We have had some heatwave here too, over +20C during day, today I did read +24C, but it did not really feel that warm at shadow at least.
Anyway my upper grille is blocked 75%, only 50% of upper grill intercooler hole is open.
Also at bottom grille 50% is blocked, that is lower part of it, no temp increase yet, so I'm thinking of adding bit more block to lower grille.
During winter I got some heat when I had everything blocked, but only at days where temp was near 0, still nothing too warm and now as I have front air dam, air will exit more freely from engine bay, so I don't need as much grille at open as I did before.
It seems to be really small amount of heat that diesel motor makes when getting over 60mpg.
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