Engine break-in oil

[wmc2004aug at bellsouth.net]

At 04:21 PM 9/6/2004, you wrote:
>What type of oil do you recommend for breaking in a freshly rebuilt
>SR20DET?  Some sources say to use non-detergent straight 30 weight oil to
>help the rings

I've never built an engine from scratch.  But reading for 20 years or so,
and comparing opinions on the 'net for over 10 years, here's what I'd do
for a street engine if I was building one tomorrow:
* Fill with cheap shit 20 or 30 weight and run for about 15 - 20 mins,
flushing out the assy lube and other gack.
* Drain and refill with same.
* Drive it like I stole it for a hundred miles or so.  Change oil at about
1000 miles with decent stuff, eg: Castrol.
* Switch to Mobil One around 20,000 miles.

I've long suspected the "break it in gently" was bull shit.  This guy agrees:
http://www.mototuneusa.com/break_in_secrets.htm

>I was thinking of using either Castrol GTX 10W-40 or 20W50. What do you
>guys think?

Too heavy.  For break-in, or regular use.  If you built the motor to
factory specs, the clearances are very tight.  Lightweight oil, like 5W30
or 5W40 won't build up as much pressure, but will flow a much higher
*volume* which the motor likes.

    -Wayne    '93 SE-R / '93 NK2k / '91 NX2k / '90 Miata