Originally Posted by toner123

Well not like anyone asked for my opinion but here it is lol. First off I am in the Navy and I work on helicopters, MH-60S. I work in the Power Plants work center and pretty much my job is the maintaining of Turbo Shaft Engines, Rotor systems, and Gear Boxes. Now are engines both have a high and a low mark. To put it short if I CDI (inspector) a engine servicing to the high mark I am going to be in a world of sh$t. Now I can provide explaining on why we don't service it that high. As we all know when oil heats up it expands, well if there is to much oil in there you will have more expansion and no where for the oil to go. So if there is no where for the oil to go its going to start making its own room by pushing through seals, and working its way to the combustion section. Well I am no car guru but i can promise you that a car engine works the same exact way. The reason I would imagine Nissan has you service it that much is that it allows the room for expansion. The higher you put your oil on the dipstick from the recommended point is the less open room your oil has to expand. Now i promise you that if you start your car let it get to operating temp then shut it off and wait 15mins-1hr that your oil level is going to be way above that H mark if you are servicing it there, due to the expansion. Now service the car with the recommended oil amount and do the same thing it will be at the High point which is fine because the oil expanded and it is still in the safe range. So in other words I agree with Billarf, you want the oil to have room to expand or your going to ruin your engine. Oil is Oil regardless on what you use it on, basic characteristics apply. I am a person that does maintenance by the book, in my job if you don't then you kill someone The info i just gave is how we service a multi million dollar engine so we don't destroy it or kill someone due to it failing. What I say is it is your car do what ever the heck you want with it, run it in to a wall, drive it into a lake, go drive it with out any oil for all I car as long as no one gets hurt. I will service my oil to what Nissan says to service it to because I know what can happen with to much oil.

Frank