I have run synthetic oil since 1977, I have never changed oil less than once per year. I have gone over 25,000 miles on the same synthetic oil and the engine never had a problem. In all these years I have only done 1 or 2 UOA and only out of curiosity.
Routine UOA is not cost effective for someone changing oil per the owners manual recommendations or less.
But on the other hand if you are going to do like me then it will pay off. In March I purchased a vg used 1992 one owner Chevy 4x4 pickup, short box with 305 and A/T. Loaded with all the options. Engine is vg at 75,000 miles now. I put in Amsoil XL7500 at 72,000 miles. It been in there for 3000 miles and the oil has not gone down at all. My plan is to install an Amsoil bypass oil filters, install the S2000 0W-30 and not change oil again till UOA says its time to change. I don't care about the miles or the time. I want to see how long the oil will go. I hope to get this done next week, truck is in shop this week having a new Western plow installed. This truck will be a work truck, plowing snow all winter, probably running as much as 6 hrs a day when needed and as my off-roader in other seasons. I have run the Amsoil 10W-40 for 5 yrs in my 1964 Impala because I did not rack up many miles and was only home occasional and had more important things to do. btw-I will only test the oil 1/year. If the body holds out, I plan to get at least 5 yrs work out of this truck.
[ September 11, 2003, 09:34 AM: Message edited by: Mike ]