Hi All -
My shop used Valvoline (synth) 20w50 during my last fluid service a few weeks ago. After driving it 2,000 miles (not a typo) since the fluid service, I figured I better check to see if she had burned off a quart (or more). After a 30 minute drive, I checked the oil with the engine idling and I was very surprised to see the dipstick covered in coffee colored foam.
I normally use Redline (synth) 10w40 and the shop agreed to change the oil out to see if that cures the foaming.
What causes the oil to foam?
1) Over-filling with engine oil. Possible (nobody's perfect).
2) Condensation from disuse. Not possible in my case.
3) Contaminants in the system. Possible.
4) Wrong engine oil weight/viscosity for the conditions. Possible.
The first 3 I'm fairly certain of...it's #4 that I'm wondering about (hence the post). Could 20w50 be THAT different from 10w40 and cause foaming?
PS Temps and pressures throughout the 2,000 miles were spot on. Car drove normally and did not seem to be down on power. Fingers crossed it wasn't 'foaming' the entire drive but I have no way of knowing for sure.