Double:
Some data would help understand. This is Good information ! thouh I am sorry for your result.
What oil and engine?
Also commute length and average speed?
BTW I live just a bit North of Haverhill Mass.
That's funny, we probably are neighbors then.
The car was a 2007 Lexus LS460. Purchased in great condition with 70,000 miles off a Lexus technician I knew.
I initially did 5,000 mile oil changes using Mobil 1 synthetic 5w20 for 5,000 mile intervals. I swear to god that car didn't use a drop of oil. Then at 90,000 miles I began trying extended drains (because of recommendations from people that were doing the 10,000 mile oil changes suggested by Toyota).
So I went ahead and did 7,500 mile oil changes at first, using Mobil 1...I noticed that the car would not use a drop up until 4,500-5,000 miles, but after that it would (might use a quart between 5,000-7,500). Thought that was strange.
Then I switched to Toyota Genuine Synthetic 0w20, same thing happened.
Then I tried the Mobil 1 Extended performance oil, and tried to go 10,000 miles...added around 2 quarts. At this time I'm nearing the 120,000 mile mark of ownership. I decide to switch to a 0w30 Mobil 1 oil, but there's no improvement, it's gradually getting worse (using around 2 quarts in 7,500 miles now). Then I switched to a Napa house synthetic (5w30), started using more oil. At 150,000 miles or so I switched back to 5,000 mile intervals and was using around 2 quarts in between. Then at around 160,000 miles I began using Castrol Magnetic 5w20. Used maybe only a quart in 5,000 miles, but the next time I used it it was 2 quarts. By the time I reached 170,000 miles it was drinking oil. A quart or more every 1,000.
Inside the intake manifold you could see the oil tracking. The spark plugs I pulled were soaked with oil, not the threads but the plugs themselves. If I stepped on the gas hard, there would be a big puff of smoke.
My driving style/commute, was basically a piece of cake...easy up and down 495 or 93, commuting, going between 65-75 mph. Very little stop and go traffic. No city driving. All easy highway....600 miles a week, every week. But like I said, maybe it wasn't the extended drains? I don't really know, but I suspect it was.