I have seen a highway mode patch from a long time ago. First I cn't figure out how to use it and second I am not sure I need it with todays technoligy, mainly software like TunerPro.
Research shows the technoligy for hiway mode is in the 7747 but goverment said no because it ran outside of 14.7 to one AFR
My 2WD Suburban has a 7747 with overdrive trans and I think this would help MPG. Some of the research found articles written back in 2000 that told how it works but cooling pistons could be affected as it runs leaner so hotter and the cooling system just does not have the effect or capibilaty to cool pistons. This is the job of oil. Cooling system handles the cylinder walls. Point is this truck came with from the factory an oil cooler. Nice stacked plate one at that with hydralic fitting lines to adapter at oil cooler. But the transmission came with an old technoligy style finned over tubing type, so I guess GM knew of the technoligy back then but had to use up old stock finned over tubing coolers for the trans while oil got the new tecnoigy stacked plate cooler.
So point in my rant was oil has good cooler to help piston heat when using the hiway mode.
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