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Always Remembered RIP
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Discussion Starter #1
After looking at several of the 6-cyl SLs I've finaly found a mint, very low mileage 280SL with full dealer history.
However I did originaly want a 300SL mainly for fuel consumpsion so I'm wondering how far apart in terms of Urban/City MPG are the two?

Also more importantly can a '84 280SL run on unleaded fuel and will it be okay with 95 or will I have to use Shell higher Octane Opti-slurp or similar.
 

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Mercedes 300 SL-24
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fuel

That's my big question too: can my 280 run unleaded fuel?
All that I've read until now tells me that unless you have a catalysed engine (KAT, I think?) or a ready to be catalysed (RUF?) engine you can use Pb free fuel. Otherwise you should stik with additivated fuel.
I don't know if in '84 Mercedes already produced both engine types.
Anyway, I always use additivated fuel. The price in Portugal is exactly the same as 98 octanes, only more difficult to get.
Maybe you should ask Mercedes? Sometimes we can't imagine the info they can give and the parts they still have in stock!

Jorge
'81 SLC
 

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Always Remembered RIP
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520 Posts
Discussion Starter #3
Re: fuel

That's my big question too: can my 280 run unleaded fuel?
All that I've read until now tells me that unless you have a catalysed engine (KAT, I think?) or a ready to be catalysed (RUF?) engine you can use Pb free fuel. Otherwise you should stik with additivated fuel.
I don't know if in '84 Mercedes already produced both engine types.
Anyway, I always use additivated fuel. The price in Portugal is exactly the same as 98 octanes, only more difficult to get.
Maybe you should ask Mercedes? Sometimes we can't imagine the info they can give and the parts they still have in stock!

Jorge
'81 SLC

MBUK said my old '82 230CE could safely use 3 tanks of lead to 1 tank of unleaded although I've not yet asked about the 6-cylinders. I've seen a few 0f the '85 280s (just before the 300 launch) with the green Unleaded sticker but I'm not sure whether any modifications were done to the engine?
I must agree with you on how good Mercedes are on spares; I can still get almost any part for my '61 220SEb within a week, and most service items off the shelf[:)].
 

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280SL 1982
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Unleaded fuel

I have already been in contact with MB via their email help line. I gave them my VIN number and the reply was that my 1982 280SL can run on unleaded but at some time in the future it may need new valve seats. They also said that MB did not recommend the use of aftermarket fuel additives or 'lead replacement fuels'. I have been told elsewhere that alloy heads have to have hardened inserts for the valve seats as it is not possible to make a workable valve seat out of the alloy. This is unlike iron cylinder heads where the seat can be machined in the head material.
Also there is the matter of 'lead memory' in the head, where the seat has a coating of lead and this will take some time to disperse when unleaded fuel is used.
So I am running on Shell Optimax without additives and whether the head needs work in the future we shall see. The car has not run for some years before I got it, but on Sat. last I did a round trip of 200+ miles and returned 22 mpg. with which I was quite pleased.
 

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Always Remembered RIP
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Discussion Starter #5
Don't quote me on this; but I would have thought if you set up the tappets and then chec...

Don't quote me on this; but I would have thought if you set up the tappets and then check them again after a few thousand miles this would give you an indication to whether the valve seats are wearing down significantly.

I’ve found an old ’82 280CE technical sheet (same engine, transmission, axle ratio, weight etc.) in the garage and the fuel consumption figures for the automatic are:
Simulated Urban 19.1 mpg
Constant Driving 90 kph (56 mph) 28.7 mpg
Constant Driving 120kph (75 mph) 23.4 mpg
As no doubt you stuck to the the 70mph speed limit[;)] 22 mpg for a 200 mile trip sounds okay.
 

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280SL 1982
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Unleaded fuel

You are right about the valve clearances, if the top end of the engine is affected by the unleaded it will be a gradual process so I will wait and see.
With regard to the fuel consumption, I was pleased as the car has not run properly for several years until I started using it 2 weeks ago. I hope it will improve a little as it runs some more.
Does anyone know the purchase price of a 280SL in 1982?
 

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Mercedes 300 SL-24
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I can tell you the price of my 280 SLC in 1981.
I have the original invoice.
It came wit...


I can tell you the price of my 280 SLC in 1981.
I have the original invoice.
It came with many extras including a/c, 4 power windows, central locking, ABS, automatic gearbox+tempomat, alloy wheels, right side mirror, becker mexico electronic and electric roof. If my memory doesn't fail me the total ammount was around DEM 61000 (it was bought in Germany).

Jorge
'81 280 SLC
 
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