Originally Posted By: Merkava_4
Is there anything that 10W-30 can do that 5W-30 can't do?
Yeah, it's typically a better oil that flows only a little bit slower in colder temps and 10W-30 also has other properties that are a little better IMO than 5w-30. Thus, if you don't need an oil that is "thin" at start-up due to many modern new engine's tighter tolerances that can impede oil flow, then you go with 10w-30. BTW, it's always very WISE to run what the manufacturer recommends for your engine. Why? Because they've put in a lot of time and money to research the best grade of oil that is applicable to your engine - that's why.
10W-30 CD (Diesel service grade) is predominately what we have been using in our entire fleet of engines where I work. There are approximately 30 internal combustion (gas and diesel) engines in our fleet. It's much more cost efficient to have only ONE grade of oil on hand, and it's a lot easier to prevent f-ups by mixing grades of oils unintentionally by workers that may add make-up oil here and there. Many people that are just worker-bee's don't necessarily know what they are doing, so trying to keep things as "idiot proof" as possible is a common theme where I work.
SAE 10W-30 is still pretty much hands-down the most universal oil you can use in our Upstate NY climate. We use it in small air-cooled engines, liquid-cooled engines, both gas and diesels. Works great, and have never had any major engine issues due to lubrication. Most all of our equipment is 20+ years old too.
Now, I have switched many of our more tired and larger diesels that don't run in the winter months much (or at all) over to SAE 15w-40 CD. Was it necessary? Well, probably not, but I did it due to personal preference, and to attempt to cut back on oil consumption a little bit between changes. I'd honestly prefer to run straight SAE 30 in some of them, but you never know when we're going to run those diesels in the winter months, and I don't want to risk any issues going that heavy in case it gets too cold out at any given time during the winter.
As for the higher temps, we change our engine oils often enough to where thermal breakdown and other issues with lighter oils don't much come into play. Truth be told, our climate is fairly moderate compared to many areas that get much colder in the winter, so I probably could run 30 wt in many of them and be just fine.
In case you wondered where I get my beliefs from, well... I'm a professional fleet maintenance and repair/fabrication mechanic that has been in this field for a very long time now, and as stated previously, I've never lost an engine due to lubrication issues.
One last note... And I'm NOT kidding about this at all. The vast majority of "quick-lube" places use bulk 10W-30 engine oil in EVERYTHING that comes through their door. Your car could call for something exotic, and guess what... it's getting 10W-30. For the most part, that's proof enough to show that 10w-30 is very "universal". HOWEVER, that reason alone is yet one of many other reasons that I always do my own oil changes and I never recommend any kind of "quick-lube" place to anyone.
