The fuel mileage on my 240 D (1983) drops off fairly significantly in the winter. (From 350 miles per tank to just over 300). I have a new thermostat in the car and it warms up quickly and produces very good heat. I am also using synthetic oil, 5W50 to insure easy cold weather starts. However, I notice driving around that diesel trucks and buses cover their radiator grill in the winter. I assume this is to allow them to operate at a higher temperature and therefore more efficiently. I wonder if this would help my 240D. It would be quite easy to make a cardboard or plastic shield to go behind the grill and in front of the radiator. ( I have had to do this before when my thermostat has gone out.) I remember a friend of mine who had an old Peugeot that came with a vinyl cover for the radiator grill. Surely covering the radiator serves some purpose other than deleting excess radiator space since the diesel trucks and buses all do it and have thermostats. Any thoughts?

Darryn
240D - 130K

i remember a previous thread that someone suggested to cover the oil cooler.

btw, i also had a peugeot that came with the shield you mentioned but i only used it when it was below 10deg f ambient temperature.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

Thanks for the repy, I found that thread which I did not find in my prior search looking for "Radiator" instead of "oil cooler." I believe there is also a thermostat built in for the oil cooler. It seems logical to me that covering the oil cooler is not going to have a big impact on the viscosity of multi-viscosity oil which should maintain a viscosity over the range of operating temperatures.

Darryn

Winterized fuel contains fewer BTU's per gallon and the milage drop you are experiencing is almost perfectly in correlation mathematically to the lower energy of winterized fuel (~10%).

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

darryn,
yes i also get that impression after reading some more threads and that the oil cooler is only in operation in the summer heat.


as golden rule was saying the winterized fuel has a big impact on fuel mileage. i also notice the drop in mpg instantly when it hits my tank.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

Last tank my milage dropped to 28 from about 32.5. I have not changed anything or my driving habits. I sure hope it is because of 'winter' fuel and not my dear benz.

thebern

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1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs

My understanding is that by blocking off part of the grill you decrease the amount of cold air hitting the radiator. Hence, you reach "operating" temp sooner in cold weather and, therefore, you get cabin heat quicker?

I've heard, though, that you don't want to block off the fan. Therefore I cut 2 pieces of corrugated cardboard and wedged them in between the top and bottom of the grill on the inside, on either side of the fan.

I think that it does indeed help the car warm up faster, but I cannot be sure.

bern,
yeah i think i'm losing about 4 mpg as well on the average.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

I loose about 2-4 mpg on winterized fuel. I also noticed that the thermostat does not come on at all as long as the heater is "on". That's why I had two nasty surprises in the spring when the temp hit 70F and I found out that my fan switch did not work.

BTW- I complained how my 77hp 2-ton 201 is slow with 0-60mph in 17.6 seconds. I just found out that 3/4 ton 2002 Jetta TDi with a 95 hp diesel does 0-60 in 14.0 seconds. I stopped complaining.

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1985 190D 2.2l Sold-to Brother-in-law
1996 Mustang 3.8l -"thinks it's a sports car"
1988 Grand Wagoneer - Sold (good home)
1995 Grand Cherokee Ltd -"What was I thinking??!!"

I filled up today and got 24 mpg. This I know is in part to Diesel #1 (winter formula), and also my increased ammount of idling now that it's cold.

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1984 190D 2.2 Auto 220k
2001 Jeep Cherokee Sport 70K
2004 Lexus RX-330 ??K
2005 Chrylser Crossfire LTD 6K

Play guitar? Go to www.cyberfret.com for free online lessons!

I used a large piece of cardboard to cover my whole raditor, but didn't cover my oil cooler. Heat, warm-up,and engine temp all were normal for the winter. I had fair heat until I did this. With the fuel changes and the extra idling...we all lose milage in the winter...except you guy's that don't have a winter.

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1983 300SD 343K everyday car
1983 300SD 285K from junk yard-tooks parts from deer car- runs great. Brothers car.
1984 300SD parts car-Hit deer
1979 300D 175K non-turbo "Doctor"
1979 300d parts car

Dlduchon, switching fuel and idling are the reasons for the mileage drop. Look again at those winter fronts on the trucks and you'll notice something: Most newer winter fronts have a hole in the center. Keeps some air moving (parts of the engine, like exhaust manifolds, are air cooled) and located in front of the center of the fan (keeps a balanced load on the shaft bearings). I use a paper beer or soda case because it's already painted. Cut out to fit and attach with 20ga solid core electric wire so that the twist is inside the hood. Easy, fast, and cheap. Some oil coolers have thermostats, some don't. If you need a winter front for the radiator then it won't hurt anything if the oil cooler is covered.

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daBenz - 1970 220D

Some new BMWs have grills that open and close like venetian blinds according to needed intake air flow. Reason is for improved fuel efficiency. Closed blinds force more air over the aerodynamics of the surface of the car, whereas open blinds allow air into the engine bay, acting more like a parachute.

So cardboard in front of your rad may just improve your mileage.

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Cheers!
Scott McPhee

1987 300D