Originally Posted by Katana29

Anyone had any experience with this?

I recently switched to running the 5w-40 T6 compared to the Mobil 1 10w-40 high mileage.

I found that it burns off significantly faster than the M1 (about a quart every 2500 miles). Valve train is also slightly nosier at highway speeds (I have aftermarket cams and the lifters tick until I get to operating temp). Normally they'd be silent but with this oil they are slightly more noticeable.

I looked up the flashpoints.

M1 10w-40 High Mileage- 239 C
T6 5w-40- 233 C
T6 15w-40- 249 C

I'm thinking the higher flashpoint will help resist burn off and partially explains what I'm seeing but I could be wrong. The motor is built with forged rods and pistons so the clearances are wider with more blow-by. I'm trying to find the best balance between oil consumption and lubrication. Temps never get above 180 with the oil cooler and the car holds an extra 1.5 quarts over stock.

I would have thought the thinner oil would have lubricated the upper parts of the engine more effectively but the slight increase in noise is leading me to believe a thicker oil is actually better for my case.

Any thoughts on this appreciated

Thanks
-James