The wife's Envoy is a leased vehicle and according to the manual, I only need to change the oil when the OLM light turns on or after one year. Well, after 10 months and 10,000 miles the light still had not turned on. Since we will be driving to Houston in a few days (1,600 miles) while towing a small trailer, I thought an oil change was in order. I drained and sampled the 7 qts of Mobil 1 5W-30. I added LC at inconsistent intervals throughout the past few months. I've sent the sample off to Blackstone and am curious as to the result. Five qts of M1 SL and two quarts of pre-Katrina SM were added along with 4 ounces of LC. Maybe it will be another 10 or more months before the light comes on again. I guess I'll find out how good the OLM is. Any thoughts on how well the oil will fare?