Can you mix two different weight Mobil 1 sythetic oils?

According to Mobil's website, it is OK to mix 2 different viscosity's of Mobil one as they are completely compatible. There is no way to know exactly what the final viscosity is though, short of testing.

Not sure where you're located geographically mbl, but going into the summer, that weight oil and those oil pressures seem absolutley fine to me. I wouldn't change a thing. Now when things cool off in the fall, I'd want to drop it back to 10W30 or 5w30 depending on the low temps you see. Most folks on the site would LOVE to have your idle and cruise oil pressures.

Michael Yount said:

Not sure where you're located geographically mbl, but going into the summer, that weight oil and those oil pressures seem absolutley fine to me. I wouldn't change a thing. Now when things cool off in the fall, I'd want to drop it back to 10W30 or 5w30 depending on the low temps you see. Most folks on the site would LOVE to have your idle and cruise oil pressures.

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"Most folks on the site would LOVE to have your idle and cruise oil pressures"

I KNOW!!! idle 10 psi.. cruising every 1k, 10 psi more... when it's cold around 70 psi.. but i use 15-50 Valvoline, normal oil...

I wouln't think the synthetic mobile 1 15w-50 would gum anything up.

You might gain a bit of power with a lighter viscosity - but not enough to notice in day to day driving. For a dedicated race-only car in a tightly controlled rules class where every 1/2 HP makes a difference - yeah, run a lighter viscosity oil provided the pressure doesn't dip too low. But on a street car - not sure what technical term 'gummed up' is equivalent to; and your pressures are fine. Leave it alone til winter; then go with a bit lighter visc. to ease cold starts.

i agree with everyone. the power loss thing is negligible, as said by Michael (it is there, but on a street driven car (read: not a track queen), you wont feel it, and would only see it while racing in conditions like Michael mentioned.

also, with a blower, i would not even worry about it. the blower makes it a moot point when talkin about power loss. people who told you about the power loss are theoretically correct, but practically speaking for a blown street car, you wont notice. i would prefer better protection at higher temps.

M1 tends to be thinner than a same viscosity dino oil. if you notice it taking a while to build up pressure when started in the morning, then do something. that weight of M1 has pretty good pour points and cold flow ratings.

also, synthetics clean things up, not gum them up (unless they were referring to the by-product of the detergents - removing crud and sludge). if so, i would have worded it differently.

good luck.