BeerCan, my limited understanding of the situation is that Ford temporarily switched to metal pans on the F150's while they worked to resolve the issue. I believe the new F-150's are back to pastic.
Pew, you have a 1 L EcoBoost here in the States? Or did I misinterpret your statement? Which EcoBoost have you subjected to 170k miles? I'm very interested about your oil pan and drain plug combination and model year. Could you please share? Also, does your engine use direct injection? If so, has that presented any problems?
Skippy, yeah, the durability of the pan itself doesn't concern me. From what I've read, considerable testing was performed on these pans, and in many cases, they outperformed cast aluminum pans in several tests, including impact protection. It seems that they've been used on some commercial heavy duty vehicles since the late 90's. I think the polymer that is predominantly used is a glass-reinforced PA 6 (Nylon 6 (R)).
This is an article from 11 years ago:
https://www.plasticstoday.com/content/oil-pans-possible-new-pa6/65343831210655
This article has no date:
https://www.dsm.com/markets/enginee...lon/cases/akulon-ultraflow/oil-sump.html
My understanding with the Ford oil pans is that durability is not the issue. I believe one of the issues is with the plastic quarter-turn, o-ring style drain plug. I believe another is with the oil pan / engine block interface. Some have claimed that "warping" occurs in the composite pans. Perhaps, Aluminum and the plastic used in these pans have different coefficients of thermal expansion, which could stress the sealant used between the oil pan and the block. Then again, steel oil pans have been in use on aluminum engine blocks for decades. The ratio of the coefficient's of thermal expansion of Aluminum and Steel is about 2:1. For Nylon and Aluminum it's about 4:1 (
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html). It seems that the melting point of Nylon 6 is around 215 deg. C (
https://en.wikipedia.org/wiki/Nylon_6). Of course, perhaps the glass-reinforced formulation used in the oil pans has vastly different properties. In fact, the EngineeringToolbox site has an entry for the thermal expansion coefficient of glass-reinforced Nylon and it seems to be very similar to that of Aluminum, so the ratio would be roughly 1:1.
Of course, this is all just high-level analysis, using free online resources. I'd be very interested to hear from someone with a chemical background in plastics/polymers.