I'm a chemist, but not an oil chemist, so this has me curious - why is it recommended to change oil every 3k miles OR 3 MONTHS? If it doesn't go bad over time, why not just every 3k miles, even if they are spread out over 10 years?

 

That is mostly intended to sell more oil. I've been changing the oil in my vehicles every 5K miles for 20 years and never had an engine failure. However, once the oil is in your motor and exposed to the combustion gasses, the additives do break down over time. Sitting in the can is completely different.

 

I think it's more because lots of short trips are harder on the oil than the same number of miles in long trips. 3 months of sitting still doesn't hurt the oil at all, but 3 months of city driving, totaling say 2,000 miles is something else altogether.

I put on about 1,200 - 1,500 miles a month, so when I was running natural (non-synthetic) oil I changed oil every 3,000 miles, even though I was spreading those miles between two different vehicles and it took 4 - 5 months for either one to hit 3,000.

By the way, back to the zinc additive, I've heard the reason for removing it was that it hurt the life of catalytic converters. Something that might be worth considering before running it in roller tappet engines.

 

something about condensation and chemical reactions with metals and creating an acid that eats away the metal.
but I'm no chemist, just an armchair internet jockey

 

I picked up a partial bottle of full synthetic SuperTech oil the other day that had been sitting on a shelf for probably a year. In the bottom it looked almost like mayonnaise had separated from the oil. According to what I've read from - Bob is the Oil Guy - Bob is the Oil Guy SuperTech is as good as any "regular" synthetic. This separation is making me wonder.....

 

Makes you wonder if you could mix it up and it would still be good oil to use or if its one of those things where its gone for good, kinda strange but it poses an interesting question.

 

That lower left pic is after I shook the hello out of it. It's going into the waste oil unless I decide to set it back and see what else happens to it.

 

Yes, that's why lots of short trips are hard on oil. The heat/cool cycles are where you get the condensation. An engine just sitting there for 3 months doesn't do that much (if at all). Oil just sitting in an engine doesn't go bad either.

 

We were not sure at first. Some of the older stuff is using ball bearing (less surface area) and the new stuff uses needle bearings. Plus the older stuff was made with a lower quality steel.

The Amsoil stuff is at 100-1. Seems spooky using oil that thin.

 

It is tough to run a prized piece of equipment at 50 or 70 to 1 at first. What sold me was the pro landscaping guys who go through gallons and gallons of two stroke mix every week. If they say it's OK that's enough for me.

 

Just got a new Stihl chain saw. They are doubling the warrantee if you buy a 6 pack of their synthetic at the time of purchase. They are calling for 50-1, but still seems weak. I guess if the manufacturer will tell you that.

 

Yup, it's the OIL, not the machine. That's why everyone gets confused.

 

I do agree with that way of thinking but everything I have read says it still isn't good for the oil once its in the engines because the block still does sweat so you still get condensation in the oil.
Personally in my vehicles that I only put a few hundred miles on over a course of a year. Not enough for an oil change per miles but overdue per "timeframe" And I still run them without changing the oil.

It isn't going to hurt it running 32-1 if you wanted, Just smoke a little more. Surely wouldn't void their warranty either I wouldn't think.
Cost you a little more in the extra oil used.
I don't run anything higher than a 40-1 regardless if they say it's ok.
Mainly because a mix of older and newer chainsaws so I just mix it at 32-1 for peace of mind. I run synthetic too so I'm probably pissing money away but it's better than a seized jug in my saws.
Its keeps the bugs away too sometimes

 

I used royal purple 100/1 (IIRC) in a CR500 I had, seized the motor on the first tank.