Driving 1976 240D MB in winter


Does anyone know thae best additives for an

old deisel Mercedes for winter. I heard mixing a gallon of regular gas to each tank. what else to ensure a better start


Make sure all the glow plugs are working.


Mixing gasoline of #1 fuel will help prevent gelling, but that’s not usually an issue unless it’s below 0F, it will not really help with combustion. A cetane booster will help cold starting. I also use 5W40 synthetic oil because the starter will spin the engine considerably faster in the cold. I agree that you need to make sure your glow plugs are in good shape, and you really need a strong battery. Also, have your valves been adjusted recently (they are supposed to be done every 15K miles on your engine)?

Also, do you have a block heater installed (right side of the engine block above and in front of starter)? Some of them have the heater but not the cord installed.

Edit: BTW, don’t even think about using starting fluid in that engine, very bad.


Where is the car? UUper Canada or Florida. it makes a difference.

In either case you should not need to add any gasoline or any other product to the fuel you are buying as long as it is good diesel. It will be formulated for the local weather. The only time you would need any additives due to the cold would be if you fill up down south and make a long drive north, or a sudden and unusually early cold snap. Then you should use a commercial anti-gel product not gasoline.

As noted make sure the glow plugs are full functional. If you are in a cold area some sort of heater (block heater) can be helpful.


A block heater


A block heater is very nice, but shouldn’t really be necessary under “normal” conditions. I’ve started mine at -5F without a block heater after it sat outside at a hotel all night. I do plug mine in at home if it’s going to unusually cold, it’s easier on the engine and having instant heat is nice.


Again, this depends on the region, but if I were you, I probably wouldn’t drive a sweet old benz like that in the winter at all. Pretty much the only thing that can kill an old Benz is rust, and I must say, I see a LOT of rusty old 70’s Benzes-- seems like more the rule than the exception and I don’t live in a particularly rust-prone area. A cruddy 15-20 year old “salt car” would probably be a good investment to keep your benz nice for the next few decades. Otherwise, make sure you get frequent undercarriage rinses if you’re driving in the snow.

As the others have posted, if you have good compression and your glowplugs are in proper working order, the engine will have no trouble with what comes out of the regular old diesel pump.


One other thing you can do is install the newer type (parallel circuit) glow plugs in place of the older loop type (series circuit). These should work better and you won’t lose all the plugs if one fails:


I would also keep it away from any salt, W115 bodies do tend to rust.


The factory does not recommend any fuel additives. Use good fuel from a busy station that winterizes the fuel early. This describes most truck stops. If you do use an additive I’ve seen good luck with Diesel Service products. Diesel Purge, while technically not a fuel additive, has a good track record as well.

As stated above, an upgrade to the new glow plug and relay system is a big help. But the proper operation of the entire system is a must for cold weather starts. A good battery gets the starter spinning fast enough, and properly adjusted valves help ensure good compression. Good glow plugs heat up the chambers and good fresh fuel filters with good winterized fuel running through them are the final factor.
Of course a block heater helps a lot in extreme conditions, but shouldn’t be necessary if everything else is up to snuff and it stays above zero.

Spending some time in the fall preparing a Benz for the cold winter months is time well spent.
Trying to start one in the cold with a weak battery and mis-adjusted valves can be a swine.



Agree that good glow plugs and synthetic oil, together with a good battery will work. I have use block heaters for over 40 years and they reduce engine wear, make starts easier and proglong battery life. A really cold start equals 500 miles of normal driving in terms of engine wear! So use a block heater with a timer to come on 1.5 hours before you start the car. I get 7 years out of a premium battery on a normal gas powered car. Recommend you use the block heater any time below freezing when parking outside.