Rapeseed oil was used during the way to lubricate machinery since it could actually stick the wet metal. Pretty much the only country that was able to grow enough for the war was Canada who saw a huge boon as the crop swept the country. Eventually, the war ended and Canada was left with a bunch of terrible tasting oil that they spent millions on finding a way to make useable for cooking. Same general idea.

Same thing happened with Cottonseed oil. Worthless byproduct turned into "usable" product.

Also, yes, you can blame the fucking Leafs for poisoning the West by feeding them engine oil.