From: Mark A on
"SMS" <scharf.steven(a)> wrote in message
> There is no benefit in changing conventional oil every 3000 miles versus
> every 5000 miles, and the same holds true for synthetics.
> If you're doing extended oil change intervals, beyond the manufacturer's
> requirements, then you might extend the drain interval to at least the
> severe service interval.

Prove it.

From: SMS on
Mark A wrote:
> "SMS" <scharf.steven(a)> wrote in message
> news:3PzXk.8377$Ei5.1841(a)
>> I see. So what you're saying is that you have nothing to support your
>> recommendation.
> I have plenty to support it, and have posted it in other posts and other
> threads (many times).
> But I am not going to spend thousands of dollars to get "proof" of something
> that only costs $30 per year and whose benefits are largely intuitive to
> anyone with any brains.

That's your problem, you're unable to engage in critical thinking, so
you claim that it's "intuitive" even though you have absolutely nothing
to base that "intuition" on.

What you need to do is pay $16 for an oil analysis for both conventional
oil and synthetic oil. Then once you've seen that there's no difference
at 5000 miles, repeat it at 7500 miles and 10,000 miles. Here's one
source for oil analysis: "".

Of course you really don't have to spend this money, because the
manufacturers of synthetic oils have already done these tests, but they
don't want to publish the results for obvious reasons.

Now if you want to go 25,000 miles between oil changes, that changes
things, though you still would need to put in some additives between
changes to replace stuff like the acid neutralizers. That's one reason
why Mobil 1 backed down from their original advertising claims of very
high mileage intervals (another reason was because it violated the
manufacturer's requirements, and affected the ability of owners to
obtain warranty service).
From: SMS on
Ashton Crusher wrote:

> Unless you are servicing large diesel locomotives, and perhaps some
> large trucks, the only value to an oil analysis is to make money for
> the company providing the service or to help determine AFTER THE FACT
> what went wrong. For the cost of the analysis you could just have the
> oil changed.

Wrong. You get the analysis to determine the optimal change interval,
it's a one or time expense of less than $20, versus the continued cost
of changing your oil more often than necessary. You're thinking like
someone who decides that his old car will cost $1000 to fix, or he can
get new car for a down payment of $1000, so why fix the old car.

Of course you really don't need to do it yourself unless your driving
patterns are particularly different than average. It's already been done
for you by various agencies.


"The two-year study conducted by the State of California examined motor
oil longevity in a variety of vehicles, ranging from passenger cars to
large diesel engine busses. The 120 vehicles studied accumulated a
combined total of nearly 3 million miles. Laboratory analysis of the
motor oil tested during use lead to some surprising findings. For any
type of vehicle, oil change intervals can be simply and safely extended
beyond their current level to the maximum mileage recommended by the
vehicle/engine manufacturer."

From: Scott Dorsey on
Mark A <someone(a)> wrote:
>"Scott Dorsey" <kludge(a)> wrote in message
>> The thing is, the cost argument is a very good argument. I change my oil
>> every 3,000 miles, which works out to a little bit more often than once a
>> month. This adds up to a substantial cost in the end.
>Most people don't change their oil every 3000 miles, but let's look at your

This is bad. Because my sneaking suspicion is that in most cases (and
the case of the turbocharger is a good example of an exception) people
will benefit more per dollar with proper oil change intervals rather
than synthetic oil.

>If you used synthetic oil and changed every 5000 miles, I would guarantee
>you that your oil would be in better shape at 5000 miles with synthetic than
>at 3000 miles with conventional. So in your case, you would at least break

Depends on how much you're paying for the oil change (filter+labour) versus
the oil itself, but that could well be true.
"C'est un Nagra. C'est suisse, et tres, tres precis."
From: Scott Dorsey on
Mark A <someone(a)> wrote:
>"SMS" <scharf.steven(a)> wrote in message
>> <snip>
>>An oil analysis is a good investment to determine the optimum oil change
>> <snip>
>Can you prove that? I would like to seem a financial analysis of your claim.
>Don't forget to figure in the cost of a person's time, which in my case is
>about $60 per hour.

The problem is that one oil analysis tells you nothing... you have to keep
doing a whole bunch of them to get a good sense for what is going on.

With a big diesel engine that takes a lot of oil and uses an expensive
filter, oil analysis can save you a lot of money.

With a typical auto engine, reducing your oil change interval will cost
less than doing constant testing. However, if you are the sort of person
who wants to always know what is going on inside your engine and who might
want warning of possible failure with high mileage, it might be worth the
money to you. But that's more a psychological thing.
"C'est un Nagra. C'est suisse, et tres, tres precis."