I'm using Mobil 1 synthetic in both of my S10 Blazers and my Impala SS with good results. By good results I mean no leaks, good gas mileage, and it keeps the inside of the engine very clean. I also ran Mobil 1 in my Crew Cab before I totalled it. Your climate, driving style, and driving conditions really are important when choosing oil. Right now I'm running Mobil 1 European 0W/40 in my 96 Impala and my 88 S10 Blazer because it offers great low temperature and high temperature protection plus it has the highest amount of zinc of all their oils for reduced wear. I run their 10W/30 High Mileage in my 05 ZR2 since it has 150k and a slight oil pan leak. I also use K&N oil filters on all 3 vehicles since they have one of the highest flow rates and lowest micron filtering of all the oil filters out there. They also have a 1" end nut on the end which simplifies removal and installation in tight areas. I use K&N part # 2001 an all 3 vehicles. This is the tall filter. Part # 1001 is the short filter, but I don't see any reason to use the short filter unless you have a vehicle with limited access which is not the case on any S-series I've seen. Royal Purple and Mobil 1 also make good oil filters. Stay way from anything cheap like FRAM! For normal driving you can go 10k miles with synthetic so it's easily worth the extra money. If this is your first oil change make sure you don't over tighten the oil pan drain plug which has aluminum threads. 20 ft pounds is the most I would go. You will need 4.5 quarts if you use the short filter or 4.75 to 5 quarts if you use the tall filter. Wal Mart is by far the cheapest place to buy oil and it is also much cheaper to buy the 5 quart jugs than individual quarts.
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*