<VV> Oil change

[Bill Elliott]

The breakdown in the long-chain polymers was indeed a problem in the 
past (and why the oil got "lighter" as it aged) but not so much today. I 
concur that in the old days, you'd see an oil pressure difference in 
that 3000-5000 mile range.

However, it's been interesting to look at the "oil change" indicators 
built into some of my "newer" cars (anybody that knows me knows I don't 
drive "new" cars...).

The wife's '89 BMW has an indicator, but I tend to believe it's based 
more on mileage than anything else (though I don't know for sure). It 
pretty regularly calls for a 5000-6000 mile change. The light must be 
manually reset.

In my '93 Allante, the oil change indicator was based on engine hours 
and load (reportedly)... interestingly, it indicated a need for an oil 
change more quickly with highway driving than it did with around town 
stop and go driving. But it never indicated an oil change in less than 
5000 miles... often as high as 7500 miles. It had to be manually reset.

The really strange one is my '98 BMW. It has NEVER shown the need for an 
oil change... despite that I change every 5000 miles and have never 
reset the light. I've put about 11,000 miles on the car since I bought 
it... I'm wondering if it is actually "reading" the oil somehow? Or it's 
just not working...

In my Corvairs, they get changed annually or 5000 miles, whichever comes 
first.

Bill

Padgett wrote:

> I used to have cars with very accurate oil pressure guages and my rule 
> of thumb was a 2-4 psi drop at cruising speed indicated it was time to 
> change the oil. Chevvies, FIATS, make did not matter and usually 
> occurred somewhere between 3,000 and 5,000 miles. Was once told by 
> someone who should have known that the cause was the breakdown in the 
> long chain polymers that made a multi-weight oil a multi-weight.
>
> Now that was some time ago but I still see the same thing happen.
>
> Keep in mind that European driving may be high speed but it is also 
> not for very long distances and, with few exceptions, on equivalents 
> to our two lane blacktops. They have also been making tiny engines for 
> a very long time and the cost of driving is much higher there than here.
>
> Padgett
>


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