300 SD or SDL - Which is Better, and Why?
 

This is a great community of enthusiasts! I've already gained much knowledge over just the last few days. Thanks to all who have helped so far.

I'm currently looking for my first Mercedes and just found out that the 3.0 L diesel engine comes in both 5 and 6-cylinder flavors! I was originally looking for an early to mid-eighties 300 SD, but now I'm wondering if I shouldn't move up the evolutionary ladder a rung or two.

I understand that the 6-cyl. is stronger, but can anyone quantify that for me in terms of power rating, acceleration times or just seat of the pants feel?

How would you describe the difference in power - torquier, more top-end power, better mid-range...?

Could I get your opinion as to which is better, and why?

Were there any major design changes, or did they just reduce the size of the pistons, add a cylinder and change the crank?

How do they both compare in terms of longevity/reliability?

What are the strong and weak points of each powerplant.

I've heard that the 3.5L 6-cyl. engine is one to definitely stay
away from. Does the 3.0L version share any of the same problems?

I prefer to do most of my own basic (and sometimes not so basic) maintenance. Are both engines equally easy to work on? Any caveats?

Thanks again for your help

Gary

This is a fairly popular topic so do a search for further info.

The 6 cyl also has an aluminium head susceptible to overheating, other then that its apparently quite durable.

Aside from the power, the 6 is also quieter and smoother.

I am faced with the same choice and I think I will go for the iron-head 5 cyl, If i had a bit more $$ to spend, I think id get the SDL.

I own them both
 

The six has way more top end power. It is smoother and quieter at highway speeds. It has very little low end accelleration and is not at all fun to drive around the town (SF) in. The first owner of mine cracked the head, so hopefully that repair is out of the way.

The five is simpler to work on for sure. It also seems like it has a better engine/powertrain for around town. It humms nicely on the highway.

In either case, it really depends on the individual specimen. They are both excellent vehicles.

later

I think the SDL is superior to the SD. Mine has over 270K on it, and never had the head off. The last two oil changes, I found that my car consumed ZERO oil on 3,000 and 3,500 miles.

The acceleration, midrange and top-end are all superior to the 5 cyl.

It is true that you should watch the temperature and keep the cooling system healthy, but this is the case with every car.

I think it is just a seperior car all around, its newer style 126 with an airbag and ABS. IMO, it also rides and handles better than the 81-85 126 cars.

I just bought a 1987 300SDL and really like it. I don't have the technical knowledge on these cars that a lot of folks here have, but I can agree on several of the comments.

- Highway cruising is a real strong point of this car. I bought her down in Salt Lake and drove her up to Seattle. At 75 mph she is so quiet it is almost erie. A very easy car to drive on the highway for hours on end.

- In town she does start slow, but watch out when the turbo starts to spool. She accelerates hard and smooth after about 2,000 rpm.

- Lots of room. The 300 SDL is HUGE inside. She is actually my wife's car and my wife carries our two kids in it. There is enough room on the floor in the back to store every toy they can even think to bring and still have room to spare. For all this size she handles really nicely around parking lots and small streets.

- To add to the room issue, I am 6' 2" and when I drive the seat is all the way back. I have tried sitting in the back when I have the seat all the way back and my knees are a good 6" from the front seat.

Engine types aside, the 300 SDL is a magnificent car. Well worth considering.

Bill:

Just by an 82-85 300SD or SDL (both available) -- the 603 was used in the 86 and later 300S series.

I don't have any personal experience with the 617 turbo, but the 603 in both my brother's SDL and my 300D has plenty of power -- takeoff is about the same as the non-turbo 300 (that is, a bit slow), but man, the push when the turbo comes up!

The 617 turns out about 125 hp as I remember, and the 603 is good for 145 -- don't know the torque for the 617, but the 603 is 195 ft/lbs.

The 603 definitely moves the SDL along nicely.

Peter

This is incorrect. You could not buy a 300SDL 5cyl in 1981 to 1985. The 300SDL 6cyl came out in 1986 and ended in a 1987.

I would strongly urge you to have a PPI (pre-purchase inspection) done before spending your hard-earned money. Unless you are mechanically proficient and the owner will let you inspect the car before purchasing it, a PPI should find defects that may not be obvious to you. A member living in your area may be able to recommend a good shop to do a PPI or look in the Forum section about shops to find a good one in your area.

Good Luck!
Tom

We love the back seat room of the SDL! With the aft facing baby seat we still have a good 6-8 inches additional clearance between the front seats and the front edge of the baby seats. Aft facing baby seats don't fit in a 190D or 3 series BMW without the driver eating the steering wheel and the front passenger in the glove box.
The SDL is within 6 inches as long as our 94 Suburban. But the SDL drives like a mid-size car in the parking lot as compare to the "bus-like" turning radius of the Suburban.
It's as quick as most econ cars up to 25mph. By 35 it pulls away from the econo's. At highway speeds it's great. Not quick, but continues to pull. Pulls past 100mph without a problem at all. I had mine up to 118mph and it would have keeped going. Feels the same at 110mph as it does at 55mph.
Very comfortable x-country car! I drove mine for 18 hours in one day from eastern CO to Portland OR. It nice having 550+ mile range on a tank.

284,000 miles, original head, original trans
no oil consumption between 2500 mile changes.

I'd own an older 5 cylinder too if I had room!

good luck

2500 mile changes, huh? I feel guilty now, I'm at 3500 miles and waiting for the oil filters to arrive. I change every 3000.

272k and going strong!

Thanks to All
 

Thanks to all of you for your opinons and suggestions - very helpful!

This is great forum!!

Gary

My SDL runs great, SD is a super car as well, but I am glad I waited for the SDL!

There is a difference between an 86 300 SDL and an 87 300 SDL.

The 86 (except CA.) came without an oxidizer and all 87s came with them installed.

There are some folks that believe that over temp possibilities were greater with oxidizers, than without. So, given a choice, the 86 may provide less (small) of a chance of getting a car with a cracked head.

Does anyone know of an 86 cracked head problem?

Harry
86 300 SDL
85 300D Euro

The SDL is a cut above the SD for sure but if you've spent any time under the hood of an SD, you'll wonder why you got the SDL. The encapsulation panels are a nice luxury touch until you drop a tool or fastener and it doesn't hit the ground. Even things you do once in 10 years such as replacing glow plugs take so much longer to do in the SDL.

What you save with the SDL for not having to adjust valves you'll give back in having to replace the $250 vacuum pump every 100-150K miles.

It impresses me that there isn't a bigger fuel mileage penalty to pay with the SDL over the SD.

Sixto
91 300SE
87 300SDL
81 300SD (sold... shoulda sold the SE)

Sorry, I forgot the W126 came out before 82!

I also thought the only difference between the SD and the SDL was the 6" or so stretch in the rear floor pan -- I was under the impression that everything else was the same.

Peter