Engine oil for Winter
Motul 8100 X-cess 5W-40 is a fully synthetic POE (grade 4) engine oil. I change this oil every 6,500-7,500 KM. Personally I be leave the oil change interval of 12,500 KM for a turbo charged Subaru is far to high. I use an engine oil with a 5W to help with the cold starts in the morning (4*C to 4*C). I’ve had good results with this engine oil and will continue to use it next winter. This fully synthetic engine oil with multiple manufacture approvals performs very well and I highly recommend it. I use an OEM Subaru oil filter.
Engine oil for Summer
Motul 8100 X-max 10W40 is a fully synthetic POE (grade 4) engine oil. I began using X-max to combat my thermal stress causing shearing issue I had when using X-cess during summer. With multi-grade SAE oils, the broader the SAE numbers the more viscosity improver needed. In a engine oil with a very broad multi-grade SAE such as 0W-40 or 5W-50, more viscosity improver is used. Viscosity improver (VI) is often the first component to degrade in fully synthetic oils, well before the base oil degrades. I use a 10W-40 SAE to to help with the hot summer days (28*C to 45*C with an average of 32*C). I change this oil every 8,000-9,000 KM. On paper this oil is very close to the specs of Shell Rotella 5W-40 full synthetic which has been raved about on most U.S Subaru forums but isn’t sold in Australia. I use an OEM Subaru oil filter.
Engine oil for Track Days
Motul 300V Chrono 10W-40 is a fully synthetic ester (grade 5) engine oil. This is a racing oil and should be used as such. I wouldn’t recommend using it for daily use as it lacks the amount of detergents normal engine oils would contain. Before a track day I would dump out the existing oil and fill it with 300V. I change this oil every 5,000 KM. The use of an ester base stock means the oil will be able to withstand high engine temps without shearing. I would recommend using a pink STI oil filter when using this oil.