I'm not afraid it'll be a bad engine, but it already only costs us one oil and one cobalt. Ultimately, and unfortunately, resource efficiency-wise this engine is as good as it's probably going to get. In game terms I can see adding a multi-stage compressor changing the engine costs by -1 Oil +1 Ore on a successful roll. Our "Draft" already costs 1 Oil - I don't see GM reducing it to 0 for us. Even if adding the Perc.-B to the Draught increased oil efficiency at the cost of that one ore, it's Expensive with our Oil and Ore costs within our threshold. A 1 Oil/1 Ore flip would put us over our ore limit, which would pop it over to VE, unless I'm mistaken on the rules (which I may be with the variety of ARs this forum has that I've been checking out). The Draft is also at our Ore threshold and considered Expensive already.
Now the engine will almost definitely increase performance, but right now numbers are our strength in the air. Cutting them down to 10% of what we have now is suicide, and something that
could happen with this revision.
Reading back through the resources thing in the OP, I did see something of note. Specifically, this in regards to Unique Resources:
As time goes on these resources may be discovered in areas on the map, or your side may find an exporter that they can purchase from.
As we do control vast swathes of possibly mineral-rich territory, what are thoughts on designing a Geological Survey Team at some point when we have some TC to utilize or shuffle around without ruining something?