Is there any improvement by using synthetic engine oil on a 500 engine?

Thanks

you can go longer periods/miles before changing the oil

maybe worth it on a new 500 but not on an old one(classic)

i was told that older engines are better off with non-synthetic oils, apparently allows the muck to be suspended in the oil better? not sure if it's true?

For what it's worth, my mechanic in Italy told me not to use synthetic oil.

If the engine is clean inside or rebuild, there's no reason why you shouldn't use a good quality synthetic oil.
If the engine is old and dirt has build up inside, you have to be carefull though, the cleaning habits from synthetic oil may dissolve dirt that may block oil lines.
The benefits from synthetic oil are, among others, that it will act like a preservation oil during long stand still periods.
I personally don't lengthen my oil intervals, I keep the normal drain intervals, even with synthetic oil.

I really wouldn't go for the extra expense. Synthetic oil holds its grade longer than semi-synth and is better in high performance and tuned engines but in an old engine designed for semi-synth or even monograde I wouldn't go there. As per previous poster its cleaning / searching effect can be bad news on old engines with worn bearings where it cleans out the crud taking up slack in bearings and you might find small oil leaks around pipe joints. Not always but possible.

Just put in a good brand semi-synth oil and change it at 2/3 the recommended mileage.

If you really insist on changing from a mineral oil to a synthetic or semi-synthetic oil, use a flushing oil first. These oils are usually rated 0W20, or something like that, and are not for normal use - they are used to clean the crap out of engines - though I think some hybrids use a 0W40 oil. A 0W20 oil looks like light brown coloured water and will not get viscous enough to protect your engine, so please don't drive around with a sump full of it as you'll ruin your old engine.

What you should do is drain your old oil, leaving your filter in place. Fill the sump with flushing oil and run the engine with no load for about 20 to 30 minutes until it gets warm but not hot. Drain the flushing oil, change the filter and refill with your choice of synthetic oil. Job done.

However, I must admit that I can't really see the point. These engines were built during the times of mineral oils, so I'd reckon unless you absolutely have to, leave well enough alone.

Happy Easter,
Chris