Verted

Exactly!

It's our religion. Nevertheless, common sense still tells me that 5W-50 Full Synthetic Motor Oil is better for our 3Vs than 5W-20, as I did not purchase a Mustang for fuel economy. Roush does not specify 5W-20. Even Ford specifies Motorcraft 5W-50 Full Synthetic Motor Oil for its 4V Shelby GT500. So 5W-20 it is; for me and for you.

theedge67

I tried using Amsoil 0W30 in my GT and had the oil analyzed twice with similar results. It showed a little high on the wear metals, definetly higher than I expected with a quality synthetic, but still within acceptable ranges. I then switched to 5W20 Mobil1 and had it analyzed again, the wear metals were signifigantly lower at the same mileage intervals as the Amsoil tests. I called and talked to both Mobil1 and Oil Analysis company's tech line, they both suggested that using a _W30 in the 4.6 can cause extra wear no matter the quality of the oil, since the engine is designed for thin oil with very tight tolerances. 5W20 for me forever!!

Verted

I wish that you hadn't analyzed the oil twice with Amsoil 0W30 in your GT! Then I would have figured that this was due to initial wear 'n tear. And analyzing it again after using 5W20 Mobil1, kinda drives the nail into the coffin. I could grasp at a straw and suggest that this was due to Mobil1 being superior to Amsoil (no matter what the viscosity), but that would be pushing it.

Thanks for clearing this up! Now I can feel good about changing my oil once again. I feel uncomfortable with ambiguity.

theedge67

Yeah, I believe Amsoil is very good oil, probably just as good if not better than Mobil1. I don't believe the problem was the oil quality at all, I believe it was the wrong viscosity. With so many very tight tolerances, the thin oil can get in there easier and quicker. just makes sense to me.

Also, it wasn't initial wear and tear, I put the Amsoil in at 10K miles, so break in metal was not a factor.

metroplex

Motorcraft 5W-20 until the warranty is over, then use whatever.
I run German Castrol 0W-30 in my 2003 Ford 5.4L 2V V8.

incomingRPG

Just used this trick this morning (Why didn't I think of that). THANK YOU!

metroplex

I used to use a plastic shopping bag to wrap my steering components (00 Crown Vic) but stopped doing it and just let the oil run over everything. It's cheap and easy rust proofing.

BTW I contacted Ford Australia and they use 5W-30 in the 5.4L 4V V8s in the Falcon XR8 (or as the Aussies call it, the Mustang Cabra engine).

incomingRPG

One problem with that is it ends up on the driveway or garage floor sooner or later if you don't wipe it off.

metroplex

My garage floor is thoroughly soaked with ATF already, so any engine oil driblets wouldn't matter too much

Mark S.

metroplex, doesn't the oil "down under" drain upwards instead of downwards?