First, cold lubricant (oil) viscosity may be too high to properly lubricate some parts, causing premature wear. Second, the injection system delivers more fuel for better driveability when cold, which can wash lubricants from the cylinder walls. Third, critical engine clearances change to their engineered optimal level when normal thermal expansion occurs. (that's a GOOD thing ;-).
Jim O'Neill - Chino Autotech Inc., Auto Club SoCal AAR
SAE Int'l SoCal Section Board of Governors,
Vice Chair, Service Technology Programs
NASTF Service Information/Communications Committees
Auto Value/Bumper-To-Bumper CSC Nat'l Council
ASE CMAT-L1, CA. Smog Check Technician
AMI AAM Accredited Automotive Manager