I have also noticed the amount of coolant in the tank from the expansion when the heat is on more with my 2.5 than with my turbo. No idea why, but this seems to match the experience of others on this forum. As an example, the distance from the full mark to the yellow line on @SilverOnyx’s turbo (post #12 above) is one-third the distance from the yellow mark on my 2.5, whose yellow mark is on top of overflow tank.
The expansion on my Ascent matches what @SilverOnyx reported, but the shape of the tank and the yellow marking on the Ascent are completely different. Although that yellow mark seems to match the hot level in the Outback, it’s nowhere near the hot level in the Ascent. I used to think that this yellow mark that started showing up on the 20 Outback specifically corresponded to the hot level, and that may be true, but since it’s so far into my Ascent, I’m starting to think that the whole this is a coincidence and is more of a quality control check that someone does on the production line, meaning they have verified the coolant level, no leaks, whatever.
I will add my mark to the reservoir on my Ascent so my tech knows how much to add to make up for the coolant that is disappearing. So far the Ascent’s coolant is disappearing at a much slower rate than the 2.5 in my 19 and 20 Outbacks. The turbo oil temp is consistently 10 degrees cooler than the 2.5, but the coolant temp gauge is at the same midpoint. If I had to guess, I’d guess the thermostat and resulting coolant temperature is the same for each engine, so the cooler oil temperature is a reflection of the turbo having to run less than the 2.5.
The turbo is definitely more eager as I rarely see more than 30mpg in drives I easily get 35-38 with the 2.5. Overall, I’m getting 25% less gas mileage with the turbo than with the 2.5, but that still puts me at the top of the range reported for both gas engines.
