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Thought I had replied.
Didn't know about the ring gumming problem, thought if there would be issues were with the pumps. The VW engines were supposed to be fine on I used SVO as I was lazy and could get 20l for £15 so ran the 2.2 laguna (called chippy as it smelt like a chipshop) on that but used to go through halfords glowplugs in about 6 months a set. But then they were being replaced for free.
Bore gauge, that is posh isn't and old piston ring and feeler gauge enough for you ;) Had access to a scanner that I found fascinating as the accuracy was interesting as you could 'see' different manufactures tolerances. Lancia v4 tolerances were better than the ford/lotus pre crossflow blocks compered to the ford pre crossflow and crossflow block from around the late 60s, then manufacturing gets better at ford for the crossflow blocks used in formula ford.
lynx-
Rest of system happy running on whatever. Pump is super happy with its life!
Never thought of using an old piston, don't have any floating about either. Was i think £120+ vat (become a work tool now) which is obviously at the cheap end of a tool like that but im only ever gonna use it a few times.
Worked briefly in a metallurgy lab, they had some epic tools, made use of their mad money cmm a few times for checking stuff, the whole room it lived in was specially made from the founds up to have this specific machine put in it. What amazed me was how easy and quick you could get data out of it, the future!
BrickMan
Yup using veg from a friend who was brewing it from waste oils from a large base near here, also using a mix from a retail operator in the other end of the city (has duty built in so was barely aby cheaper thwn regular diesel). And yeah gumming issues started happening within a few thousand miles of first use.
Pump etc is dead happy just the rings! Oil gets changed regularly (quantum synta 10w40 which is vw trades own brand oil for vp and pd engines, its like £9 for 5 litres) every 6k.
Having worked on a few they rarely go mechanically bad, it's more their ageing control systems and mechanics that aren't familiar with them that is the common cause for them to end up in the bin.
Was at least 2 years of not 3 since last using anything other than pump diesel, but still the damage has been done. Tried leaving cylinders to soak in that carbon melting stuff (some kind of stinking organic compound) just before an oil change but made no real difference.
Has all new rings in it now, gaps and wear seem ok, had to buy a bore gauge as my friendly engine builder is shut, often borrow his sexy spec tools.
Lesson learned cheap fuels or improper use kills engines