2010 GMC Terrain Long-Term Road Test


2010 GMC Terrain: Collecting an Oil Sample for Analysis

September 19, 2010

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The last time a dealer laid hands on our 2010 GMC Terrain, they put a sticker on the windshield reminding us to come in for our next change at 3,000 miles or 3 months. Wrong!

Modern cars and the modern oils they run don't need such frequent changes. And this very GMC Terrain has a built-in oil life monitor that tells the driver exactly when the next change is due, right on the dash. And the calculation it makes is based on driving style and conditions, not straight time or mileage. Our dealer's scare tactics are nothing more than attempt to get into our wallet.

At the same moment our Terrain's oil was 4,000 miles old -- 1,000 miles past the dealer's "recommendation" -- the Terrain's own on-board oil life monitor was telling us the oil still had 60% of its life left. In other words, a 10,000 mile oil-change interval was going to be cool.

Since then, the Terrain has been on some easygoing road trips. With 5,731 miles on the oil, the oil life monitor now says the oil has 48% of its life left. The projected oil life is up over 11,000 miles because of our recent light-duty use.

But does the oil life monitor really have things all figured out? Will this oil still have what it takes 5,000 miles from now?

I decided to pull a sample and send it to a laboratory for analysis. Blackstone Labs in Fort Wayne, Indiana will do it for between $25 and $35.

The standard $25 test tells you how your engine is doing, based on an analysis of the metal and "insolubles" in the sample. A worthwhile option is the $10 TBN or Total Base Number test. This is the test that measures properties related to oil life.

It's clear that we have time on our side. Before we change our Terrain's oil, we're going to send a sample in for a TBN test. Here's how we pulled the sample you see above.

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The bottle on the right is the sample bottle. Well, not the sample bottle; it's the shipping bottle. The sample bottle is inside, like those Russian nesting dolls. This is what you get if you take Blackstone up on their offer for a Free Test Kit. We'll see more in a moment.

On the left is an oil extractor. You don't need this, but it sure helps. Blackstone will sell you one for $30, and with it you can withdraw the oil straight up the dipstick tube. The sample only amounts to 3 oz, so almost all of the oil remains in the engine. This is the way to go if you want to do TBN test mid-stream, like I'm doing here.

Without one of these, you instead take the oil out of your drain pan when you change your oil. That's messy, and the results won't have any bearing on how much longer the oil will last, because, well, you already drained it out. Classic moot point, that is. A TBN test will still help you decide how much longer to let your new oil stay in, though.

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There's a lot of stuff inside the black mailing bottle: the 3 oz sample bottle, an absorbent pad in case it leaks, a zip-loc to further contain that, some paperwork for you to fill out about the oil, your engine and your car, the address where you want the results sent, and how you're going to pay for the test.

This is what you'll receive when you send in for the free test kit. Note that they'll send you the kit for free, but the analysis will still cost you $25 when you send the sample back.

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Pull the dipstick out, slide the extractor's hose in all the way to the bottom, then pull it back up about a half-inch before you start.

The engine must be off, but it's best to begin within seconds of shutting it down. The oil needs to be warm and, more importantly, recently circulated so any particles are still in suspension. Don't wait any more than a few minutes. I did this at the gas station while the gas was going in. And I finished taking the oil sample before the gas tank was full, too.

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With the sample bottle attached to the extractor, simply pull gently on the handle to vacuum out the oil. Go slow, don't overflow. The vacuum pump won't force oil back down the tube if you need to stroke the handle a second time.

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It's best to fill it about this full. Blackstone needs a certain amount to run all of their tests. Also, a fuller bottle doesn't slosh about.

This matters because the post office might turn up their nose at the sound of sloshing liquid. Blackstone says it's legal to ship motor oil through the mail in small quantities for analysis. They say the black bottle with the secondary bottle inside meets the regulations. They provide downloadable documentation on their website to show your postal agent if they still refuse the package.

But the folks I've met ay my local post office don't seem to respond well to sloshing sounds, the black bottle or the letter. Near as I can tell, they seem to think the black bottle is the ONLY bottle, perhaps because they can't see the secondary packaging inside. I've found it easier to put the entire package (sample bottle wrapped in absorbent pad, stuffed into ziploc, stuffed into black bottle) into a small box or cardboard mailing tube to avoid misinterpretation.

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Finally, the paperwork. This gets stuffed into the black bottle, too. Outside the ziploc is best, I think, to guard against the unlikely small leak.

Blackstone turned this around quickly when I did this to my minivan. I got the results in a couple of days.

I expect to know something about our GMC Terrain's oil later this week.

Dan Edmunds, Director of Vehicle Testing @ 15,346 miles

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Edmunds Insurance Estimator

The Edmunds TCO® estimated monthly insurance payment for a 2010 GMC Terrain in VA is:

$113 per month*
* Explanation
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