[2016sierradi5.3]

I have 2016 sierra 5.3l with cylinder deactivation, I live in Ontario and during the summer months was able to achieve 11.5-12.3l/100km. On my daily commute I average 90km/h it runs about 1200rpm in 4cyl mode. There's two concerns first is now that the cooler temperatures are here I'm lucky to get 14.5l/100k , the truck runs colder and takes longer to heat up, I'm sure this is inheritent due to being direct injected and aluminum construction and the low rpms. It will not run 4cyl mode with the same load under colder temperatures. I can simply try to run a winter front to get to the under hood temps up but here's my second concern our awesome liberal government decided to invoke a carbon tax at the beginning of the year which has taxed our fuel about 4.5cents per litre. My thoughts were to run a mixtures of diesel with gasoline and eventually bio diesel. I've done a little reasearch and the idea seems plausible, with the direct injection my rail pressure is 1400psi similar to the older diesels, the engines compression ratio is 11:1 , I realize I do not own a diesel but hoping to improve fuel combustion characteristics and stored energy in the fuel. These are just some thoughts, I have considered an alcohol alternative but the temperatures in the winter are too cold to be reliable. What are some thoughts.