350 SBC with mild rebuild...nothing crazy. New crank, mild cam and heads by the guy I bough it off of. About 700 miles now on the re-build What type of oil should I put in the crank? I have been running Castrol 10w-40, with STP oil adderr...the sticky, thick stuff. Running About 40#'s at cruzing speed when warmed up,20/25# at idle.

I've seen some posts with 10w-30?

Thoughts?

Yikes, 10-40 AND STP...... so during the rebuild what clearances were set up on the rods and mains? With 10-40 and STP I'd think it would be off the charts when cold. My guess is that if you go to straight 10W30 your pressure will be 10psi at idle, warm. While that "meets specs" a tighter clearanced engine will normally idle at 20 psi warm on 10W30 and cruise at 45psi with a standard pump.

CLEAN oil. Shouldn't need additives. I like synthetic. Have used Castrol Syntec and Mobil 1, both with good success.

Thanks guys for the feedback....I am going to move to 10w-30 with no STP and monitor the PSI to be OK.

Originally posted by drielly:
Thanks guys for the feedback....I am going to move to 10w-30 with no STP and monitor the PSI to be OK. Not sure I understand that.
Why not just run 10w-40 oil and no additives?

he might be having a hard time finding synthetic 10W-40.... i know i couldn't find it locally so i just went with 10W-30

just my 2 cents

all you need is 20w 50 or 10w 30, no synthetic. Valvoline is good stuff. I use either that or Kendall.

Mobil 1 10w-30

Originally posted by chev65elleSS:
all you need is 20w 50 or 10w 30, no synthetic. that's the debate of the century..... personaly i use Mobil 1, not because i "think" it's good, but after running an oil-cooled road race bike for 50k miles without a rebuild, and also i experimented with regular oil (burnt after 100 miles in that bike) and Mobil 1 (burnt after about 1k miles) i was convinced...... for as little miles as we put on our cars, the extra $20 per oil-change to me is cheap insurance.

153K miles on '93 Jeep Grand Cherokee
167k miles on '88 Old Delta '88
99k miles on '99 Grand Am
143k miles on current '97 Jeep Grand Cherokee

10w30 or 10w40 Valvoline in every one of them. Never a problem!

Brian

I have ran Walmarts, el-cheapo, Tech2000 oil and filters in our cars and the old Astro Van we no longer have for more years then I care to count!!!

Never had a problem!!

I also put a half bottle of good old "snake-oil" named "Marvel Mystery Oil" in my oil at change and the other half in the gas tank every so often b/c it is TO ME an excellent, old fashioned top-oil product that helps keep both the oil side and the air/fuel and combustion side clean.

I just add the MMO on top of the full oil change and don't worry about going over the full mark and dump the rest in my gas tank when I fill her up...

pdq67

PS., I will say that the 5w30 stuff threw me for a loop when I started using it b/c I was ALWAYS a 10w40 summertime/10w30 wintertime oil sorta guy...

I put some 20w50 in my '87, Chevy Sprint ER 3-banger corn-popper one time in the summer and could tell the difference in lost power. I ran it for about 4,000 miles during the hottest part of the summer and then went back to the 10w30 stuff for summer and 5w30 stuff when it got cold!!!

I've always thought MMO was automatic transmission fluid, ATF is full of detergents to keep stuff clean.

Nope! Top-oil lube!

Bardahl used to sell a top-oil lube too..

I don't know if they still do or not??

pdq67