I've become a very outspoken fan of HDEO 15w-40's, so, of course, I am going to recommend you go for it!
First off, the converter issue is based off of the fact that HDEO's (Heavy Duty Engine Oil) contain a higher percentage of phorphorus. Now, while that is great in terms of anti-wear protection, it supposedly wreaks havoc on catalytic converters.
Well, that's not true. I've concluded this from my research: If you have a new car that requires the use of SL/GF-3 oil, then, yes, you will probably have reduced converter life (although still nothing I would worry about). If you have an older car, then you really have nothing to worry about unless your burning large amounts of oil.
The sulfated ash issue is also way overblow.
Simply put...the higher the amount of anti-wear and extreme pressure additives (which we all want in a lot of in our oils!)...the higher the sulfated ash level.
What people who say this is a big issue fail to realize is there are strict limits placed on the sulfated ash content in oils. While high amounts of AW/EP additives are good, they contribute to sulfated ash, which contributes to combustion chamber deposits and even top ring wear. The amount of sulfated ash in HDEO's is now around 1.3%...not enough to cause any problems. Truth be told, I bet that's why you now see molybdenum appearing in HDEO's...they need something else to add to give comparable protection to previous formulations that had higher levels of zinc/phorphorus and didn't have to deal with new regulations.
[ September 22, 2003, 01:37 PM: Message edited by: Jelly ]