Lubrication Expert Sees Just How Accurate GM’s Oil Monitoring System Is
An expert in vehicle lubrication compared a used oil sample to GM’s oil life indicator to see just how accurate it actually is, according to a report from Motor Biscuit.
Besides being the son of former NASCAR driver Lake Speed, Lake Speed Jr. has held certifications from the Society of Tribologists and Lubrication Engineers as a Lubrication Specialist and Oil Monitoring Analyst for over a decade. On his YouTube channel, The Motor Oil Geek, he recently delved into GM’s oil life monitoring system.
The software that determines oil life was first designed around 40 years by three GM engineers: Donald Smolenski, Paul Harvath, and Dr. Shirley E. Schwartz. The algorithm they created was based on the OnStar systems found in Cadillacs and Corvettes at the time, and takes into account engine behavior such as cycle length, fuel injector fires, and water temperature.
Since the 80s, GM has implemented the technology in all their vehicles, with Ford and Honda having their own versions of it—but there are some automakers you won’t see this system with, like Toyota, Nissan, or Subaru.
The test vehicle, a Cadillac SUV, last had its oil changed between 5,000 and 6,000 miles ago. When the dash said there was 9% oil life remaining, Speed popped the hood to obtain a sample for himself.
The viscosities were in spec: Dexos 1 5W-30, with an oxidation value of 13.2. Far from the end of its life.
“It’s very conservative,” observed Speed. “Even though it says only 9% oil life left, at 13.3 oxidation value, for a Dexos oil, we’re not even close to the end of life yet.”
Does this mean the oil life indicator is indeed inaccurate? Not necessarily. Speed contended that this is a deliberate design choice on the part of the automakers, aware that many drivers are likely to push their oil life closer to zero before they even consider taking action.
“Now I’m not saying you should go over the oil life indicator—I’m just saying that this tells you accurately how far you can go safely,” surmised Speed.
