If I'm planning 6-month, 5500-6000 mile OCIs, what's a good oil for all year round that won't break my piggy bank? The car is an '03 Buick Park Avenue, non-supercharged, with the famous 3.8L V-6. It uses about a quart in 5000 miles, though with the thinner Castrol Edge that's in there now I'm seeing a little more oil consumption. Car is driven about 80% city, 12-mile highway runs to the suburbs about 5-6 times a month, and the hot weather here gets the oil up to temp pretty fast, I'd judge. Our winter, unfortunately, is blink-and-you-ll miss-it, rarely getting below freezing. So my plan was to buy a year's worth of change, 2 5-quart jugs and two filters, before prices go up. I was going for Motorcraft's semi-synth 5W-30, which was supposed to be on sale for $12 per 5-qt. jug at Walmart, but the two stores closest to me have only 5W-20. Yes, the Valvoline MaxLife semi-synth would be good, and might reduce my oil consumption; but will it affect my gas mileage? Or would a good dino like Pennzoil handle 6000-mile OCIs?