oil and brake fluid for 1994 Pontiac Trans Sport

Where you are, in the Canary Islands, you sure don't need the 5W rating, as you do not get below freezing temps, and 40 or 50 weight is great for high temps. I would use 15W40 or 20W50 without thinking twice. (I've had "tropical" experience in central Africa) As for the brake fluid, definitely use DOT4. It has a higher boiling point and a few other "improvements" over DOT3. Do a complete flush and replacement to get the maximum advantage.

Some "experts" will warn against wide spread oils like 10W40, stating there are too many "long chain Polymers" in the viscosity improvers, that break down causing viscosity breakdown. In my experience that is only a problem with today's oils if you extend the drain interval too far. Change oil 4 times a year, maximum 8000 miles, preferred 5000, and the "problem" will never occur, assuming you are using premium quality motor oils. (Agip, Shell, Mobil, etc)