Straight weight oils

[meatshieldchris]

Does anyone run a straight 30 weight oil in their 2.9 in the summer? A friend suggested that it might offer more protection in the summer than a 5w30. Makes sense to me, as a 5w30 is a 5 weight oil that thins out like a 30 weight oil does when hot...I can imagine that a natural 30 weight instead of a modified 5 weight might be better except for cold startup.

 

[Big Jim M]

Truth?

Does anyone run a straight 30 weight oil in their 2.9 in the summer? A friend suggested that it might offer more protection in the summer than a 5w30. Makes sense to me, as a 5w30 is a 5 weight oil that thins out like a 30 weight oil does when hot...I can imagine that a natural 30 weight instead of a modified 5 weight might be better except for cold startup.

We don't know where you are. However, for the lower 48 using 30W in the summer won't make a bit of difference. In fact for most of the US 30W year around should work fine.
You got it a little backwards. 5W/30 oil get sthicker as it heats up...not getting thinner.. 5W is thin oil and 30W is much thicker.
Big JIm

 

[meatshieldchris]

We don't know where you are. However, for the lower 48 using 30W in the summer won't make a bit of difference. In fact for most of the US 30W year around should work fine.
You got it a little backwards. 5W/30 oil get sthicker as it heats up...not getting thinner.. 5W is thin oil and 30W is much thicker.
Big JIm

Central Canada. Summers swing from about 20C/68f to 35c/95f.

The multigrade oils have long chain molecules that curl up in a tight ball when cold, so you get the properties of the base oil, then extend when hot, faking a thicker base oil, not actually thickening up. 30w at 100c is thinner than 5w at 40c (check out any product spec sheet) It's not thickening up, it's thinning out less. http://www.calsci.com/motorcycleinfo/Oils1.html
But that's nit picking and too much reading.

I'm more wondering if there's something else that might be missing, for example, because of multi-grade's progression to a heavier behavior as it heats up, does it provide better protection than a straight weight if you're in a hotter than normal condition?

What about using a 10w30 instead? The oil doesn't have to compensate as much.

 

[Original_Ranger84]

You could run 10w30 in the summer if the temps stay like that. But swap back to 5w30 in the winter time. Too thick of oil in really cold weather will kill your motor and starting system.

But 5w30 provides all of the protection you need for the motor (people in texas and stuff run that and they have high mile engines) Running a straight 30w oil might help but it would not really make a difference.

 

[Spowerback]

I did half 5W30 / 10W30 which gives 7w30 and all going well. I think 5W30 is too low for motor

 

[exbass94]

We don't know where you are. However, for the lower 48 using 30W in the summer won't make a bit of difference. In fact for most of the US 30W year around should work fine.
You got it a little backwards. 5W/30 oil get sthicker as it heats up...not getting thinner.. 5W is thin oil and 30W is much thicker.
Big JIm

No, you have that all wrong. Oil does NOT thicken as it gets warmer, it gets thinner. The whole reason multi-viscosity oils were invented were because straight-weight oils thickened up too much in the winter. It's not an issue in warmer weather because oil gets THINNER when it's warmer.

The thing you need to understand is the first number (5w30) is NOT a viscosity number!!! A 5w30 is NOT a "5 weight" oil when cold. The first number simply refers to how viscous the oil becomes when cold. The higher the number, the more viscous it is.

This question actually just popped up on BITOG the other day. These guys can explain it much better than I can. I highly recommend you read it.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1929579&page=1

 

[Spowerback]

5w winter //// 10w summer
and the second number, heat index supports a given temperature, the more the better resist cipher is high at elevated heat

 

[Big Jim M]

Ok!

No, you have that all wrong. Oil does NOT thicken as it gets warmer, it gets thinner. The whole reason multi-viscosity oils were invented were because straight-weight oils thickened up too much in the winter. It's not an issue in warmer weather because oil gets THINNER when it's warmer.

The thing you need to understand is the first number (5w30) is NOT a viscosity number!!! A 5w30 is NOT a "5 weight" oil when cold. The first number simply refers to how viscous the oil becomes when cold. The higher the number, the more viscous it is.

This question actually just popped up on BITOG the other day. These guys can explain it much better than I can. I highly recommend you read it.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1929579&page=1

I read as much of that as I could stand.. Seems even the know-it-all guys on that site can't agree exactly about everything. The best post I read is:

"You are better off thinking that both act like a 30 weight at room temperature and above, the only difference being whether or not they can pass the 5w test which occurs at -25 degrees. At 40 and 100 degrees celcius, there is likely very little if any difference in the weight of either."

That seems to me to suit most of us better than the rest of the posts that I spent the time to read.
Big JIm

 

[chazzone]

90% of all engine wear occurs at start-up. The more viscous the oil, the longer it will take to protect the engine.

5W-30 will give better protection cold or hot than straight 30 wt.

-zz