Since new, I had run the Motul Transoil in the gearbox. Then, dumb me, ignoring all the good advice for what is the best for the x-mission, goes and tries Mobil 1 10W-40, and then a 0W-40 Mystic snowmobile/motorcycle gear oil and both of them made the x-mission notchy and really hard to find neut Compare Now. Shell Advance Ultra 4T 10W-40. Castrol Power1 Racing 10W40 4T. Compare Now. Motul 7100 10W40 100% Synthetic Engine Oil. Liqui Moly 10W-40 Full Synthetic Engine Oil - 1 Litre. Compare Now. Motul 7100 4T 20W50. Liqui Moly 20W-50 Full Synthetic Engine Oil - 1 Litre. In terms of density, the 20w50 is much denser than the 10w40 motor oil. 10w40 motor oil has a lower density of 865 kg/m3 than the denser 20w50 at 872 kg/m3. As for the mileage, there will be no increased mileage by using either 10w40 or 20w50. Additives A 10w40 motor oil has the viscosity of a ten-grade oil if cold and forty-grade oil if hot. A 20w40 motor oil can replace a 10w40 in the winter or cold weather or temperatures. However, a 10w40 motor oil can offer better lubrication and performance over a wide temperature range than the 20w40 motor oil. Feb 16, 2005. #4. Mobil 1 now has a 5w-40 called Truck & SUV oil. It is actually rebadged Delvac 1 used in heavy diesels . Since your car allows for it, this looks to be a good choice for your vehicle. If you want to use Mobil 1 10w-30, consider add a quart or two of the 15w-50 to thicken and beef up the additive package. The Valvoline 4 stroke got the attention of some customers as the best equivalent of the Honda gn4 10w40. Not only is it comfortable to utilize, but it is also cheap and affordable. This oil works and is good for four seasons of use as you follow the manufacturer's maintenance CE markings. The Valvoline 4 stroke is compatible with dirt bikes MOTUL 300V FACTORY LINE ROAD 10W-40 4T. Race bikes fitted with high performance 4 MOTUL 300V FACTORY LINE ROAD 15W-50 4T. Race bikes fitted with high performance 4 MOTUL 300V CHRONO 10W-40 AP. All racing Gasoline or diesel engines, MOTUL 300V HIGH RPM 0W-20 AP. 741 posts · Joined 2018. #31 · Apr 3, 2020. You guys overthink things. 10W-40 has been the common recommended oil weight in most vehicles for decades. Many decades. 10W-30 has been superceding it because the (slightly) lighter summer number is (slightly) better for fuel mileage. 0gxwc.