OIL BLENDING CALCULATOR
- Thread starter junebug
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The viscosity of the blended oils is the antilog of the weighted average of the logs of each oil's viscosity in the mix. For a 40/60 blend:
x = antilog { 0.4 Log(a) + 0.6 Log(b) }
x is the resulting viscosity
a is the viscosity of oil A
b is the viscosity of oil B
x = antilog { 0.4 Log(a) + 0.6 Log(b) }
x is the resulting viscosity
a is the viscosity of oil A
b is the viscosity of oil B
antilog you mean e?
antilog is the inverse of log (reversing the log process). On most calculators you can just hit the "Inverse" key, then the "Log" key. You can do the logs in any base, 10, e, or whatever, so long as it's the same base throughout the equation.
You basically are transforming everything to logs, then averaging, then untransforming.
You basically are transforming everything to logs, then averaging, then untransforming.
junebug,
I do a simple linear 'approximation' on the cold/hot weights.
Say I add 5W30 to 20W50 at 50% each...I'll guess I come up with 12.5W40. The weights are actually a range of cSt viscosity so this mix would essentially be a 10W40 or 15W40.
If you mix different ratios adjust with a %. Say 33% of 5W30 and 67% of 20W50, then hot weight = 0.33x30 + 0.67x50. Cold = 0.33x5 + 0.67x50. You can do the math.
I do a simple linear 'approximation' on the cold/hot weights.
Say I add 5W30 to 20W50 at 50% each...I'll guess I come up with 12.5W40. The weights are actually a range of cSt viscosity so this mix would essentially be a 10W40 or 15W40.
If you mix different ratios adjust with a %. Say 33% of 5W30 and 67% of 20W50, then hot weight = 0.33x30 + 0.67x50. Cold = 0.33x5 + 0.67x50. You can do the math.
As an engineer I'm not big on mixing viscosities except when that's all you have and have to add. I am currently running 5 quarts of 5W-30 Maxlife with 1 quart of 5W-30 full synthetic Maxlife in my 2000 Silverado (95K, 5.3L). Pretty pleased with that blend but I don't see a real good reason to start mixing different viscosity oils.
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Originally Posted By: TallPaul
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
Originally Posted By: JGmazda
Originally Posted By: TallPaul
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
Perfect! You may actually have a 15w40 which is even better. I have some 20w that I plan to mix with 20w50 to make a nice 20w40 summer blend.
Originally Posted By: TallPaul
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
Perfect! You may actually have a 15w40 which is even better. I have some 20w that I plan to mix with 20w50 to make a nice 20w40 summer blend.
Originally Posted By: TallPaul
Originally Posted By: JGmazda
Originally Posted By: TallPaul
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
Perfect! You may actually have a 15w40 which is even better. I have some 20w that I plan to mix with 20w50 to make a nice 20w40 summer blend.
Thanks! I live in Phoenix and during the summer my oil pressure goes down a bit in the high heat. Thanks to this forum, I started to mix. I wanted to stick with Valvoline since for most of the year I use Maxlife full synthetic. Doing my first UOA on that this week. Will post the results. 15w-40 sounds great for my car. Thanks Paul!
Originally Posted By: JGmazda
Originally Posted By: TallPaul
The blender that makes the oil you buy already has mixed viscosities, so I see no problem further mixing viscosities.
Good point. I just mixed 2 quarts 10W-30 with 2 quarts 20W-50 Synpower. Why? They don't make a 10W-40. I wanted this grade and the Shell calculator said I'd be approx 14cst at 100C deg. I don't see the harm in it.
Perfect! You may actually have a 15w40 which is even better. I have some 20w that I plan to mix with 20w50 to make a nice 20w40 summer blend.
Thanks! I live in Phoenix and during the summer my oil pressure goes down a bit in the high heat. Thanks to this forum, I started to mix. I wanted to stick with Valvoline since for most of the year I use Maxlife full synthetic. Doing my first UOA on that this week. Will post the results. 15w-40 sounds great for my car. Thanks Paul!
A maybe even better mix would be Maxlife Full Synthetic 10w30 with Synpower 20w50, but I'm sure your mix will perform quite well.
I was thinking about that too. I wish Valvoline would introduce a 10w-40 in their Maxlife Full Synthetic. Based upon 50% ratios of each... do you think that would work out to be a 15w-40?
Isn't Synpower pretty much the same oil without seal conditioners?
Isn't Synpower pretty much the same oil without seal conditioners?
The 10w and 20w probably will work out to 15w more or less.
Ask Valvoline tech folks about the relation between Max syn and synpower. Seems reasonable that they share some basic components. While you have them on the phone ask about 10w40 or better yet tell them to make it in 15w40.
Ask Valvoline tech folks about the relation between Max syn and synpower. Seems reasonable that they share some basic components. While you have them on the phone ask about 10w40 or better yet tell them to make it in 15w40.
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