Afm Help Needed

[HuntingEd]

Ok so i normally run 15w-40 in all my trucks, mostly cause 1/2 are diesel and I buy it by the drum, so i run it in all my gas vehicles as well. But now ive got the new 6.0LVmax w/ active fuel management. According to what I've read i need to use 5w-30 in my truck. I hate to go w/ a lower grade oil for engine life sake, but i think i have to.

 

Anybody know if I can run a different grade oil and not screw up the on/off soleniods for AFM?

 

Also, if im forced to go w/ 5w-30 im probably gonna use a synthetic, probably Mobile 1. Think thats ok? or am I foced to use dino?

 

Thanks,

Ed

[GeoHawk]

I would say go with the 5W-30, dino or synthetic shouldn't matter. Since AFM uses oil pressure to control the operation of the deactivated cylinders' lifters, going with a thicker oil would likely have an effect on its operation. From GM Powertrain:

 

Valve lifters are operated by the engine’s camshaft, and lift a pushrod that operates the valves in the cylinder head. In the Gen IV Vortec 6.0L, the De-ac lifters are installed in cylinders 1, 4, 6 and 7, while the remaining cylinders use conventional lifters. The hydraulically operated De-ac lifters have a spring-loaded locking pin actuated by oil pressure. For deactivation, hydraulic pressure dislodges the locking pin, collapsing the top portion of the lifter into the bottom and removing contact with the pushrod. The bottom of each De-Ac lifter rides up and down on the cam lobe but the top does not move the push rod. The valves do not operate and combustion in that cylinder stops. During reactivation, the oil pressure is removed, and the lifter locks at full length. The pushrods, and therefore the valves, operate normally.

 

The final AFM component is the LOMA. This cast-aluminum assembly is installed in the Vortec 6.0’s V, or valley, in place of a conventional engine block cover. The LOMA holds four solenoids, control wiring and cast-in oil passages. The solenoids are managed by the ECM, and each one controls oil flow to a De-Ac Lifter, activating and de-activating the valves at one cylinder as required for Active Fuel Management.

 

The Gen IV Vortec 6.0L’s fuel injectors are identical for all cylinders; those feeding the de-activated cylinders are simply shut down electrically by the ECM during de-activation. When the cylinders are deactivated, the engine effectively operates as a V4. AFM operation is load based, as measured by the ECM using dozens of inputs, overlain with the driver’s demand for power as measured by throttle application. AFM’s response time varies with oil temperature, but in all cases is measured in milliseconds. Operation is always transparent to the driver. The engine returns to V8 mode the instant the controller determines that acceleration or load requires additional power

 

Since oil temperature (hence oil pressure) affects AFM operation, I would surmise that a higher viscosity oil would affect it as well. 5W-30 will be just fine for your engine. My '03 has had dino 5W-30 in it since new and after almost 120K miles, the used oil analyses still come back normal.