What is the meaning of 10W - 40 Engine Oil & Mixed Oil?

Caleen98

Do you mean there is a product labeled "10W - 40 Engine Oil & Mixed Oil"?

If so it sounds like left overs of various oils thrown into a larger batch of 10w40 motor oil.

However, a 10w40 and most any motor oil is going to be a mix of base oils of two or three different viscosities blended, then with appropriate additives likely including pour point depressants and viscosity index improvers to get the end result of the multigrade oil.

TallPaul,

The products are labelled thus,

(1) 10W-40
(2) Mixed Oil

There are two different products.

Please help me explain SAE 10W-40 & SAE 15W-40. Is there any difference between them? If so, what are the differences and which is better?

What is the meaning of Mixed Oil?

Thanks for your help.

Regards

(1)SAE 10W40 and SAE 15W40 is only a measurement of the oils viscosity at two different temperatures. The number in front of the "W" tells us the viscosity at low temperature 10W max. visc. 7000 cP@-25 degrees Celsius.The number after the "W" tells us about the oils viscosity at 100 degrees Celsius. SAE 40 shall be between 12,5 - 16,3 cSt@100 degrees Celsius.
It's important to realise that these SAE spesifications only tell us aboat viscosity, not Quality.
You will find all this for all grades in SAE J300.

I don't know what they mean by mixed oil. As for the 10w40 and 15w40, you can look at the API chart and see the differences, but do those apply in Nigeria? Here is the API chart: API Chart link.

All else equal (and often they are not) I would select the 15w40 over the 10w40 in a hot climate. I can run 15w40 here in southeast Michigan for probably 9 months of the year, but it would get too cold in winter (zero F and lower, approx -20 C). So I run 10w40 because in the summer it rarely exceeds about 90 - 95 F, ~33C). The advantage of 15w40 in a hotter climate is that the base oil generally will be thicker than that of a 10w40.

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I would select the 15w40 over the 10w40 in a hot climate.

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Why? There is no need to do so. I would even recommend to use a 0W-30 oil in hot climates.

If he has established the need to use a 40 weight and there is no winter start considerations, then why wouldn't the 15w40 be a better choice? Assuming all else equal, the 10w40 will have more viscosity index improvers in it. I always thought fewer VIIs was better.

We are talking about 10W-X and 15W-X, X=40. No engine needs a minimum viscosity of 60 or 90 cSt to start.
Otherwise you couldn't start your engine when it's hot. Or are you afraid of starting your engine after filling up gas?

I assume mixed does not imply Part or semi synthetic?

Viscosity choice is interesting

A OW is still thicker at 40c than oils at 100c, so a 0W must flow quicker at start up than a higher W. Making the higher viscosity, unless a synthetic, a problem because more viscosity improvers are required but these shear and shorten oil change intervals or require a higher weight.

Back in the old days the standard oil was 20W50, which probably became very quickly a 20W40 and in a old Mini 20W30.

Today a 15W40 is recommended, I assume the oils today are more stable and also means less shear.
In the UK only M1 0W40 and why not as OW gives flow and 40 protection all year and for up to 2 years.

For race oils the range is from 10W60 a big stretch but the oil has to handle fuel dilution and heat and 0W20 for ultimate performance but still with HTHS of 2.6

The US are tending towards 0W20 for fuel savings but still prefer 3K changes despite probably being easier on the oil, although fuel quality may be an issue and viscosity improvers.

However if oil quality is an issue a 20W50 would give better protection than lower viscosities in warm climates.

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Today a 15W40 is recommended, I assume the oils today are more stable and also means less shear.

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No European Car Manufacturer recommends "15W-40"!
That's no oil quality. That's nothing but an oil viscosity, which says nothing about the performance of an oil.

Callisa,

I drive cars from 70s and GTX 15W40 is now recommended instead of 20W50.

@ MGBV8
I was more referring to actual cars being sold today. In the 60's, they recommended straight SAE 30 oils....