Another oil question... don't shoot me!

[Fourth Horseman]

So I've been running Mobile 1 5w30 since the first oil change at 1500 miles. My question is about eventually going to a heavier oil as the engine ages. Assuming normal operation, no excessive wear and not using oil, should I consider switching to 10w30 at some point?

[RF Overlord]

Fourth:

Knowing the "real" winter temps in SLC, not the fake 60° baloney you tried to con us with last week :P , I think you would not want to use a 10W oil, except in the summer when it was REAL hot, and even then only after you had beaucoup miles on your MM. As others have posted here, the mod motors are designed for thinner oils (CAFE crap aside), and may not take kindly to the extra lower temp thickness. Even my old Buick, with over 176,000 miles on it, gets 10W-40 and it was spec'd for 10W-30 originally. The extra viscosity on the high end helps the oil pressure stay up there after the engine is warmed up, and I only drive the car in the summer (what's the point of driving a convertible with the top UP?).

[vaderv]

Dude 10 30 is not heavier oil.. I just fails to flow at a warmer temp.

[RF Overlord]

Dude, I never said 10W-30 was "heavier" anywhere in my post...

A 10W oil is more viscous than a 5W when compared at the same temp.

From Pennzoil's Data sheet for their Synthetic Blend oils:

Low Temp Viscosity: 5W-30= <6600 @ -30°C
10W-30= <7000 @ -25°C

So, the 5W is less viscous than a 10W...that's all I said.