Mixing oil weights

This is summer, you are putting in a heavier oil. You need to find another stop that has the 30 weight oil you require.

once you get that 30 weight, dig into your wallet and buy 5 more of what you always use an stick it into a side box against days like today.

 

I'd do it , and wouldn't have any trouble sleeping....

Go synthetic /$

 

I was told that mixing weights was always extraordinarily bad. Wal Mart carries Delvac 10/30, whole shelves of it. $16 & change per gallon.

 

Not everywhere they don't. Not here in Middle Tn.

 

I thought some engine manufacturers recommended heavier weight oil at higher ambient temperatures so what is the problem with that?
I do not like to mix weights or brands and would just use Delvac 15W-40 this time or second choice a different brand of 10W-30.
While driving an old truck on a gravel road once noticed the oil gauge was waving. Checked the dipstick for the second time that day, no oil. Found a black strip down the road from the hole in the oil filter and oh what luck an extra filter and some oil, 90 W. Got the filter off with my belt and a tie down winch bar or something. Still no oil on the stick but it had oil pressure. Stopped at the next little store and and filled it up with what ever they had even if it was recycled 30 W non detergent oil most of you don't remember. That truck ran for years afterwards. All that said just to say I disagree however Cat spd is probably correct.
Cat spd would you mind to explain your happy dollars and math justifying the extra expense of running true synthetic in a class 8 truck. Filter and oil change intervals? I don't mean that wrong it just did not pencil out for me years ago. It did for cars and I have seen impressive results if they were not changed over at high mileage.

 

T-6 changed at 18,000ish miles gives me a smile......


Does it give me the lowest figure on a spread sheet.....?

No, but when romping on that 600 plus hp in 90 degree air temps I have a smile on my face ...

 

Im going to offer a answer to that higher weights question.

Consider the 1971 351 Winsdor. The tolerances on that engine you can probably pass a few playing cards through the parts accessible by oil and due to it's top end characteristics you needed heavy oil in the summer, winter lighter.

Fast Forward to my Ex's 2006 engine. A V6 milled and machined with tolerances so small you cannot get but maybe 5 weight oil into it. Anything heavier threatens the entire engine.

That sir, is the extent of my personal theory on why you don't mix or go heavier than rated for a engine.

I usually changed oil on a big truck engine at 15K miles. Unfortunately some months that 15K happened twice a month triggering a DOT problem.

 

Thanks guys: I was just asking you to share your experience but is 15W 40 really out of spec for a DD16, none of those here.
I thank it's cowpie on the 10W 30 full syn program and some new Jap cars are running 0W 20 syn. I don't have to worry about 600+ HP and I still have pages in my log book from last year.

 

zero 20w?

Ya know, once the right material is reached in the correct places theoratically no oil? Big engines and small.