Hi,
I use my beloved Legacy just for "town" use and just a few highway ride each weekend; it is a second vehicule so I won't going to restor the engine.
since many mounthes I have air bubble in the coolant and there is for the moment a little quantity of CO² as the chemical test was not clear but not bad : the color was at a scale of 2 over a 5 levels scale so I suspect head gasket but maybe it would be a leak on the cabin heater pipes as I heard a lot of air bubble when I activate the heater and I get no warm.
But with 275000 km I'm aware the HG is not young but the oil level is stable and with no coolant so my problem is when I ride more than 45min there is too much air in the coolant and the engine temp is a little less cooled and a little more hot than an usual "good health " engine so I'm wondering if I should better use 10W-50 instead of 5W-40 as I use now ?
Thanks by advance