Lost mileage with synthetic blend???

[HillbillyDeluxe39]

So wally world had Rotella 10w30 synthetic blend on sale for the same as regular 15w40, I figure winters coming so why not. 2000 miles later and Im noticing 3/4 to 1 mpg drop in mileage. Blow by and general oil consumption also seem to be a bit higher. 208,000 miles on motor its always drank oil since I bought it at 164,000 miles, about 1 quart every 2500 miles....

Anyone else run into this when going to synthetic or synthetic blend?

[MyTractorsSexy]

i run T6 full synthetic 5-40 or schaeffer 15-40 full synthetic i always stay with a thicker blend winter or not cause either way the engine still gets up to operating temps.

[ZMANN]

5-40 for me nice starts in winter

but no noticeable issues when going from Dino to syn

[HillbillyDeluxe39]

Yeah Im thinking the lighter weight is causing the excessive blow by and maybe to thin causing loss of mpg.

It doesnt really get that cold were Im at, so maybe Ill go back to regular, Is there a heavier weight than 15w40?

[blue99stroker]

there is 20w-50
but usually 5w-40 or 15w-40 is the norm

[LakiPolitis]

I'm a little unclear on my oil choice. I'm using Rotella 15w-40. I live in South Florida, so cold literally never happens. You guys think that's a good choice, or should I got with a heavier/lighter oil?