5W-30 plus 10W-40= 10W-30?

[hamhorn]

I took my '02 Tahoe to my mechanic yesterday and asked for my usual: change the oil with Castrol 10w30 and a Napa Gold filter.

After the fact, he told me he had run out of 10w30 and had used one quart of 10w30, two quarts of 5w30 and two quarts of 10W-40. He said that combination would be exactly the same as using five quarts of 10w30.

Is he correct? I change oil every 3,000 miles, for what that's worth.

 

[CBDFrontier06]

I come up with 8W-34

 

[Hammer]

Quote:

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I took my '02 Tahoe to my mechanic yesterday and asked for my usual: change the oil with Castrol 10w30 and a Napa Gold filter.

After the fact, he told me he had run out of 10w30 and had used one quart of 10w30, two quarts of 5w30 and two quarts of 10W-40. He said that combination would be exactly the same as using five quarts of 10w30.

Is he correct? I change oil every 3,000 miles, for what that's worth.

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essentially, you ended up with a 10w30 that is on the high side of the 30 weight scale. There should be no issues with this mix and I wouldn't even worry about it.

Hammer

 

[Merkava_4]

Based on a 5 quart fill using Valvoline All Climate numbers:

2 quarts 5w30 = 40%
1 quarts 10w30 = 20%
2 quarts 10W-40 = 40%

That puts you squarely at a nice heavy 10w30

 

[JAG]

My hat goes off to you Merkava! That's the way to get real answers.

 

[TallPaul]

Quote:

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I come up with 8W-34

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While such numbers are not defined on the API chart, this is about the size of it. Slightly thinner base oil and a thicker 100C viscosity. You would be close to a borderline 40 weight, but still in the 30 weight category. Still qualifies as a 10W (or a 20W if you want), but likely falls just shy of qualifying for a 5W. Won't hurt a thing, run it if you like.

I may run a brew of 20W mixed with 10w40 for a 15w30.

 

[charbaby]

And if I may add my .02 cents. This may be the best oil change your Tahoe has seen yet! Especially in the heat of Texas.

 

[hamhorn]

Thanks, guys.

Summer in Houston is plenty hot and humid.

 

[Rlc2500HD]

What engine do you have to only have took 5 qts, I have a fleet of LS1s/LS2s and have never had to put less than 6.

 

[hamhorn]

Fair question, Ric. My mechanic topped it off with a quart of NAPA 10w30. I didn't want to complicate my question with the added factor of mixing different brands of oil.

I've read on here that NAPA is made by Valvoline, which, as I've read on here, has a similar additive package to Castrol GTX.

 

[M1Accord]

Why is he dumping various oil into your engine? And what shop still buy their oil by the quart? I would be changing my own oil rather than letting "mechanics" change my oil.

 

[Doc8404]

to get rid of my stash, I'll be running, 2 qts each in the galant:
10W30 (or 40) Chevron Supreme
SuperTech 5w20 conventional

figure in the galant, that can't hurt...she has the widest oil specs i've ever seen...."anything" from 5W-20 to 20W-50

 

[wquiles]

Quote:

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What engine do you have to only have took 5 qts, I have a fleet of LS1s/LS2s and have never had to put less than 6.

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My relatively "small" 4.4L V8 in my BMW 540i takes 8, and my 1995 525i with a 2.5L took 6

Will