be an understatement of the first magnitude.

I'm still trying to wrap my head around how the four mods I listed in the original post could result in nearly a 10 mpg increase, especially when it was already getting well above average fuel economy.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
06-14-2008 07:12 AM
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Hoyt7811 Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
Thanks for the info, I'll look into it. BTW, what is the purpose of the 2 stroke oil added to the fuel? Just more lube? And at 2oz/ gallon?
Thanks
Hoyt
06-16-2008 03:11 AM
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retmil46 Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
Hoyt7811 Wrote:Thanks for the info, I'll look into it. BTW, what is the purpose of the 2 stroke oil added to the fuel? Just more lube? And at 2oz/ gallon?
Thanks
Hoyt

Exactly - lubrication for the injection pump and other components that are lubed/cooled by fuel.

Been more than one report I've seen that the fuel distributors aren't consistent with the lubrication additives they're supposed to be adding to ULSD, to make up for the loss of lubrication factors when the fuel is processed to remove the sulfur.

Over on Turbo Diesel Register (Dodge Cummins crowd), they actually did a controlled study of different fuel additives to see which was best at lubrication and reducing wear. Suprisingly, just plain 2 stroke engine oil - they used 1 oz/gallon - was in the top five for effectiveness, beating out Power Service and Stanadyne by a long shot. And at $8/gallon at Wally World, one of the most cost-effective as well.

I'm beginning to believe I inadvertently "steam cleaned" the inside of the engine. For 3 weeks, I was running 30% methanol washer fluid in my bubbler jar, heated up to around 130 F to enhance evaporation by a coolant heater I fabricated (tapping off of the heater hose with a throttle valve to control flow and temp). It would suck down nearly a quart of fluid in a week - 200 miles - and I believe this hot methanol/water vapor acted to clean out the carbon and other deposits. Then, once I switched back to plain water with no heat - such that the engine was getting much cooler intake air along with the water vapor - all the other factors were in place such that the mileage simply soared by 10 mpg.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
06-16-2008 10:38 AM
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OM617 Offline
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Post: #7
RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
40mpg isn't physically possible in a 300D, even with the TrapOx gutted. A 190D 2.2 with a 5-speed manual will barely reach that, let alone a 300D with an extra 2 cylinders, a turbo, 800lbs extra weight and worse aerodynamics.

I suggest you get something like a G-TECH/Pro and verify your odometer accuracy.
05-11-2009 02:59 PM
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hellspcangel911 Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
(05-11-2009 02:59 PM)OM617 Wrote:  40mpg isn't physically possible in a 300D, even with the TrapOx gutted. A 190D 2.2 with a 5-speed manual will barely reach that, let alone a 300D with an extra 2 cylinders, a turbo, 800lbs extra weight and worse aerodynamics.

I suggest you get something like a G-TECH/Pro and verify your odometer accuracy.

I understand your skepticism and partially agree, but I have owned three 1987 300TD wagons, and all of them have gotten over 32mpg during my regular driving. Even when the car had 470,000miles on it (finally sold it at 492k) it was still getting over 30mpg. My grey one now is getting over 42mpg but thats because of a few tricks with the waste gate, injecors, tighter transmission shifting and differential.
Mind you, these have the 603 engines 6cyl 3.0 Turbo Diesel, so they aren’t exactly the same as the 300D, but his numbers are realistic. As far as you comparison with the 190D, the 2.2L in it did not have a turbo, but if you look at the 2.5D with the turbo the numbers are much closer. If you do not have a turbo, you aren’t getting 40mpg, please clarify your car specs.
As far as adding two stroke oil, its not needed, the basic composition of diesel, well, it’s a lubricant in itself, the extra oil is just harder on the turbo, cat and muffler by producing more soot.
05-11-2009 08:26 PM
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studebaker Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
(05-11-2009 08:26 PM)hellspcangel911 Wrote:  
(05-11-2009 02:59 PM)OM617 Wrote:  40mpg isn't physically possible in a 300D, even with the TrapOx gutted. A 190D 2.2 with a 5-speed manual will barely reach that, let alone a 300D with an extra 2 cylinders, a turbo, 800lbs extra weight and worse aerodynamics.

I suggest you get something like a G-TECH/Pro and verify your odometer accuracy.

I understand your skepticism and partially agree, but I have owned three 1987 300TD wagons, and all of them have gotten over 32mpg during my regular driving. Even when the car had 470,000miles on it (finally sold it at 492k) it was still getting over 30mpg. My grey one now is getting over 42mpg but thats because of a few tricks with the waste gate, injecors, tighter transmission shifting and differential.
Mind you, these have the 603 engines 6cyl 3.0 Turbo Diesel, so they aren’t exactly the same as the 300D, but his numbers are realistic. As far as you comparison with the 190D, the 2.2L in it did not have a turbo, but if you look at the 2.5D with the turbo the numbers are much closer. If you do not have a turbo, you aren’t getting 40mpg, please clarify your car specs.
As far as adding two stroke oil, its not needed, the basic composition of diesel, well, it’s a lubricant in itself, the extra oil is just harder on the turbo, cat and muffler by producing more soot.

