I know this has been discussed a million times,

I am running a 350 with vortec heads, LT4 hot cam. I turn the motor up to about 5400. Currently running 15-40 Mobil diesel oil. I am going to switch to mobil 1 synthetic.

Bearing clearances around .00025 mains, .00020 rods.

Do you think 15w-50 is too heavy? Is 10w-40 too light? Those are the only to that are available at my local walmart that are close to what I want.

Thanks

Get ready for a million replies,

If it's a roller cam Mobil 1 15w-50 is the cost effective (Wally Mart) choice for a high performance oil.

If it's not a roller I'd use the Kendall 20w-50 (hi ZDDP), another value at AutoZone.

Yeah it is a roller. Used Rotella in the non roller motor.

I know there is a ton of opinions on brands and such, I was only looking at the weight aspect of it. Don't want to be too thin for harder running, nor to thick for bearing clearances and hydraulic lifters.

I ran Mobil 1 15w-50 in my ChrisCraft Stinger (modded 350s) and am using 25-40 MerCruiser full synthetic in my Fountain 6.2s.

I run valvoline vr1 50w racing oil in mine and have for years and it works perfect so far.

If you are having good luck with the 15-40 why not stick with it ? Mobil 1 has a 15w40. If you cant find the 15 40 then the 10w40 will work just fine. The "40" number is the hot viscosity and it will be the same in both of them.

Thanks for the input guys. Went with the 15w-50. I would have stayed with the 15w-40 but they didn't have it available in synthetic.

I run Amsoil 10w30 Dominator in my 700hp BBC and my pressure never drops below 20psi at 650rpm idle and that's after running wide open for 10 miles. Your clearances are tight, you're loosing hp to viscosity sheer and pushing more oil past the pump bypass than you need to.