Wow that was scary went from straight 50 to 20W50 uh oh

[supersmitty]

I have been running valvoline 10w 40 in my 390 for 4 years now and the only issue I have is some blows out the valve cover vent but I change my oil every 2500 miles and I only have to add a half a quart between changes. I think it mostly happens when I am on the high for an extended period of time and the engine is staying at 3000 rpms.

[loveoftiki]

Mines the white 66 in the Poor Boys display downstairs, 100% original except for dropped beams, flipped axle, red and white pleated seat, Kustom 56 Buick Hubcaps. Got lots of plans for it, now just need the motivation to follow through. She's tons of fun the way she sits.

[Leeroy]

Have run 10w40 in both 351c slick and 289w mustang without any problem in either. Infact the reason I run multigrade was because both would make some lifter noise in the morning on a cold day if I ran straight 40 oil. Like others have said it sold depend on the engine, how old etc.

[Astrowing]

My 61 still has the paper on the glovebox door recommending 30w for 32-100f.