Should I believe my cars oil life monitor?

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Nov 13, 2003
Albuquerque NM
Switched from synthetic blend to Amsoil in November. Before switching I would change the oil when the oil life monitor read 50% which was typically 4000-5000 miles. After switching to Amsoil the car is at 5% after 4000 miles. Any suggestions? BTW the synthetic blend was Valvoline 10/30
The OLM has been designed for Dino. Should we believe in it ? Wait 1 weeks and I will post 2 oil analysis for 1 vehicle with 6500 miles of highway use and changed before the light goes off. And one vehicle with 2500 miles of short trip in Canadian winter with the OLM at 38%. Furthermore this vehicle ran cold for over a month, wife didn't know better ( thermostat b/o)
The car is a 2000 Grand Prix GTP (supercharged 3.8) with 42k miles. We bought it with 18k and had only run Valvoline Durablend 5w30 until Nov. when I switched it to 5w30 Amsoil. My main concern is that the oil life monitor went down twice as fast with the Amsoil as opposed to the blend
I may be mistaken, but I don't think the GM oil life monitor "knows" what kind of oil is in the engine. It determines intervals based on a number of operational variables and is considered safe when used with dino oils. The assumtion is that a quality synthetic will always last longer than dino giving you some safe margin for error if you just change when the monitor tells you to change... The technology does not actually monitor any single quality or physical property of the oil. Instead, the Oil-Life System monitors engine revolutions, operating temperature, and other factors that affect the length of oil change intervals. Did you reset the monitor after your last oil change? If not, you're still reading a continuation of the previous interval... [ March 31, 2004, 06:29 PM: Message edited by: jsharp ]
[Cool] There are posts regarding how the OLM's work elsewhere here. Possibly it went down faster because it was winter. Not sure how cold it gets in Albuquerque. I think some of the OLM's go by how much fuel got burned and not how many miles and in winter that will be more. My wife does a 50 mile highway round-trip to work every day and hers goes off right around 4800-5300 miles every time. I could be wrong, but I find it hard to believe that the OLM knows what kind of oil you have. Personally, I would only go by the OLM if I was running full synthetic.
MY experience only shows that the OLM setting is way too optimistic. I really wanted to believe in the system , but my latest oil analysis posted shows that I wasn't doing anything good to my van and cars. See for yourself in the UOA section. I will go back to a more realistic interval like 5000 miles for my commuter car, and 3000 for my van mostly driven in town for short trip and both followed by a UOA.
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