i think ive asked this here before, just wanted to be sure. neighbor of mine has a 2005 ford taurus, 3.0 Vulcan V6, 50,000 miles. she wants me to change her oil tomorrow. its spec'd for 5W20, but was thinking of going with either Supertech 5W30, or Pennzoil 5W30, and a Motorcraft FL400S filter. can it hurt to use 5W30? didnt they spec 5W30 when the vulcan V6 was in the ford rangers? also, she does alot of extreme short trip driving, 4 mile round trip to work and back, besides that, not much driving. so instead of going by mileage, would it be safe to go with an oil change every 3 months instead?