In what year did MB start manufacturing vehicles to use unleaded fuel?? Would it be possible to change the cylinder head, distributor and valve seat inserts in a leaded engine and use unleaded fuel in it? Or premium unleaded if the octane wouldn't be high enough...
If this is a stupid idea just tell me, I'm not sure I had even been born when unleaded fuel was introduced.

I was just doing some reasearch and it seems that a lot of MBs, pre-1986 can use unleaded fuel for at least 4/5 fills or 100% of the time. I've been using LRP in my car for six months, and no one told me.

That's another $10 a week I can spend on soda. Or $240 I could have spent on my car.

MB redesigned valve seat material in 1975/76 depending on the model! Pre 1975 (gas) cars need frequent valve adjustment to keep from burning the valves.

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MB has used hardened steel inserts in the aluminum heads for a very long time. Other than possibly more often than normal valve adjustments, they should be fine. My owners manual for the 72 280 SE 4.5 says it is fine to use unleaded.

I've never been able to figure out how lead oxide (a mild abrasive) prevented valve seat wear anyway -- I'd have thought that lack of metal oxides ( MMO aside, since it isn't used any more) would make the valve seats last LONGER, not wear them out faster... Hmmm

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Grrrr, I'm even more pissed off at the dealer now. Never trust a "perfomance" car delearship that just wants you to buy a skyline and get out.

Psfred, how is it that your '72 owners manual says that you can use unleaded, and all my owners manual says is 98RON/88MON premium fuel?

Last time I saw unleaded was in about 1986, when I got rid of the Audi Fox (blast to drive, what a rustbucket!). I've not looked since, but leaded regular vanished shortly after that.

Premium rating (and octane) have nothing to do with lead content, except that tetraethyl lead is a wonder octane booster, used in moderation -- that is, if you ignore the serious toxicity problems! Premium went unleaded in the late 70s, I think, certainly I found that Amoco had unleaded premium (92 octane) in 1980 while I was still driving the Toyota Crown, which used 95 min. I traded it for the Fox when Mobil closed their last station in Evansville, since they were the last one (except Sunoco, and I didn't like their fuel) to sell 95 octane leaded premium.

Unleaded fuel has been around so long now I don't remember when it started, certainly in the early 70's.

The excessive valve wear thing was, I think, blown all out of proportion by Ford and GM, both of whom were still selling engines with valve seats ground directly into the cast iron head, with no insert. They also blew enourmous smoke about emissions controls, only changed their minds when California outlawed internal combustion engines the first time (1965).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I think this has come up before, but lead and valve seat wear is a smoke screen propagated by Dupont so that they could patten their leaded formula for high test gasoline.Lead added to regular gas made a higher octane, the Romans knew that. Hardened valve seats were simply to make engines last longer......I have to guess that lead helped make sludge in older engines....
William Rogers.......

I started a thread posing this question some time back.

I have a 1983 Euro 280SE which MB recommended an unleaded conversion when I posed this question to them. I had been placing lead substitutes regularly, but was planning a head job due to leaking valve seals with heavy oil consumption and plug soilage.

After cleaning the parts, the valve seats were still in a pristine condition with no sign of wear (after 20years/180,000km). Talking to the machine shop, who have handled a few w123s conversion, all that needed to be done was to replace the valve seats. However, they have not seen any valve seat problems all this while with cars who have run unleaded against MB recommendation.

A poll of independant MB workshops in my area have unanimously concluded that valve seat recession is a myth and unleaded is safe to use. I would agree with that: I have not been able to obtain hard evidence, and have found a lot of "hearsay" putforth.

However, I still put in lead substitutes occasionally out of force of habit and as a hedge just in case......

kennysin

Kenny:

Lead substitutes are for octane enhancement, not to replace the putative lubricity of the lead.

I've though for years (since my high school chemistry class in 1972, in fact) that the lead in fuel acting as a valve lubricant was pure bull-- no way it's going to stay METAL in a high temp oxidizing atmosphere, and metal oxides aren't exactly what I would call a lubricant (India stones are aluminum oxide, for instance.....).

Lower than necessary octane, on the other hand, will burn valves and pistons pretty fast! However, I'd believer current octane standards over what they were in the 70s -- things were pretty fast and loose in those days.

So long as the fuel you use is rated at what the engine requries, you are fine. Adding octane boosters above what is required can make for ignition problems -- it is entirely possible to make the fuel nearly impossible to ignite!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks.

This has been a bit of a pet subject due to the number of old cars which have passed through my hands (manufacturer stand):

1979 Daihatsu Charade (unleaded ready)
1987 Saab 900 (Not unleaded ready)
1983 w123 200 (Not unleaded ready)
1983 w126 280se (Not unleaded ready)

It was interesting to note that Japan was ahead of the game in the late 70's with their cars unleaded-capable!

I fill mine with premium 97 RON.......I agree lead substitute is an overkill.

kennysin

Lead (Pb) is a pure element, it is ALLWAYS a (transition)metal, cannot be anything else.

Just for clarity

Burned tetraethyl lead is lead oxide. I suppose some metallic lead might exist in there, but that whitish gray stuff on the valves and spark plugs sure ain't metallic lead, it's lead oxide or lead nitrate.

Being a transition metal has nothing to do with oxidation state, it has to do with the electron orbits filled to balance the the number of protons in the nucleus rather than the number of electrons any particular atom has at any given time.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I have been running my car on Premium Unleaded (98 RON) since the day I got it (7 months ago). I have never had a problem. This is my 1966 250SE, with an M129 engine.

Even the VW beetles since 1965 have hardern seat vavles and can take unleaded.

I know an older chemical engineer who worked on the lead issue for a number of years.

One of the official rationales for claiming that tetraethyl lead would protect valve seats was that the lead oxide layer left behind after combustion would form a perpetually renewed ablative coating.

This was accepted as an article of faith for decades, until when the great unleaded controversy started, SAE actually lab-tested identical engines, and learned that TEL in the fuel actually caused increased engine wear -- not just around the valves, but of all internal moving parts. Some of us remember when even meticulously maintained engines were uselessly played out by 100K miles.

I miss having really high octane for cheap, but the horrendously bad health effects of lead, plus increased engine wear, and its incompatibility with catalytic converters, made getting rid of it a Hobson's choice. It had to go.

What I find interesting is the speed with which the rest of the world is now ditching lead as well. Much of this is reportedly being driven not by health and environmental concerns, but due to automakers' cost structure. The manufacturers want to run production that is as globally uniform as possible. A case of their doing a collectively good thing for directly selfish reasons, which does happen now and again.

Now if we could only get rid of the ethanol and/or MTBE that the feds are perpetually forcing upon us and into our perfectly good gasoline. Sheesh. You would think the lead lesson would have been learned.

His statement, that I quoted, spoke of lead, not lead oxide.

Just nit picken.