I am with JK750 on this one bro. For instance, why do people say that the Golden rule is to change your engine oil in your car every 3k miles? They say that has been the traditional way back in the days. Granted, it would not hurt your car but I still need to know why this is practiced. Obviously, the TECHNOLOGY had advanced and as well as the formula so I was skeptical with that rule.
Fortunately, I was able to work in the R&D lab for engine oil. I found out that the 3k miles rule is not applicable but it's still encourage, it is MARKET oriented.
IMO, the <4yr rule is a good rule and I will encourage that as well since I have no Lab based background to support my cynical brain.
I am still curious though, where did that 4yr rule came from?
its actually law here in australia.... and it's because tyres harden over time, unless you store them in the perfect condition (which may include submersing them in a fluid), which will vary from tyre to tyre.
it's not a gimmic, and anyone on old tyres is an idiot, including me for not checking the tyre age on my gsx-r when i first bought it, and taking the guys word for them being 2 years old with 1000km on them, he was right about the 1000km bit, they looked brand new, and thats why i trusted him, but the 2 years was horseshit. they were 7 and 8 years old.
as for your oil comment, i disagree, at 3,000m/5,000km, most oils start breaking down, i know this from my own analysis and from working along side engine development teams at saab, bmw and suzuki.
the technology in oil has improved a lot over the years, but older oils actually held their detergency, lubrication and anti shear characteristics better due to the chemical compounds being legal, however the engine technology lacked.
engines now seal better, use cleaner fuels, and have better oiling systems then they did 30-40 years ago.
long life oils designed for euro cars, that is a different kettle of fish, those oils will go the distance, quite comfortably, but an earlier change is still better. the less crap in an engine the better it will run, i've pulled down motors i've maintained since new with 300,000km on them and not a single mark on any bearing, in scope wear, a linish and hone then reassemble.
in fact almost every customer who will allow me to service on my scheduling it ends up costing them about 15% less to run in the long term even with my servicing costs included.
oh and another thing, oil that is over 6 months old, will most likely be polluted, unless the vehicle is kept in a pretty good environment. (low humidity, stable temp, non ethanol based fuels used, allowed to warm up for a proper amount of time before being driven etc)