what is the difference between the two. I always run marine oil and a friend of mine uses regular oil from auto parts stores.his motor is a mercruzer 5.0 inboard outboard. he also runs a fram oil filter from auto parts as well he says it the same as a 305 smallblock chevy . 12,235. Location. Florida, Cape Coral. Oct 9, 2018. #8. There are some low grade 30 weights out in the market that arn't suitable for anything but the oil can. If a 30 is spected for diesel use then OK, otherwise use a stout 10w30 (T5) or a 15w40. JMO. B&S recommends a 5w30 Synthetic for ALL it's engines.Ed. No difference between 10w-40 and 15w-40 in terms of how well it will look after your engine except at startup. The 15w and the 10w just refers to how thick the oil is when cold. Once warmed up both oils are the same viscosity i.e. look after your engine just as well. Nissan specified 7.5w-30, so a 40 weight oil is better for a hard pressed AMSOIL 0W-30, 5W-30 and 10W-30 synthetic motor oils are ALL 30 weight oils. The answer is that ANY one can be used regardless of the vehicle owners manual recommendation. To better understand, in a 5W-30 oil, the "W" stands for winter performance. In winter weather the 0W oil will flow like a 0W oil, and the 5W will flow like a 5W oil and a 10W Hi. I still can't choose between those two oil weights. To stay with 10w-30 Or to move to 10w-40 at 280k. I been using both and noticed slight difference Using 10w-40 in increase of gas mileage, but better protection than 10w-30. Any comments,advices? Jun 27, 2016. #4. No worries - lots of Kubota's small diesels are used in tractors, skid steers, and stationary equipment. Kubota factory owner's manuals often list 10w-30 and 10w-40 as the recommended oil. The actual difference between these and 15w-40 is not perceptible to most owners. Shell has done a good job of promoting their Rotella 15w The Differences Between 10w40 & 15w50 Motorcycle Oil. 10w40 grade motorcycle oil will hold its performance right up to 40 degrees Celsius (104 degrees Fahrenheit), while the 15w50 grade motorcycle oil will hold its performance up to 50 degrees Celsius (122 degrees Fahrenheit). The number before the W tells you how the oil will flow in cold The 15w40 engine oil has excellent high thermal and oxidation stability. Temperature: The design temperature of 5w40 engine oil does not exceed 5 degrees. The lowest temperature you can expect from 15w-40 engine oil is 15 degrees. Price: The 5w40 oil price is around $48-$52. The 15w40 oil price is around$37-$42. The main difference between 10W-40 oil and 15W-40 oil is that 15W-40 oil has a higher viscosity than 10W-40 oil. 10W-40 oil allows the engine to run freely. Fellow Texans know if you regularly drive on I-35,80mph is the nominal average cruising speed if you don`t want to get run over. As per Z32 fsm,10W40-20W50 is recommended if the car is driven fast,raced,or in driven in hot climates,and 10W30 is recommended for fuel economy only. exx1jJD.