Oil change - fall or wait until spring?

[endless seas]

Fall,just knowing it is sitting for several months with clean oil opposed to dirty seams like the right thing to do...a happy engine makes a happy owner:smt001

 

[Boatingnut]

This would be a little more accurate discription of a multi-viscosity oil. What your describing is not how it works. Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

This is correct, and you beat me to it. Nice job and great info!

 

[gg51p]

I always do it in the spring. But I use mine year around.

 

[techmitch]

Hey guys, i could quote many a post here but let me say this, if you think for one second that marine grade oil is any thing like automotive oil take your car/suv or what ever out on the highway in 2nd or 3rd gear and run it at 3800+ rpms for a couple hrs. and then let me know how you make out.

 

[Jimmy Buoy]

Hey guys, i could quote many a post here but let me say this, if you think for one second that marine grade oil is any thing like automotive oil take your car/suv or what ever out on the highway in 2nd or 3rd gear and run it at 3800+ rpms for a couple hrs. and then let me know how you make out.

Right - but remember to also consider that you're strapping a fully loaded trailer to the hitch and then constantly going sharply uphill with that car/suv!:wow:

 

[Woody]

Hey guys, i could quote many a post here but let me say this, if you think for one second that marine grade oil is any thing like automotive oil take your car/suv or what ever out on the highway in 2nd or 3rd gear and run it at 3800+ rpms for a couple hrs. and then let me know how you make out.

Why would your test be the telling test? This test is done everyday in the real boating environment. There are numerous boaters out there that have followed the factory recommendations given them for their engines and those recommendations included automotive oils. We are not talking just “old” boats here but modern and recent engine designs. In fact Mercruiser still shows some SAE oils on their recommended list. I truly believe the most important contributor to engine longevity is not so much the oil choice but the oil change intervals and maintenance of all other systems on your engine. The lack of oil changes, filter maintenance…fuel, oil or air, improperly functioning fuel delivery systems, ignoring that little bit of sweetness you smell upon startup, etc will all affect the oil performance and engine longevity.

 

[BonBini]

Very interesting thread from a simple topic. Definatly change engine oil before lay up mostly due to the oils depleted ability to neutralize acids. Back when diesel fuel had sulfur in it, the sulfur and water made sulfuric acid and was really hard on lower end bearings. I don't know what gasoline puts down in the oil but it probably isn't good.

Running marine grade oil for the simple reason of lower operating temp is an interesting point made. 15/40 truck engine oil may not have the sheer strength for the rod bearings in a cooler running engine enviroment. I'm sure the oil temp will eventualy get up to where it needs to be, but getting up on plane:huh:. ...Ron