Jim's giving you a lot of good and very sound info here. It's very easy to become a bit obsessed and worried about oils and filters etc. I think partly because there is a lot of advertising around them and a lot of horror stories from people who have had bad experiences. - not always directly the fault of the oil/filter, but the people thought they were.
Like Jim, I would advise investing in a good oil from a known good manufacturer but most of all, if you want peace of mind, choose an oil which complies with the Fiat specification for your car. Then, regardless of the oil's manufacturer, you will be using an oil formulated to Fiat's recommendation for your vehicle. (for instance our Panda and Punto take an oil to Fiat spec 95535-S2 (if my memory is correct)
Both cars spend the largest part of their mileages running around the city of Edinburgh. The Punto does around 8 to 9,000 miles per year and the Panda does 2 to 3,000 miles. Both cars get their oil changed once a year. I run them on Fuchs Titan GT1 5W-40 which is an ACEA 3 oil which meets the Fiats spec, but I'd be equally happy to run on Castrol, Mobil, Liqui moly, or any other oil which meets the spec. Personally I like Mahle filters or a genuine manufacturers branded product but I recognize most of the names you quote and I think you're going to be pretty safe with any of them, although I don't know the Muller or Kengst brands. Same goes for air filters.
Personally I don't like engine flushes, especially on older engines - which, ironically, they are most recommended for! It worries me that "mucky particles", which otherwise would remain safely tucked away in corners of the engine, will become detached and block up, or partially block up, things like sump pickup strainers and restrictor orifaces etc. Regular oil changes, even with an engine which is quite dirty inside, is likely to very slowly dissolve some of the deposits using the oil's own, less aggressive, detergents so avoilding blockages and the bits it doesn't dissolve? who cares, they can just stay safely tucked up in the wee nooks and crannies of the engine.
Oil additives which are intended, nearly always, to "improve" the performance of the oil or somehow (which is never well explained) give "magical" extra protection? Honestly I just wouldn't. Spend your money on a really good oil instead and change it regularly ( yearly or around 10,000 miles will be fine for most cars. Although Jim likes to change his more often because he's doing low mileage short journeys which will degrade the oil more quickly. I think he'd probably be Ok doing it once a year but I bet his car loves him for doing it every 6 months) A modern oil is a very sophisticated "brew" of many constituents. Start adding random quantities of unmatched additives and you may just completely upset the carefully balance "apple cart" and end up with a lubricant which has many of it's best properties compromised!
So, I hope some of that is helpful? By the way I buy my oil in 5 litre containers. I don't quite get both cars changed with one 5 litre container so I have to buy 2. Reputable manufacturers will date stamp the containers and, as far as I can find out, It's acceptable to use oil up to 5 years from manufacture. So the next year I buy just one container and use some from the new, last year, container and some from the new, this year, container in both cars.
There are some great bargains to be had on ebay but be careful because sometimes you'll find it's product just about to go over the recommended date. No-one mentions this. I watch for Opie oils special offers on ebay which often undercut their web prices. Powerenhancer is another worth watching. Sometimes my local factor has a special offer. I've never had "old" oil from any of them.
Kind regards
Jock
