05-31-2009, 01:35 PM
Guys, with all due respect, given that the manual actually recommends a wide range of acceptable oil viscosities (and remember that the manual was written before synthetics became commonplace), and that any well-cared for engine can easily last upwards of 150K miles using any oil that falls anywhere within the recommended ranges, aren't statements like "I've always used [fill in the blank] weight oil, and haven't had any issues" a little silly? In other words, to really determine if the weight (and brand) of oil in any given engine is using is "good" or "bad", you'd have to either perform some sort of highly destructive accelerated wear test, or drive it at least 150K miles, tear it apart, and very carefully check all of the clearances. And you'd have to do this to several different engines, all using different weights (and brands?) of oil, making sure that each of the engines are driven as close to identically as possible over the term of the test.
In other words, you'd have to run a carefully controlled experiment over the course of many years, which is utterly impractical. This is why discussion of which is the "right" oil to use can get so passionate (check out www.bobistheoilguy.com to see what I mean) - because any claims, opinions, beliefs, etc., are virtually impossible to prove.
As long as you use a quality oil in the recommended range of viscosities, and change it and the filter at a reasonable interval (5-10K miles, depending on how you drive), you'll be fine. If you're trying to eek out the last horsepower or two in a racing application, then it's a different story, but for most typically-driven cars, sticking to a resonable regimen will reward you with a long engine life (unless a belt snaps - ouch!).
One last point - given the age of our engines, if you're really interested getting the maximum possible life out of your engine, I'd highly recommend doing an oil analysis. I had one done recently by Terrry Dyson (no affiliation), and was amazed at what I learned. My biggest issue is that too much unburnt is getting into my oil, compromising its effectiveness, so Terry recommended some correctivbe measures, the effectiveness of which I'll check with another analysis in 3000 miles. The analysis also showed that my air filter needed cleaning, there was some minor bearing wear (but not enough to warrant replacement yet - the fuel dilution is probably the culprit here), but that there is no water/antifreeze getting into my oil, and that the valvetrain, block, pistons, etc., are in very good shape. I wish I had done this when I got the car five years ago. Again, I would HIGHLY recommend anybody doing this - it could save you thousands of dollars in the long run. Plus, it provides actual data, rather than conjecture.
In other words, you'd have to run a carefully controlled experiment over the course of many years, which is utterly impractical. This is why discussion of which is the "right" oil to use can get so passionate (check out www.bobistheoilguy.com to see what I mean) - because any claims, opinions, beliefs, etc., are virtually impossible to prove.
As long as you use a quality oil in the recommended range of viscosities, and change it and the filter at a reasonable interval (5-10K miles, depending on how you drive), you'll be fine. If you're trying to eek out the last horsepower or two in a racing application, then it's a different story, but for most typically-driven cars, sticking to a resonable regimen will reward you with a long engine life (unless a belt snaps - ouch!).
One last point - given the age of our engines, if you're really interested getting the maximum possible life out of your engine, I'd highly recommend doing an oil analysis. I had one done recently by Terrry Dyson (no affiliation), and was amazed at what I learned. My biggest issue is that too much unburnt is getting into my oil, compromising its effectiveness, so Terry recommended some correctivbe measures, the effectiveness of which I'll check with another analysis in 3000 miles. The analysis also showed that my air filter needed cleaning, there was some minor bearing wear (but not enough to warrant replacement yet - the fuel dilution is probably the culprit here), but that there is no water/antifreeze getting into my oil, and that the valvetrain, block, pistons, etc., are in very good shape. I wish I had done this when I got the car five years ago. Again, I would HIGHLY recommend anybody doing this - it could save you thousands of dollars in the long run. Plus, it provides actual data, rather than conjecture.
This seems to be a set of conditions without a defined answer.