Yes the T4 diesel 15w40 oil is what i get, but i dont use it in everything, it is rathar thick for modern engines, i usually use it in older air cooled engines with some wear, the thicker oil helps in high heat environments. The T6 is the synthetic version a lot of my associates swear by it, i have never used it. For newer engines with few hrs on them i usually go with mobile ! or if its brand new, stick with the OEM oil for a while, only because it is specifically formulated for those engines and may help with the break in period. I know they say engines dont need to be broke in anymore, but i still baby them for a few hundred miles. Valvoline is another oil that many use that is available at Walmart Mart specifically for motorcycles and ATV, another i havent used but for many its there go to oil. I will try it at some point, the brand is one of the old reputable ones been around for a while and is good oil.