<VV> Fw: Multi-Grade 10W-40 Motor Oil in Corvairs ?

[Bill Elliott]

Back in the early days of multigrade oil, the viscosity modifiers which allowed the multigrade behavior would indeed be one of the first things that failed as the oil aged or was overheated. The wider the viscosity range, the worse the problem was. So for performance applications, a single viscosity afforded the best protection. 

However, all that is ancient history and the synthetic modifiers which all modern oils have (whether they are dino or synthetic) are extremely stable and now allows for extremely wide ranges.

Your cold engine wants a very low viscosity for the best cold lubrication... so I typically use 0W-40 or 5W-50 (fully synthetic) 

A discussion of oil selection by an expert Corvair owner: http://www.widman.biz/Corvair/html/oils.html

CC thread: http://corvaircenter.com/phorum/read.php?1,221690,page=1

Bill


"OK, 10W40 means 10 when cold, and 40 when hot, right ?  ("W" means "winter" 
? Why ?)

 Seems like they all prefer high viscosity in the 'cold' part and higher in 
the 'hot' part, but I've heard that multigrade oil breaks down faster (lose 
viscosity) when hot, which Corvairs do on occasion (most of the time, 
actually ?)

 So, single grade is still better ?  Recommended ? What ?"