As the original subject of this thread was concerning engine oil, I thought I'd jump in with this.
As has been mentioned by folk above above, I'm not at all keen on extended interval oil changes. I do the family vehicles every 12 months or 10,000 miles - at a pinch I'd let the mileage go out to 12,000 if it's on a car which doesn't do much stop start/city running but i wouldn't exceed the 12 months on a lower mileage car. For me this means the cars get serviced just before their MOT is due which also gives them the best chance of passing. The only exception I'd make is brake work as I'd want the new friction material to have enough running time to bed in properly.
Considering the actual oil itself. I think you need to consider what the engine in your car is. By this I mean is it a fairly simple, possibly older, design, like our F.I.R.E. engines or my daughter in law's old Honda Jazz or, indeed, the 2014 Mazda 2 she's just bought to replace it. Engines like these, with low pressure port injection fuel systems and no turbo don't place particularly great stresses on their oils and I think a reasonable generic make of oil which meets the viscosity and other manufacturer's specs will be absolutely fine - so no need to buy a really big name expensive oil. Changing it regularly is far more important. I'd happily use a brand like Comma, TradeTEC (now NAPA), Granville, and many others you'll find on offer. The only thing that would temp me to use a more expensive oil in an engine like this is if it has a timing chain. Good quality, clean engine oil which is changed regularly really is important if timing chains are not to give trouble.
Then there's anything with a Turbo, Common Rail fuel injection, Direct injection, etc, etc - so pretty much all the current generation of small capacity engines you'll find in today's vehicles. Turbos in particular place great strain on engine oils due to heat which tends to break the oil down. The high pressure fuel pumps, mostly plunger operated from a lobe on the camshaft, need a high quality lube too then there are variable output/pressure oil pumps, and a plethora of stuff like restrictor valves, piston cooling oil sprays, actuators for the likes of VVT pulleys and more, much more. This is before you consider the evidence now emerging of the increasing understanding of the roll played by the lubricant in carbon fouling of inlet tracts and Low Speed Pre Ignition. These small, high power output, modern engines have very specific requirements and their oils are very nearly engine specific now. You need to either use the specific oil recommended by the manufacturer, and I don't just mean that if you see a Castrol sticker under the bonnet you think you can chuck in any old oil as long as it's in a Castrol tin! Or, if you want to be more budget conscious, you need to check out actual oil specs. This can be a real minefield if you don't have a fair bit of knowledge so consulting someone like Opie oils or Powerenhancer, to name just two, will keep you on the right track.
In my case, I've always been very fussy about the family diesels because of their turbos but also because one had the VAG PD engine which requires very specific oil if damage is to be avoided to the rather narrow cam lobes/followers. Both the above mentioned suppliers were very informative - The Powerenhancer people can get very technical if you want to go there - I can recommend a visit to their websites.
Having established exactly what oil you are going to go with I always try an online search for special offers. Opie oils often have good spot offers which don't seem to come up on their website. A wee word of caution about on line offers though. Check with the supplier on manufacturing date for the oil they are going to send you. It seems that an unopened oil can be sold as "new" up to 5 years from it's production date (most have the production date on the container) I've never had one older than 6 months from either of my above preferred suppliers and usually less than that.
So what is my current preference? Well, for many years now I've been running "the family fleet" on FUCHS oils and everything seems absolutely fine, no oil related problems and I have great confidence in this manufacturer. My boy's Astra we've just sold on with approaching 130,000 miles on it and it doesn't use a drop between services! In the Fiats (our 2010 Panda FIRE 1.2 60hp and my boy's 2012 Punto 1.4 8 valve) I've used this:
https://www.carservicepacks.co.uk/product/fuchs-titan-gt1-5w-40-xtl-5ltrs/ Last service I changed to this:
https://www.opieoils.co.uk/p-60166-fuchs-titan-gt1-flex-3-5w-40-synthetic-engine-oil.aspx which is now the latest version of the oil and slowly replacing stocks of the older "brew"
The Ibiza I'm running on this:
https://www.opieoils.co.uk/p-980-fu...lly-synthetic-engine-oil.aspx?variantid=91534 which I changed to as soon as she was out of warranty following the dealers, inexplicable, inability to tell me what oil they had been filling her with during her warranty period services!!!??? She's running very sweetly on it. Of course I don't pay the price you see in this advert as I always look for offers, like this for instance:
https://www.ebay.co.uk/itm/16505326...hWLsvGl+A/raY5Shi6/kdN/L0A==|tkp:BFBM_qyO_-9h By the way, Fuchs have only very recently been using these wine box type "oil cubes" so you can be sure oil packaged like this is new stock.