Why 3,000 miles?

[GreeCguy]

Howdy again fellow oilers:
Digging through some old boxes out in the shop and found a Chilton's guide for GM Subcompact 1971-1980. Under the General information and maintenance section, said book says:
"Engine oil and filter should be changed every four months or 6,000 miles on all 1971-1974 models. On 1975 and later models, the interval is six months and 7,500 miles. Chevrolet bases these recommendations on the assumption that your cr is being used for average driving. Cerain types of driving requires that this interval not exceed three months of 3,000 miles. These include:
1. Operating the car under dusty conditions or during a dust storm. A dust storm may necessiate an immediate oil change.
2. Long periods of idling.
3. Trailer hauling.
4 Short tips at freezing temperatures when the engine hasn't had time to warm up sufficiently.
5. Comercial driving such as that performed by patrol cars, taxicabs, or limousines.
These recommended oil change intervals are based upon the assumption that a high quality SE oil is used; otherwise the intervals would have to be made shorter for the lower quality of oil."

Here's my question. This guide is made for cars built 25 to 30 years ago, and yet, we're talking 6,000 to 7,500 miles between changes. Oil today compared with oil then, (typical dino oil), is much, much better. Why then is everybody and their brother changing at 3,000 today? With me and all my SF rated oil, I should be able to easily go 5,000 miles per change with no problem as I don't qualify for any of the "severe conditions" listed above.
Is the 3,000 mile mark an extreme for the average day to day driver, (in the old fashioned sense of, "if one is good, two will be better)? Are we in fact wasting good oil that still has plenty of life left?

 

[ToyotaNSaturn]

quote:

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Originally posted by GreeCguy:
Are we in fact wasting good oil that still has plenty of life left?

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Mostly, yes. 3000 miles is really the least common marketing denominator for the public AND puts more $$ in the pockets of those who service vehicles.

Conversely, 3000 miles is too long of an interval for several engines, namely the Toyota and Dodge sludge-prone designs.

 

[TomH]

IMHO, the 3K mile OCI is nothing more than propaganda from the oil companies and quik lube places in order to boost their profit margins.

I'll admit that I was at one time a believer in the 3K mile OCI, but after reading info at good sites such as this, and my own personal experience, I now feel they are a waste of both money and oil with plenty of life left in it.

My OCIs are now anywhere between 5K and 6K miles.

 

[Tosh]

It also says "four months or 6000 miles." I would still say that is not as often as the other domestics of that era. Which brings up another point: Is this 71-74 GM subcompact actually a domestic car?
I suppose it's debatable which have progressed furthest since then: engines, oils, or air cleaners? I say thanks to electronics, engines have progressed the most.
As to the actual question: The car companies are just covering their own bum by specifying such frequent oil changes (for severe conditions). But they are getting better. And who would ever fault anyone for suggesting that it's better to be safe than sorry? Question is: Safe for whom?

 

[kenw]

""Question is: Safe for whom? "

the owner, that's who. period. Sure it covers the manufacturer, but only for the warranty period. After that they couldn't care less.

Given the choice of analyzing, worrying and making a hobby out of your car oil, normal Joes will err on the side of too-frequent and still drive their $30,000 or more vehicle for almost as long as they want. And have a pretty darn good, worry-free life. They have bigger things to worry about, like health, their kid's college and keeping a job.

No one in the world except a few BITOG members (and only a few mercifully) ever lost sleep over changing their oil TOO often.

Yes, it's a waste and it lines the pockets of those big bad oil change places.... Most people don't agonize over it. It's life: no one gets out alive.

Spend $500+/month in car payments, and a couple of extra oil changes over a year's time isn't something most normal people want to hassle with.

and no, 3k isn't too long for ANY engine, Toyota or otherwise.

 

[ediamiam]

5k makes a lot of sense as many of the posted uoa show tbn that would sustain 5k oci. on the other hand contemporary engines run a lot hotter and at higher rpms than engines of 30 years ago. fuel injection probably keeps fuel dilution more in check than engines that were carbureted. sludge prone engines is another kind of beast.

 

[Jimbo]

Higher rpms, yes, hotter, I dont think so. The crude forms of emission controls on carburated engines of the 1970s made engines run hotter than I see today. I base this on my own experiences and how many overheated cars I see on the side of the road this time of year vs two or more decades ago, a significant reduction.

Anyway, the combination of much better oil chemistry and modern fuel and ignition systems have made the 3000 mile OCI obsolete except for the smallest subset of cars driven very short distances in very cold weather.

My 1994 Chevy truck owners manual called for one year/7500mile intervals for light duty models under normal service and six months/6000miles for heavy duty models with gasoline engines. That is reasonable from my experiences with UOAs on conventional oils.