I bought a bottle of Valvoline 10w30 conventional, a bottle of Valvoline 5w30 conventional, and a bottle of Delo 15w40. I put them in the refrigerator and got them down to about 42 deg. F. When shaking the two grades of Valvoline conventional, they were still relatively "watery". They both poured easily, with the 5w30 being just thinner enough to notice. Not much difference. The 15w40, though, was much thicker, feeling very different on the "shake test", and pouring noticeably slower.
Then I put them all in the freezer and got them down to about 0 deg. F. All were thicker, of course, but the Valvoline conventional grades still poured pretty well and passed the "shake test" as far as I was concerned. Still not a whole lot of difference between the Valvoline conventional grades, but enough to notice. The Delo 15w40, on the other hand, was thicker than molasses and didn't shake too well. Poured very slowly.
The purposes were to see if 10w30 would be a good year-round grade for southern California, and also to see the difference in an HD 15w40.
My conclusion is that in southern Cal., either 5w30 or 10w30 would be fine. I have an idea that in an engine that burns a little oil, the 10w30 might be better. If temps get very far below freezing, the 5w30 would pump a little faster. Secondly, in Valvoline conventional, there's not a great deal of difference in moderately low temp. performance between the 5w30 and 10w30. The 10w30, however, has a much lower NOACK number.
My other conclusion is that if I use HDEO, I'd rather use 10w30 under almost any conditions than 15w40. The exception would be constant Death Valley type heat. For summer use in LA or San Diego areas, I figure the 15w40 would probably be OK, but not my first choice unless I were doing a lot of towing or something like that.
Disclaimer: All of my vehicles have pretty high mileage and are out of warranty. If any were in warranty, I'd use whatever viscosity grade the warranty calls for. My vehicles all call for 5w30.
Then I put them all in the freezer and got them down to about 0 deg. F. All were thicker, of course, but the Valvoline conventional grades still poured pretty well and passed the "shake test" as far as I was concerned. Still not a whole lot of difference between the Valvoline conventional grades, but enough to notice. The Delo 15w40, on the other hand, was thicker than molasses and didn't shake too well. Poured very slowly.
The purposes were to see if 10w30 would be a good year-round grade for southern California, and also to see the difference in an HD 15w40.
My conclusion is that in southern Cal., either 5w30 or 10w30 would be fine. I have an idea that in an engine that burns a little oil, the 10w30 might be better. If temps get very far below freezing, the 5w30 would pump a little faster. Secondly, in Valvoline conventional, there's not a great deal of difference in moderately low temp. performance between the 5w30 and 10w30. The 10w30, however, has a much lower NOACK number.
My other conclusion is that if I use HDEO, I'd rather use 10w30 under almost any conditions than 15w40. The exception would be constant Death Valley type heat. For summer use in LA or San Diego areas, I figure the 15w40 would probably be OK, but not my first choice unless I were doing a lot of towing or something like that.
Disclaimer: All of my vehicles have pretty high mileage and are out of warranty. If any were in warranty, I'd use whatever viscosity grade the warranty calls for. My vehicles all call for 5w30.
