Originally Posted By: KCJeep
Interesting thread. The UOA link posted was interesting as well. Kind of makes you wonder about all the "flow at start up" and "wear at start up" theories doesn't it?
I'll have to pay more attention but I "think" some HD30's tend to be non detergent whereas most SAE30's mirror there multi-weight counterparts in add pack but are straight weights. Not sure on that I'll have to look harder next time I am in the oil aisle.
I do know I ran SAE30 without issue in our 87 Chevy years ago without apparent issue. I didn't know a thing about oil then but it had consumption with 5w30/10w30's. I tried the straight 30 in it and zero consumption. I didn't know anything about oil back then but now you've got me wondering what a summer run of straight 30 would look like UOA wise in my Jeep! Blasted BITOG anyway ha ha.
I have a 5 or 6 year old UOA from my trail Jeep that was very good running the Delo SAE30. If memory serves, I ran about 1500 street miles (back when it was still street legal) and many gallons of fuel burned off road. My Fe number was 9 PPM. Actually, I believe sodium was elevated in that UOA as well, but potassium was 0 and we determined it was the salt treated dirt roads we were using. The 2nd and 3rd UOA's confirmed.
There are many factors that contribute to start up wear. Acid build up, condensation, cold internal components, etc. If the oil is pump-able, then typically adequate lubrication is provided. Obviously this is only to a point if it's flippn' cold out.
Originally Posted By: turtlevette
Unless the oil is in its viscosity sweet spot its in its "plastic" state and does not lubricate as well.
Also, do you think oil in a syrup like state is going to sling properly to lubricate the piston and rings?
Hello?
Turtlevette's concerns do have validity. I have seen an old white paper where they tested multi-weights against straight cold start wear(5&10W30 vs SAE30) and the straight weight actually showed slightly less wear, but I can't remember the temperature of the test. I'm sure a modern test of a 5W30 vs a SAE30 consistently tested below freezing would show less wear with the multigrade. Whether or not the wear accounts to a decrease in the useful life of the engine is another matter.
In my personal use, I have used SAE30 below freezing and watched instant flow from the rockers (BuickGN did a similar "test" watching his Grand National with 20W50). I don't remember any weird noises and the UOA looked good (not that UOA's are a wear indicator, but we still use them as such). The issue I have noticed is the parasitic loss of having to pump SAE30 or even 10W40 vs the Grp III 5W30 oil I have settled on using in this vehicle. My last UOA was very good Fe wise, so why would I not take advantage of the better flow characteristics?