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Replacing a gas engine with a diesel engine in a Mercedes

I own a 1972 Mercedes 280SEL 4.5. I would like to replace the current engine with a diesel engine from a 240D or 300D and a conversion kit which allows my automobile to run on vegetable oil. Is this doable.

What does the Forum usually say when these type of questions are asked? I think it is along the lines of “anything is doable if you want to spend enough money”

Why don’t people ask “Is this an efficient use of my money”?

Just sell it and buy a diesel. Not worth the huge $$ for this type of conversion, unless you are a huge DIY mechanic. If you were, of course you wouldn’t be asking here…

And are you wanting to use biodiesel, or make your own, or use vegetable oil/used fry fat/etc? Lots of options.

Yea, it can be done, but unless all the labor is free, I would not recommend it.

People may not ask; “Is this an efficient use of my money/” because the cost is irrelevant. The automobile is of personal value and I would like to keep it but I am also concerned about the environment.

Sell the car and buy an older Volkswagen diesel. Those convert easily to biodiesel, and are quite reliable.

I’m at a loss what status you are seeking with an expensive sports car that smells like Macdonalds at 11pm on Saturday, and won’t outperform an econobox Toyota.

As others point out, the upkeep of a 1972 Mercedes costs an arm and a leg. Whatever you save by using biodiesel will be absorbed many times by the cost of keeping this conversion running. You must have a lot of time on your hands.

The automobile is of special sentiment to our family but I am also concerned about the environment and would like to adapt this machine. I am interested in using vegetable oil.

Yes, it’s doable. The only question would be if you’re willing to spend money to do it.
If you plan on having someone else do this for you then get the wheelbarrow tire aired up and head to the bank first.
Projects like this usually involve one thing after the other and those 100 little nickle and dime things can add up to a sizeable chunk.

If the car needs an engine I’d drop a small block Ford or Chevy in it along with the matching transmission. It would be much cheaper.

Thank you, Mr. Meehan . . . I truly appreciate your straight forward response.

I have no desire to portray a status symbol. I have a machine that is of personal sentiment ans I wish to convert it due to environmental concerns,

Thank you. My car runs fine, I read about the conversion and am just seeking advice. Yours is greatly appreciated.

In that case, do nothing, keep the Mercedes well maintained, and buy an econobox such as the new Ford Fiesta or Mazda 2, both of which are very kind to the environment. You can drive the Mercedes on the weekend on regular gas. The conversion will cause you a lot of headaches, and will certainly spoil a good sports car.

A guy in my neighborhood has a 1976 Volkswagen Rabbit which his father left him. He wisely keeps it in the garage and drives it sparingly. The family car (he has no children) is a Toyota Corolla.

A friend in town here has a 1972 Mercedes 450, just like yours, which his wife can no longer drive. It’s in great shape (only 80,000 miles), maintained by the local dealer, and I advised to sell it to a deserving collector who will take good care of it during its remaining life.

Should such a conversion be properly made you would have to collect and filter used vegetable oil- a quite messy business and have separate fuel tanks on the car with all the necessary plumbing and valves. The car would have to be started on reg. diesel and switched over to the vegetable oil while running, then switched back early enough to use up all the veg. oil in the lines before shutting down. I don’t know how well the car would run as Mercedes owners of this vintage were cautioned not to use regular truck diesel in the winter but use # 3 diesel. (more akin to kerosene or jet fuel)

You’re welcome. I’m not trying to be a naysayer but I’ve done enough engine swaps and modifications to know that Murphy’s Law is always looking over the shoulder when you’re deviating from the norm.

Wire modification here, bracket mod there, adapt this and that, and it can get pretty time consuming.

Thank you. My 280 is currently registered with vintage plates, so I drive it less than 1500 miles per year. I appreciate your point of keeping it well maintained (I get my high-priced tuneups at my local Mercedes dealer). I recently read an article by an owner who completed the engine transition and wanted a second opinion. Your advice has helped me a great deal.

If you have enough money, you can do ANYTHING…By the time you actually have a drivable conversion, you will have spent a TON of money…

We have unlimited funds for this project.

“but I am also concerned about the environment.” Sticking an old 300D Benz motor in an equally old chassis has a NEGATIVE environmental impact, not positive.

If your are “concerned about the environment” buy a Prius, Leaf or Volt and run the Benz’s through a shredder…

Caddyman’s right, old diesel engines are just about the most polluting thing to use in a car. Clouds of soot will follow you…

Vegetable oil is not bio-diesel. And in an old diesel engine such as this you probably can’t even run it on bio-diesel. The manufacturers of todays modern diesel engines don’t recommend anything over B20 or a 20% bio-diesel. And this is a refined fuel.

Vegetable oil contains amino acids. And if you run this in that old diesel engine the acids will attack the fuel system components. The fuel system components were never designed to be exposed to any sort of acid.

I know of two people who tried to run veggie oil in their diesel engines. And all they ended up with was the expensive replacement of the fuel system components.