Daniel L

Porsche recommended 20k intervals for a while and they were rated up there with Toyota/Honda in reliability recently.

fishfryer

When I was a poor college student, 25 years ago, I used to change the filter in my 1979 5.0 Mustang every couple of thousand and just add a quart of Castrol GTX dino. Maybe every third time I'd drain the whole thing. That car went well over 200k miles without every having the valvecovers off. Oil and additives are so good and stable (especially synthetic) and bearings and metals are so well made, that that stuff holds up better than you can imagine. Motor failures come from bad manufacturing 'luck', not oil. Old motors fail now from cam wear due to low Zinc levels in most oils, but new motors on new oil almost NEVER fail. My guess is you can run a motor on dino oil for 50K miles and never change it and it would still run like new.

Think about a bike, it has clutch dust and crap in its oil and it needs to be changed every 3k and it revs to 16,000 RPM, the oil in a car has it easy. If a bike will run 100K on clutch polluted oil, a car is designed to probably almost NEVER have its oil changed.

JERO

I change our Odyssey's oil every 10K miles with M1 synthetic. Zero problems. And the oil life computer is crap. I went from 100% to 0% to 100% to 0% then 100% to 30% before changing it and the oil analysis was completely fine after 10K.

S2K is every 5K with top offs here and there.

Visit blackstone labs if your worried.

Saki GT

Actually you'd want a tribologist, which I believe RR is, and not a chemist.

Saki GT

[QUOTE=vader1,Jan 19 2011, 05:56 PM] He was, but my concern is not so much the break down of the properties of the oil, but the accumulation of gound up sand and dirt when the filter is toast.

dombey

I think this was partially a function of having large oil capacity?

Most owners I think changed earlier...habits die hard.

shyong

And what bike are you talking about? Are you saying a bike can run 100K miles on a single oil change interval? I don't think you have any idea what you're talking about. Just look up some search on google for oil analysis on bikes. Since both the motor and clutch uses the same oil, it degrades the oil all that much quicker. When you talk about thumper motors the oil change interval becomes all that much shorter.

Just go look up some sample analysis of oils and you'll be amazed at how oil quickly degrades in some cars/bikes. For you to say a "car is designed to probably almost NEVER have its oil changed"...it's a long stretch from the truth.

luder_5555

I have never done research on oil degradation, but I can say what I have noticed.

Car manufacturers have almost always recommended 3k mile intervals. There have been some slight differences between makes at times, but 3k became the standard. However now that many dealers are offering free maint on new cars, we are seeing this number double, and triple. I am not saying that if is necessary to change oil at 3k, or synth at 5k, but it does bother me that when they are the ones spending instead of making the money, the interval greatly increases.

I can also say that from years of working in shops, oil condition (how it looks coming out, not scientific I know) on some cars after 5k miles would be new looking while on others, it would be solid black even with regular 3k intervals.

I think that how you drive and whether or not your car is burning the oil has a lot to do with it.

On my miata I end up changing the oil about every 1-1.5k miles. This is mainly because I track the car a lot and do not run more than 2 track days on an oil change. Also I have noticed that before a track day the burn rate of the oil is very slow, but after a track day, it burns much faster. My guess for the excessive burning would be that it needs rings and valve seals, but I still think that how the car is used has as mch to do with it as anything.

Saki GT

When is the last time you "noticed"? The 3k mi interval started to disappear in the 90s, and the S2000 for example had a 7.5k mi interval since 1999. 5k-7.5k is the standard by all accounts I see today.

whiteflash

I just changed ran 10K on my oil, and it was just starting to get 'dirty'. I however offer no UOA, scientific experiments, or anything technical to justify this behavior.

Continue on as normal.