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Is unleaded OK

Started by Tomi, 02 February 2006, 06:46 AM

Tomi

Hello fellows,

we have a debate here in Finland about the need of leaded fuel for old MB engines. Some say that at least a fuel additive is needed to protect the valve seats and guides. Some fuel stations here also say so. I'm speakink of engines M102, M110 and M117 from 75-85 for instance.

I have always thought that no additives are necessary on post-war mercedes engines and that these have been designed considering that lead will be forbidden in the future. Aluminum heads with strong valve guides and seats.
What do you think ?

oscar

I've wondered the same thing in the past, especially after reading my manual that stated in 1973 the recommended fuel was premium.  Although that premium, I assume, would've had lead in it, in Australia only 91 ron or lower was available. No 95 ron or 98 ron premium.

It got me thinking, since my car M116 motor has used the following; low ron rated leaded fuel for approx 250,000km; another 130,000km on low ron unleaded and a couple thousand since I've had the car on a range of lead replacement petrol, regular unleaded and 98 ron premium with lead substitute,  how's the engine holding up after nearly 400,000km.  After a recent service addressing timing chain, valve seals and valve gaps the engine runs great.  So I don't know what if any damage has been done.

I've also heard that the V8's had hardened valves.  Regardless, thanks to advice from Styria, it made sense to me to add upper cylinder lube additive to a 98 ron fuel.  I can't find Styria's post but hopefully he or someone else may throw a bit more science or proof as to what we should use with what's available today.
1973 350SE, my first & fave

Tomi

Thanks for your answer. Someone here has also said (from some MB history book)  that the V8 engine specially was designed to scope with unleaded.

But I am very puzzled on this.

The forums in US state as follows and they all seem to agree:
"All MB engines with aluminum heads (which is everthing since the 50s except the diesels) have hardened valve seats and are fine with unleaded gas. Only cheapo cars with the valve seat ground directly into the head casting had problems with unleaded fuel (read Ford and Chevy "old" six cylinders). "

and from Germany:
"No Mercedes car ever needs leaded fuel. There is an official service information about this matter which actually forbids any fuel additives."

I think I will have to ask directly from the classic MB centre in Stuttgart about this.

Regards

Mforcer

#3
Thanks Tomi. Do you have a source for the two quotes but especially of that from Germany? This also raises the question of whether engines and in particular valve seats differed between countries, not that I would expect any differences.

For the record, my 1977 M117 has been running on 98 ron unleaded without additives for the past few years and not shown any problems. Admittedly I am doing less than 6,000km each year.
Michael
1977 450SE [Brilliant Red]
2006 B200

AMG69

I've got a UK Test of the 6.9 from 1978 and they had 98 octane fuel way back then. We Aussie were a "little" late in following suit!
sigh....sitting back contemplating the next purchase..!

oscar

See this pdf of what BP recommended when LRP was phased out. Found at mb club nsw forum by another member click here.

I see they forgot to mention a 350, again!!! >:(   But why are >1978 280's and >1976 450's ok?  What happened in those years?  It cant be type of fuel systems employed can it?

For god's sake, someone ring Stuttgart and find out please.  Either that, or make something up and sound convincing!  Cheers.
1973 350SE, my first & fave

John Hubertz

In addition to the hardened valves and seats, I have read that all MBs since before world war II also have sodium-filled valve stems, MB invented the technology.  Sodium provides the cooling necessary for higher unleaded fuel combustion temps and also explains why you rarely find a dropped valve on our USA cars that are so often run on 85 or 87 octane unleaded fuel.

John
John Hubertz
"When the going gets weird, the weird turn pro."
(Hunter S. Thompson) 

1977 450SEL (Max Headroom)
[img width=68 height=73][url="http://i48.photobucket.com/albums/f248/fullhappyfish/max.jpg"]http://i48.photobucket.com/albums/f248/fullhappyfish/max.jpg[/url][/img]

Tomi

Hello,

I have now received a clarifying answer from Stuttgart Mercedes classic centre as follows:

The question I sent was:

Dear sir,

Can you help me with the following question

I wish to know if unleaded fuel is OK with the following old mercedes cars:
450SEL (M117.986) year -80 and
280E(110.988) year-82 and
230E (M102)year-82

Is a lead substitute additive to the fuel necessary to use with these cars?
thank you for your answer

Regards, Tomi Toratti

And the reply was:

Dear Sir,

Your question about the use of unleaded fuel is easy to answere:
All Mercedes-Benz cars (pre-war and post-war) have absolutely no problems
with unleaded fuel.

