WD-40 does work but you almost need someone to crank while you're spraying it. I used to do that with the old Ford with the 6.9 IH in it that I had...... it was hard to start below 40 degrees even with good glow plugs.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k