2010 GMC Terrain: Can You Trust Mr. Goodwrench?
September 03, 2010
This GM Goodwrench maintenance reminder sticker appears on the windshield of our 2010 GMC Terrain. As you can see, it's telling us that the next service is due at 12,615 miles or Sep. 30th, (whichever comes first, presumably), at which time we'll need to change-out the 5W30 motor oil.
I asked Mike to check our records, "When was the last oil change?"
"June 30th at 9,615 miles," said Mike.
You don't need a calculator to figure out that works out to EXACTLY 3 months or 3,000 miles.
I glanced at the odometer. It read 13,636 miles, just about 1,000 miles over. We've got just over 4,000 miles on this oil. Mr. Goodwrench will not be pleased.
Then I fiddled with the Terrain's multi-function display and found the Terrain's oil life screen.
As you can see, it indicates that 60% of the oil's life remains, which means only 40% has been used up over the 4,000 miles since Mr. Goodwrench last laid his wrench on it. You don't need a calculator (well, maybe you do, but I don't) to see that it will take 10,000 miles, 6,000 miles from now, for the oil to be 100% spent.
What's up with that, Mr.G?
Page 9-12 of the Terrain's owner's manual describes how this so-called "Engine Oil Life System" works.
"This vehicle has a computer system that indicates when to change the oil and filter. This is based on engine revolutions and engine temperature, not on mileage. Based on driving conditions, the mileage at which an oil change is indicated can vary considerably."
OK, that takes care of miles, but what about time?
"It is possible that, if driving under the best conditions, the oil life system might not indicate that an oil change is necessary for over a year. However, the engine oil and filter must be changed at least once a year."
So 3,000 miles is bogus, and 3 months is also bogus.
Who are you going to believe? Do you go along with the oil-change industry, represented by oil refiners, oil filter makers, quick-lube joints and, apparently, GM's own Mr. Goodwrench? Or do you trust the GM engineers who designed the GMC Terrain's engine and its Engine Oil Life System and then warranty said powertrain for 5 years or 100,000 miles?
I'm an engineer. You know what my answer is. I'm not changing the oil just yet, and I'm going to peel off that sticker. The Engine Oil Life System will toss out a warning when the oil has 600 miles left.
Maybe GM ought to have the HR department talk with this particular Mr. Goodwrench guy because, frankly, he can't be trusted and he's attempting to rip people off and/or he doesn't understand the workings of the very cars he's supposed to repair. Either way, his actions are negating the beneficial effects of one of our GMC Terrain's most useful built-in features.
Dan Edmunds, Director of Vehicle Testing @ 13,636 miles
PS: Perhaps this Mr. Goodwrench should read this...
GM's Corporate Goodwrench Stance on Oil Change Intervals http://www.goodwrench.com/Services/OilChange.jsp