Guys, My buddy has a 2005 Lincoln Aviator with 135,000 miles on it. After driving for 5K miles, his oil was below Low. No leaks. His V8 just must burn a lot of oil. Do you think he should stick with plain Jane Mobil 1 Full Synthetic or make the switch to Mobil 1 High Mileage? Your thoughts and or oil recommendations are welcome. Thanks!