Join Date: Oct 2005
Location: Eastern VA
Feedback Score: 0 reviews
More bad information... 15W40 is good down to 5 degrees
On paper yes, in the real world no! 5w40 synthetic is a much easier start on the injectors, starter and batteries (and intimately the FICM because the batteries wear out faster). Repeated cold start wear over time has proven to cause problems with the injectors of these trucks.
While I don't have a study to prove this, all you have to do is listen to a low temp cold start of these trucks with the two different oils in them to tell the difference. Experience gained over time shows that the 5w40 helps with injector life. It may be anecdotal evidence, but the consistence and number of the reports tends to prove the theory.
2006 F250 Lariat Supercrew, ESOF 4x4, 18" tires, FX 4, HD Alt., block heater, Integrated Trailer Brake Controller, Upfitters, power rear window, cab lights - delivered 10/25/05
Ford Remote Start; High idle mod; Timbren load levelers, Scangauge II, Blue Spring upgrade, Quick Start 200 amp large frame alternator, 2 batteries January 2010; GPCM replace October 2011; 2 EGR valves; EGR Cooler replaced 12/30/11; Performance Machine & Mfg. coolant filter added 1/2/12; Rotella T6 5W40 oil; turned rotors, replaced brake pads for 1st time 1/7/12 101K miles; GPCM, both subharnesses and all 8 glowplugs replaced 1/5/13 at 118,000 miles; 2 Ford batteries replaced under battery warranty twice, the latest 9/18/2015; FICM power supply board replaced with Dorman board 11/20/13. Coolant flushed and replaced with Prestone ELC 9/27/14. STC fitting 10/19/14; Dummy Plugs 11/8/14; Turbo rebuilt 11/29/14; cold side CAC tube and boots replaced with metal tube 1/24/15.