In article , mike wrote:
On 26-03-2021 23:32 Ed Pawlowski wrote:

I care about making my car last.
Even a cheap car is a hefty investment

I follow the guidelines in the service manual that came with the car.

Following that book I've been driving my 1990 as my DD but since you're
worried I will tell you that for insurance against attacks by tigers
I've also carried an amethyst talisman in the trunk next to the manual.

No, you're not following the guidelines in the service manual. Because
if your car was made in 1990 then the oil described in the service manual
is no longer being manufactured.

Is the current oil better or worse than the oil that was originally
specified? It's likely much better. But you don't really know. All
you can do is drive and hope.

There are some cases in which the current oil formulations may be
problematic for older vehicles. 1990 isn't old enough to worry about,
but some people drive vehicles where they might worry.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."