15w-40 VS 10w-30

What is everybody's opinion on switching from 15 W 40 over to 10 W 30? I kinda don't feel very comfortable with it but I also don't know that much about it .. Just doesn't seem like it would provide the same protection??

I've also been reading up on it and seems like the 10 w30 might actually improve fuel mileage. I have an old 2005 C15 acert engine just don't know if it would run good I 10 W 30

 

Meh, not so sure I would use it on an older engine. Check the manufacturers approved oil list.
It’s main reason for use on modern engines is for fuel economy. But we are talking very small improvements. Like 1 or 2 percent.

 

Yeah seems like that really didn’t start until the SCR engines. I wouldn’t run it in anything non-SCR. A26 engine runs 10w-30 and it is normal for that engine to burn 1 quart in 1000 miles so I’m not convinced

 

Still using 15w40 in anything yellow. Rule of thumb is commonrail fuel systems 10w30 is Ok. Anything older should run 15w40. The amount of fuel saved from the switch will likely be barely noticable if at all.

 

Cats pushing 10W30... it’s all they have in bulk at my local cat house.

I use T6 and you get the best of both worlds....

 

I’d worry about causing a leak. I did that once using slick 50, yrs ago, bought a bunch on sale. Bad idea. Rear main started leaking, Luckily stopped after changing back. My Detroit has a front main leak now, due to thinning with diesel, after a bad injector. Never went away.I tried thinner synthetic on my car, only to blow most of it out. Now I throw in one quart of thicker oil, just to keep from adding between changes. It may be ok in cold, but summertime, I’d stick with 40w

 

All we have in bulk is 10w-30 too, but I don’t buy the hype. Maybe just splitting hairs though. When I worked at CAT dealer one of the old guys there told me. “It all comes out of the ground” because I couldn’t believe he was putting 15w-40 in his pick up truck.

 

They are using lighter oil for increase fuel economy, less internal drag from thicker oils. In my personal opinion, this is another attempt to increase sales of new trucks only and do not help with the overall longevity of the engine, just like the hype with extended intervals they push on buyers too.

 

If u wanna see a demonstration of what different oils do at different temperatures , adept ape has a video on youtube and he tests oil under different tempertures . its actually pretty cool

 

try not to stray too far off the manufacurers recommended oils.

they may have a "summer oil" blend and a "winter oil" blend, and if so, there is a reason for it...they tested it, and it's what works for thier engines.