We recommend to use fuel with an octane rating of 98 (ROZ) for every type
and also a regular
control of the valve clearance, twice as much as specified by the factory.
In our experience no additional lead substitute additive is necessary.

A normal use of the car is required, of course.

We hope this will help , please feel free to ask if you have further
questions.



Mit freundlichen Gr??en /Kind regards

Andreas Hosch
DaimlerChrysler AG
Mercedes Car Group
Brand Communications
Mercedes-Benz Classic Center
000/R051 - MK/CL
70546 Stuttgart
Phone: +49 (0)711 / 17 -8 40 40
Fax:      +49 (0)711 / 17 -8 34 56


This must be clear now


OzBenzHead

Hey, Tomi!    ;D

Many thanks for sharing that valuable information with us. It's a question I see/hear frequently, but there have been no such definitive answers before.

I have taken the liberty to post the response on other forums (OzVets http://forum.mbspares.com.au/ and W116 Mercedes Benz Group http://w116mercedesben.bbfunplus.com/w116mercedesben.html?).
[img width=340 height=138][url="http://i12.photobucket.com/albums/a215/OzBenzHead/10%20M-B%20Miscellany/OBH_LOGO-2a-1.png"]http://i12.photobucket.com/albums/a215/OzBenzHead/10%20M-B%20Miscellany/OBH_LOGO-2a-1.png[/url][/img]

Tomi

#9
by all means OZbenz, I think this info is good to spread and good to know of the other forums too.

Tomi

#10
hei Styria,
yes I have been wandering about this for some hours now and myself, I have come to the following result: I will not use any lead substitutes anymore on any of my benzes. The recommendation for checking of valve clearance more often I think signifies that some wear must occur on the valve seats, but since milage on these cars is normal ( I mean not taxi use) it is not relevant . I remember you Styria saying that hydr. lifter static clearance has to be cheked at some intervals, maybe it is due to this. regards from minus 10 C (3 days before minus 28C)

Mforcer

Quote
Your question about the use of unleaded fuel is easy to answere:
All Mercedes-Benz cars (pre-war and post-war) have absolutely no problems with unleaded fuel.

Quoted for importance.

QuoteWe recommend to use fuel with an octane rating of 98 (ROZ) for every type and also a regular control of the valve clearance, twice as much as specified by the factory. In our experience no additional lead substitute additive is necessary.

A normal use of the car is required, of course.

Could it be that they mean to check the valve clearance twice as often as specified even for normal use of a car?
Michael
1977 450SE [Brilliant Red]
2006 B200

oscar

Thanks Tomi, much appreciated.

I also was confused about the valve comment and 450SE's comment makes sense as well.  I don't understand why there'd be a need to pay more attention to the valves, by way of frequency of maintenace or gap settings? 

I mean, if no additives are needed and the valves are safe and supposedly the car's been running on high octane fuel since new as recommended by manufacturer. ,,,, I dunno.



1973 350SE, my first & fave

John Hubertz

The reason the Mercedes source would advise additional attention to valve clearance is the loss of the lubricating and heat-dissipation advantages of leaded fuel.

Due to the significant additional heating of the valve and potential for increased seat and valve guide wear, they are recommending cutting the recommended service interval in half for cars with mechanical lifters and adjustable valve clearance.

The most telling example of this I am aware of is the need for near-constant valve adjustments on vintage volkswagens with mechanical lifters when operated on modern unleaded fuel.  I think it is mainly the increased heat - and valves go wildly out of adjustment rather quickly.

John Hubertz
"When the going gets weird, the weird turn pro."
(Hunter S. Thompson) 

1977 450SEL (Max Headroom)
[img width=68 height=73][url="http://i48.photobucket.com/albums/f248/fullhappyfish/max.jpg"]http://i48.photobucket.com/albums/f248/fullhappyfish/max.jpg[/url][/img]

OzBenzHead

Quote from: John Hubertz on 09 February 2006, 09:07 PM...  they are recommending cutting the recommended service interval in half for cars with mechanical lifters and adjustable valve clearance.

Okay - I'm out of my depth here. I understand the theory, but have no idea if my cars have mechanical or hydraulic lifters, and haven't been able to readily find the answers.

If anyone can enlighten me (see list below for my cars), I should be most grateful.
[img width=340 height=138][url="http://i12.photobucket.com/albums/a215/OzBenzHead/10%20M-B%20Miscellany/OBH_LOGO-2a-1.png"]http://i12.photobucket.com/albums/a215/OzBenzHead/10%20M-B%20Miscellany/OBH_LOGO-2a-1.png[/url][/img]