"Blending" Oils

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Sep 27, 2003
Princeton, TX
We recently purchased a Hyundai Santa Fe with a 2.7 L V6. I started running M1 10W-30 and so far have been happy. The owners manual gives the option of running thicker oil in the summer (I live in Dallas, TX...so it's hot here in the summer).

My question is, should I continue to run the 10W-30 year round? Add 1 or 2 quarts of M1 15W-50 in the summer time? Or just run M1 15W-50 in the summer and 10W-30 in the fall, winter, and spring?

Is mixing 10-30 and 15-50 ok as long as you use the same brand? What would the weight of the oil be if you use 4 quarts of 10-30 and 1 quart of 15-50?

Brian Miller
For Austraila, the recommendation from Mobil is

Mobil 1 10W-30 or Mobil Synth S or Mobil Super S or Mobil 1 5W-50

So I'd say that 10W-30 or 15W-50, or anything in between is gonna do alright.

Call it even, and go 0W-40.

[ October 27, 2003, 04:12 AM: Message edited by: Shannow ]
I mixed the 5W30 and 15W50 in equal parts for a few changes and liked it. Now that the 0W40 is out I just use it.

Mobil told me that I could mix there oil until ny heart was content and not hurt a thing.
When I ran M1 in the Wifes Sante Fe, I mixed 1 quart 15w-50 with the rest 10w-30. mathematically it came out to a 11w-35, and seemed to work well in the sweatbath of Arknasas....
I mixed 5w-30 with 0w-40, and have had "mixed" results. For the first 1000 miles, my truck ran great. Smooth start-up and smooth hwy running. Now it starts smooth, but vibrates when warm. I think my mix is extra unstable. It must have sheared down quite a bit. My recomendation is to stick with one grade & brand.
You can't mathematically figure based on the SAE numbers (10w, 30, 50, etc) as they are groups representing viscosity ranges and the ranges vary and the particular oils vary within the group. Mixing 5w30 equal with 20w50 may come out to a 10w40 or a high 10w30, but you will have a dumbell oil, that is bimodal with the base oil molecules clustering in the 5w range and the 20w range. This may be fine, but without testing, you would have more confidence with a straight 10w40.
If the owner's manual gives the option of running a thicker oil, then by all means
"load-up" to the higher vis for summer.

[ October 27, 2003, 12:13 PM: Message edited by: MolaKule ]
Thanks for all the responses. I'm still new at this!

My question is: Being that I'm in Dallas, TX (hotter than h#LL summers, and fairly cold, short winters), should I continue to use the 10w30 M1 year round, or go with the 0w40 M1 year round? I don't really like the idea of a "0" oil! And what about the spread; 0 to 40?

Right now, I'm leaning towards the 10w30!

Any comments would be greatly appreciated,
Brian Miller
If you are going to listen to anyone on this board, listen to MolaKule..and he said to use the thicker oil.
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