I paid for an oil analysis this time, so I thought I would share the results. I am not recommending anything, just sharing the relevant information.
2006 2.2 ecotec engine without variable valve timing. Similar engine to the 2.4.
Feb 1st, I changed oil using 5W 30 Motomaster Supreme API SN GF-5 [cheap] Conventional oil.
Installed Fram oil filter CH9018
Air filter is old.
The oil was in the car until July 12th and covered a distance of 7,700 miles, during which time no oil or additives were added.
The OLM counted down to zero about a week before I changed the oil. It did not count down to a negative number but I estimate it should read about minus 5.
Three different drivers drive this car. The overall driving style was a little on the conservative side.
Temperatures ranged form a month of 30 F mornings starts in February to the last month of 90 F. summer days.
A/C used for perhaps 6 weeks.
I guesstimate the driving was 50/50 highway/city. Some short 1 mile trips and some 2 hr expressway runs and everything in between.
When I drained the oil it looked dark amber, not black. It felt slippery and smelled good....mmm. But what do I know?
The way I read this report tells me the oil has done an excellent job of protecting the engine so far but now the additives providing protection against acid build up [TBN] are all but gone.
Used Blackstone labs in Indiana. And used their TBN test for an extra $10.
Tests cost $45 with shipping. I must have more money than brains.
If I am going to shell out this money, others may as well get to read it.