In case you haven't heard, a Costco membership could potentially ease the financial sting on your car repair bills. The retailer sells branded tires at wholesale prices, for starters, and its Interstate batteries offer low prices with outstanding warranties. Costco has you covered if you're looking for an oil change, too, since it openly claims that its Kirkland Signature house brand is one of the main perks of being a member. You'll find that label splattered on just about anything, from bath tissues to freaking olive oil. But car lovers would typically have their eye on its synthetic motor oils, and it's not hard to fathom why.
We've already covered Kirkland Signature motor oils, noting that they're either passing or acing the same tests as the other best brands. More impressively, it does this by outclassing its nearest competitors — particularly Mobil 1 motor oils that Costco also peddles at its website – in the all-important savings department. In a mano-a-mano price comparison, you can get two 5-quart containers of Kirkland Signature 5W-30 motor oil at under $36.00. That's about 9.6 liters of fresh oil, which is enough for two oil changes on a standard four-cylinder car.
As for Mobil 1, Costco sells six 1-quart containers of its Advanced 5W-30 motor oil for a total of $39.49, which is about $6.58 per quart. Kirkland Signature motor oils are cheaper while still being on par with the bigwigs in protecting against friction and keeping your engine clean. Knowing this, is it possible you're paying too much for Mobil 1, or are you getting something in return for that decreased amount of oil?
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When it comes to motor oil, there's a choice between semi-synthetic or full synthetic, high-mileage motor oils. There are also purple-colored lubricants (which have a love-or-hate relationship with consumers and actual users) and even specialized diesel oils. Other than choosing between those types, selecting the right oil viscosity is equally as crucial as the API Service Category. When it comes to Kirkland Signature, Costco has 0W-20, 5W-20, and 5W-30 blends that meet or surpass the latest API SP and ILSAC GF-6A standards. That means it's actually pretty good; it proves those oils can slug it out with the industry's finest.
As for Mobil 1, Costco has 0W-20, high-mileage 5W-30, 10W-30, 5W-20, and high-mileage 10W-30 variants. All of these also conform to the latest API SP and ILSAC GF-6A standards. You might pay more for Mobil 1, but you're also paying for claims of the oil protecting engine parts up to 10,000 miles between changes. As you're about to find out, those claims have an element of truth behind them.
Like fingerprints on a crime scene, nothing reveals the truth about motor oil than a comprehensive oil analysis, particularly after spending 6,000 miles inside the engine. Automotive YouTuber Auto Scholar with Mr. B was kind enough to share a laboratory analysis of the oil in his Lexus CT200H hybrid, first with Mobil 1 and next with Kirkland 0W-20 synthetic oil. He took samples after each oil change and sent them to the kindred brainiacs of Blackstone Laboratories.
The results speak for themselves. Auto Scholar broke it down best, but the paper he received indicates that Kirkland is just as good as Mobil 1. The latter had an edge on anti-wear additives like magnesium and zinc, though, which probably explains its hardiness between oil changes. But for some car owners who just want good, affordable oil for their engines, it's hard to go wrong with either Mobil 1 or Kirkland Signature.
Again, selecting the right viscosity is probably more important than branding at this point. But it's comforting to know that Kirkland Signature and Costco are not skimping out on what really matters in protecting and preserving the life of your car's engine.
