Without knowing the actual oil spec used I can't make any comment other than to say Castrol is one of the biggest and oldest names in the "oil game" so, as long as it's the correct spec - So something like a 5W-40 to API SN or ACEA C3 (but others are also suitable, you need to check the vehicle manufacturer manual) Opie oils also has an excellent oil finder which works with your registration number and gives a choice of different brands which are suitable.
The NAPA brake fluid will be fine, used it myself.
Likewise for the coolant - I've got some in our "Becky" right now.
The recommended Petronas Tutela Technyx gear oil is an API GL 4plus oil of 75W-85 viscosity fully synthetic of course as most are these days. The "4 plus" rating is a bit unusual and, I believe not actually listed in the API specs. However I've done a lot of searching and am pretty sure its basically a GL4 with some of the advantages of a GL5 in terms of lubricity but without the additive problems which the GL5 can cause to yellow metal components. From what I can see the 75W Napa oil is a "straight" GL4. If so it won't have the potential problem a GL5 might have. My guess would be it's probably going to be fine but it isn't, from what I can see, recommended by Fiat.
The GL4/GL5 "thing" is a bit complicated. When GL5 first came out it was formulated differently to GL4 - which had been on the go for years. It contained more extreme pressure additives (and other stuff too) so was considered superior to the older GL spec. It didn't take long for stories of transmission failure to start rolling in! The technical reason is quite complicated but you can think of it as a leaching problem with yellow metals - so stuff like synchro rings, gear selector forks, bushes and plain bearings. Anything made from metals like brass and bronze. The problem was that, on paper the GL5 product looked superior so many folks were sold it as a superior product by sales people who has no technical background or they, the customer, would see the adverts extoling it's virtues and buy it in ignorance. Lots of expensive damage was done to boxes with yellow metal content and, although "the word" started filtering down it was never really taken on by everyone and you'd sometimes hear of another one that had been damaged. So, as far as I'm aware, the big name oil producers started modifying their formulas so their GL5 rated products wouldn't damage a box for which GL4 was specified. I've no idea if every bottle of gear oil with a GL5 label on it will be compliant or if it's just the major brands or whatever. I also wonder if new old stock is still filtering through the system. So I stick religiously to the manufacturer spec for any vehicle I'm putting transmission oil in. If it says 75W-85 GL4plus then that's what it will get, If it says 85w-90 GL4 then I'd move heaven and earth to find some, and if it was something with a GL5 spec, I'd be looking for a GL5.
Group Auto/Alliance, under whose flag NAPA now does business in Europe, and seems to be popping up all over, sold branded engine oils - Trade Tech and Truck Tech - which, I was told and have seen on the internet, were/are made by Exol. I've used them and had no problems. However I believe engine oils branded NAPA in the States are actually made for them by Valvoline? So I really don't know who's product is in the NAPA UK containers but might guess it's EXOL?
www.castrol.com
www.shop4parts.co.uk