I've driven Mercedes and VW diesels as well. You can not figure mileage accurately using the fuel gage method. It takes several fill ups using the miles divided by gallons used to get any kind of accurate measurement and you still need to verify speedo accuracy for proper measurement. Until then, it's just an optimistic guess.
05-20-2009 02:09 PM
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Night_Sailor Offline
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RE: 1987 Mercedes 300D Turbodiesel - 40 MPG
Your methods of calculating fuel economy are sloppy. It seems to me, you are fudging the numbers on purpose because you want to see higher numbers, rather than accurate numbers. You can't get 40mpg unless you are rolling down hill the whole way.

This is a physics problem. The formula is odometer reading divided by fuel used. When doing a problem such as this, a physics student would also estimate the accuracies of each variable and calculate the accuracy of the answer. You have an answer with a high percentage of error due to your methods.

Lets start with fuel accuracy:

If you don't run the tank down fairly low and top it off each time, your estimates for fuel consumption will be highly inaccurate.

The percentage of error in four gallons is considerable. For example, if you fill you tank up with an extra quart--that represents a 6% error. An extra half gallon is 12% error. A 1 gallon error means you are off 24%.

Consider the error in 20 gallons ( full tank). If you are off a quart--the error is 1.2%; for a half gallon--the error is 2.4%; an extra gallon--the error is 4.8%.

There is a huge error factor when using your method compared to the full tank method--up to 20%.

And this does not account for sensor accuracy and odometer error. You could be off over 30% in your calculations. Which means your numbers are totally meaningless.

Your tank sensor could also be in error to an equivalent degree. Tank sensors are notoriously inaccurate. No one would trust a tank sensor to give accurate measurements. These are roughly accurate at best--dependent on such things as degree of level, motion of the fuel inside, and sensor accuracy.

This is the reason most people do not use the tank sensor at all. They use the standard method of estimating fuel consumption by running out a fully topped off tank, and filling to the same topped off level to get a measured quantity at the pump. Even so people still test the fill amounts over a period of time, because diesels are not run dry--so fill up quantities will vary However, at least the accuracy is improved though repeated research.

If you see the same fuel economy on tank after tank, measured at the pump, you can have some confidence it is accurate with respect to the quantities of fuel used.

There still remains the question, how accurate is your odometer. Tire size is an important factor. Heat changes the dimensions of a tire. Tire diameter is not an accurate method of estimating the circumference of a tire. You have to measure the outside circumference of the original and the new tires to get a meaningful estimate of tire error--also this needs to be done with the tires mounted on the rims at normal pressure with the weight of the car on them. Let me be perfectly clear--you run the measuring tape around the outside of the tire. If you just use the diameter of the tire, and mulitply it by 3.14159 you will be multiplying the error in your diameter measurement. It will be 4 times more accurate to run the tape around the outside of the tire. For one thing, due to the shape of a tire, it is difficult to measure the diameter accurately.

Then there is odometer gearing. These gears can get you close to accurate, but not extremely accurate. So you need to measure this error also. Double check it on the freeway on a long trip using the mile markers. Find out what the adjustment factor is and use that to make distance corrections for a full tank of fuel.

Next time fill up your tank to the absolute top. Run it down to nearly empty--divide the actual mileage by the gallons purchased. That will be a fairly accurate number.

As others have mentioned, this car will not achieve those sorts of numbers. Fuel economy is a function of frictional losses--tire rolling resistance and wind resistance. According to physics, frictional losses are a function of the weight of the vehicle. I've owned many diesels, from small VW Rabbits, to 1 ton pickups. The one single factor, that more than any other, determines fuel economy is the weight of the vehicle.

If you want better fuel economy, you will need to start removing parts of your car to lighten it up. Take off the side view mirrors to improve wind resistance and install camera's. Add a spoiler to the front and back to decrease wind resistance. Lower the car. Repack all your bearings. Change your wheels to lighter ones. Likewise lighter weight tires (easier to turn) and tires with lower rolling resistance will improve fuel economy.

The bottom line is you do not have an accurate method of measuring fuel consumption. You are not even close to being accurate.

Or you could continue deluding yourself that you have magical powers by thinking your method is accurate.
Oh I understand why he is so optimistic about his fuel economy. He is trying to sell the car for $7000.

His starting bid is $4000. Not one bidder. And he won't get one.

I'll offer you $1500 for a 40 mpg car. But I'll only pay you this amount times the actual fuel economy divided by 40. That will work out to $1200--that is my offer $1200, and that is probably too much given all the defects on the car.
(This post was last modified: 07-07-2009 06:02 AM by Night_Sailor.)
07-07-2009 05:45 AM
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