Originally Posted By: Jim Allen
Originally Posted By: gathermewool
Hydraulically operated systems can't be THAT sensitive to viscosity. It just doesn't make sense that oil wouldn't flow through and pressurize the applicable mechanism as soon as the solenoid energizes.
I think you are right... and I confirmed it in at least one case.
I have a 5.4L Ford V8 with VVT. I was considering carefully a viscosity change to a thicker oil. I wasn't doing it because I'm a "thick oil guy" but for other reasons I won't go into now. My big research stumbling block was to determine the precise effect on the VVT, as that is one of the cautions most often presented. I couldn't get that question answered by anyone, so I answered it myself. Since I have a programmer with a datalogging capability, I datalogged cold starts and normal running with 5W20 and then with the 10W30 I installed
later.
Bottom line, I couldn't tell the readouts apart but for a couple of very tiny data point differences here and there ... eg normal noise. In the case of my Ford, the VVT doesn't begin to operate until the oil temp has reached a certain level anyway. I concluded the change in viscosity from a 5W20 syn to a 10W30 HDEO mineral had virtually no effect on VVT operation I could see. I've been
running the 10w30 oil now for 19 months and about 12K miles. I usually have the cam timing PID up on the screen of the programmer, mainly because I discovered it was a great way to observe engine load and drive more economically (cam timing stays advanced= light load) and I haven't observed any glitchy behavior vs when I had 5W20.
I can't speak to the other VVT engines out there. Perhaps some might not react
well to visc changes. Ultimately, it's up to the owners to determine, as I did, the efficacy of a change, either by research or direct observation of whatever instrumentation can be brought to bear.
I'm part of a hemi forum and I've learned that the cylinder deactivation is done with oil keeping the intake valves closed on the deactivated cylinders.
There is a member there who pushes the 5w-20 on everyone claiming the cylinders won't deactivate properly blah blah blah so one member did as you have and datalogged using 5w40.
Turns out that the cylinder shut down was unaffected,since it too is controlled once oil reaches the right temp which at highways speeds is mere moments.
I've also heard the vvt whine in the mustang forums claiming thicker oil affects it however in the real world the difference is imperceptible.
I saw a post the other day that I think should be the quote of the year. It went something like "engines are designed to run on a variety of oils and manufacturers spec whatever is readily available in each market"
I think that statement is closer to fact than I know.
Merry Christmas.
