The "break in" myth is just that, a myth. Indeed, if you drive it like a granny, you WILL have problems.
I've never subscribed to an "easy" break-in. My Uncle, who was a mechanic from the "old school" used to always tell us to do the initial oil change very early, at 100 miles, and work the motor hard.
Indeed, for HD diesel motors, if you don't work the motor near 100% load, the rings won't seat properly.
I've recently come across a VERY touchy break-in guide that makes sense to me. I almost followed this guy's break-in except I did my first oil change at 600 miles, then again at 1,200 miles after 600 miles of heavy towing.
I special ordered a 2000 GMC Sierra with Vortec 5.3 V8 and 4.10 gears. Compared to other GM trucks, mine seems to run a LOT better and gets WAY better fuel economy, all stock too.
I switched to Mobil 1 after the "break-in." Due to my extreme cold winters, I run Mobil 1 0W-30 winter, Mobil 1 10W-30 summer. This April, I'll try Mobil 1 Truck & SUV 5W-40 for summer.
FWIW my oil consumption running Mobil 1 0W-30 is around 1 litre every 6,700 km (1 quart every 4,200 miles). Almost the same running Mobil 1 5W-30.
Running Mobil 1 10W-30, my oil consumption is 1 litre every 11,000 km (1 quart every 6,800 miles). This is amazing compared to other Vortec truck owners, though I consider this to be somewhat high oil use. Next new rig I'll try the controversial "break in secrets."
The URL for that break-in guide is at:
http://www.mototuneusa.com/break_in_secrets.htm
Depending on your climate, I wouldn't be afraid to run either Mobil 1 Truck & SUV 5W-40 or Mobil 1 15W-50. In other countries, Toyota recommends much heavier than 5W-30 and in fact usually recommends to NOT use a 5W-30 in temps over +10 C / +50 F.
Here in North America the dictators at EPA and CAFE tell us what oil to run. They figure instead of allowing an economical turbodiesel like the VW Lupo 3L (Around 100 MPG) they'll squeeze 0.01 MPG across hundreds of thousands of pickup trucks and Ford Excursion V-10's.
A little common sense goes a long way, but try telling that to the gov.
I bought new a 1990 Toyota 4Runner 3.0 V6 and the shop manual recommended a wide range of viscosities. I ran Mobil Devac 1 5W-40 year round except for the 4 years I lived in Salt Lake City when I ran Mobil 1 15W-50 year round.
Compared to other 4Runners the same vintage, my motor was smooth and almost silent. No effect on fuel economy.
Hope this helps.
Jerry
