[serialk11r]

I took the car out with even more intake cam retard and saw a lower mpg number, and then I remembered that 101 on the Peninsula has a very very slight uphill grade to San Francisco (I usually get something like 2-5% more mpg going south vs north), so I did a bit of a longer test run in both directions. It seems I averaged about 26mpg going south and 24mpg going north, so I cannot definitively say if I've actually gained any mpg yet, as the higher air temperature today could easily have caused the difference, or differences in oil temp, etc.

However when I add in a few % more EGR, hopefully I get more mpg. I'm starting with 1.5-2% over stock, then I may add a little more if it looks like the EGR valve can support more flow. Assuming I have around 1.5 bar FMEP including throttle loss, I should see about a 1% increase in fuel economy from reduced pumping loss.

The biggest difference is definitely going to come from using lighter engine oil. I am still a little paranoid about dropping the viscosity too much, but I need to keep reminding myself that the factory recommended fill is Castrol which is comparatively thin (4.1cP for 5W50, 5.2cP for 10W60), and it's meant for a 10000 mile OCI. Using Mobil1 10w-40 at 3.9cP HTHS with an OCI of more like 4000 miles *should* be okay, if Castrol 5W-50 is fine.