Does some one have experience in converting a Mercedes old timer, to LPG “liquid petroleum gas”? Probably not a popular question whit the pure Mercedes collectors, but gasoline where cost’s 1.04€ liter, that’s 4.43$ the gallon I believe. Tnks

Most LPG conversions to cars with carburetters or mechanical or electro mechanical injiction involve passing gaseous LPG into the induction path at an early stage. This can work well, but the engine must be in excellent condition and the ignition must be exactly right. If combustion or ignition is poor, then a backfire will literally blow your induction apart. I have seen pitures of exploded air cleaner housings, and worse.

Modern engines with electronic engine management can cope with liquid lpg injection near to the inlet ports and can have the ECU linked to the gas ECU. This avoids most of the problems.

Also bear in mind that LPG has no lead in it. You must have an engine that is capable of running on unleaded fuel, otherwise your valve seats will burn out quickly.

My employer is an accredited LPG converter. We get excellent result on modern engines, but have seen too many distasters on older cars to even consider it. If you want to save money on an old MB, buy a diesel.

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Cheers, Neil

Tnks for the answer, in fact I’m looking for a diesel, 220D or a 240D (w115). We have many where because they were very popular with taxis but unfortunately all I have seen are in very poor condition. I came across a very nice 450 SEL, 1976, in good condition and not so expensive so I was wondering if it would be a good Idea to convert it to LPG. Do you know if a 190E (from the 80´s) whit 150000Km is a good candidate for LPG.

I don't think the 450 is certified for unleaded so you would have to replace the valve seats.

Later 190s (like my 1987) will run on unleaded so no valve seat problem. Not sure about the very early production, though. The 190 has K-Jetronic injection which, despite the name, is electro-mechanically controlled. You might get a satisfactory conversion but at 150k, the engine is going to need a lot of work to get it running perfectly.

Some people do get early MBs to run on LPG, but I would stay clear if I was you.

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Cheers, Neil

I would accually say it does have harden seats valves. Hell, the M129 engine in my 1966 250SE does!

Let me see if I got this correct, the 450 as harden seats valves so it’s a not a good idea to do the conversion. The 190 have electro-mechanically controlled injection, you can convert but the results aren’t perfect. Ill put the question on the lead and the injection of the 450 just out of curiosity.
My father as a 190E and is running on unleaded for same 75000km whit no problems so I would guess Is not a problem.

harden seats valves = good
normal seats valves = bad

You car has the 6.9L V8 doesn't it?

It’s a 4.5L and I’m still considering buying because of economy. I’m looking for a w115 , 220 or 240 and came across this one, not too expensive and in good condiction.

Ok, if the 450 has hardened valve seats and it will run on unleaded, then LPG won't burn out the valve seats. Most aluminium cylinder heads will run unleaded even if the manufacturers say otherwise.

I know later 190s will run on unleaded, because I had one. I believe there were some doubts about the early, 84 or 85, engines.

Any older engine must be in good condition, especially as regards the ignition, to run safely on LPG. A worn distributor that leads to inaccurate ignition timing can lead to detonation, over heating and backfiring. A backfire in an LPG engine is very serious, and can destroy some or all of the induction system. A petrol engine can still run OK with poor condition wires, plugs, coil etc, but these are all a problem with LPG.

So it sounds as if it will be possible to run the 450 on LPG, but you run the risks I set out above.

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Cheers, Neil

Tnks, this is valuable information, Ill make sure not to allow my self to be tempted unless the car is whit a perfect engine.

I got the engine n.º and same more details.

117.986.12.XXXXXX
450SEL Sedan 116.032.12 1976 - 0 Mech K-Jet FI (8.8:1 Compression Ratio)