Forgive me father for I have sinned......by reviving an old oil thread.

But my inquiring mind wishes to know something.

I use Mobil 5w30 in my pickups and mustangs now....perfectly happy with it by the way.
Have considered the possibility of switching to Mobil 0w30.

So my questions are about stability and shearing.
Does an oil with a wider viscosity range break down quicker as some may suggest than one with a narrower viscosity range.

Example. Is 10w30 more stable than 5w30....and 5w30 more stable than 0w30 etc?

 

Just on a lube recipe question alone it's difficult to answer, because of the different base oils & additives available now days that can be used & to what specification the blender is trying to meet with that recipe & from the users standpoint, the engine type it's going to be used in, drive cycle, weather extremes, load, oci & fci that's being attempted.

So, if we choose a lube service grade & air, oil, fuel filtering grade other than specified, we should be backing those decisions up with some timely used oil analysis, to make sure we didn't overlook something when we choose to step out of the mfgr's equipment specifications.

Generally a 0W lube is for artic condition flow on cold starts, so if we live in warm country, we won't see as much benefit on our cold starts, as they aren't that extreme.

The 40C temp is just one point on a curve that our engines see for a very short time as they're warming up. It's the 100C operating temp viscosity & its stability over the oci we should be interested in & that will be affected by the lubricant & additive blending & use variables mentioned above, so it's not an easy thing to answer now days.

In the past when the blenders choices of base oil & additives were Much narrower in breadth & quality, it was thought that the narrower the viscosity spread, the more shear & oxidation stable the recipe would be. Now days 5W- & 10W-40 can be used in diesels, which heat, squeeze, shear & soot load the heck out of a lube!!!

SO, if we have an engine known to beat an oil up from those things, or is a sludger thats known to have poor oil circulation that stays in the top end too long & gets cooked & sheared such that it turns to sludge, we sure had better be choosing a quality lube & filter & changing them on time.
So choose your 0W lubes carefully & perform uoa's = Used Oil Analisis, to confirm its recipe is a good match for your engine, drive cycle & oci=Oil Change Interval.

 

Thanks for your reply ☺