You are right to be concerned about running an older vehicle on modern motor fuels (gasoline or diesel) and its long term adverse effects on engine internals as well as longevity of fuel tanks, fuel pumps, rubber seals and hoses.
Phasing-out of leaded gasoline motor fuels began to occur in the mid-1970s so, in the case of an early 1990s Puch 230GE, one could reasonably expect that M-B’s engine design already accounted for lead-free gasoline.
It’s the more recent watering-down of gasoline motor fuels with ethanol (E-10/E-15/E-85) that is a bigger problem older gasoline engines. Ethanol is a low-cost plant-based “filler” in gasoline but it is not inert. Ethanol is both hydroscopic and a powerful cleaning agent so expect problems with crud & water in your fuel system (numerous fuel filter changes). For carbureted gasoline motors, ethanol plays havoc with float levels and air/fuel ratio calibration, causing them to run lean and hotter than normal. I found this out when I had my carbureted Pinzgauer 712M. Fortunately, the M102 engine in the Puch 230GE has Bosch KE-Jetronic fuel injection. Ethanol won’t allow nitrile rubber seals to swell properly and will slowly deteriorate those older nitrile rubber seals and hoses. Ethanol also attacks some metal alloys, particularly certain aluminum alloys often found as anti-rust coatings in older steel fuel tanks. Owners of older gasoline-powered vehicles have two choices; either gradually change out components not compatible with ethanol with modern replacements or always be on the hunt for ethanol-free gasoline. Me, I won’t even use any level of ethanol-laced gasoline in my “modern” 2011 G550; I’m always on the hunt for real gasoline. There are websites like
www.pure-gas.org to help with the quest for ethanol-free gasoline.
ULSD motor fuel use in older diesel engines has its own laundry list of problems. Pure dino juice diesel fuel naturally contains sulphur. The sulfur in these older diesel fuels combines with nickel in the engine's metallurgy to create a molten alloy that enhances lubricity, a property that engineers anticipated when designing these older diesel engines for sulphur-laden fuels. Newer diesel engines are designed for ULSD fuel and don’t require the added lubricity which sulphur once provided. Removing sulphur from diesel fuel also drastically drops the fuel’s cetane rating by 5 to 10 points. In areas with colder climates, diesel fuel suppliers also create winter diesel fuel by adding ant-gelling agents. This too lowers cetane rating and it’s quite noticeable in a low-horsepower engine like the OM602 found in the 250GD Wolf. So for my Wolf, I use diesel fuel additives to both restore fuel lubricity and increase the cetane rating (I use Opti-Lube diesel fuel additives).
Arie