jw 1111 > wrote

> My car (toyota petrol 1.3) does a smallish mileage in a year say around
> 5000 miles, mainly on fairly short distances around town. what would be
> the 'time' limit
> to reasonably extend oil changes for economy reasons using a semi
> synthetic oil ?

Dont bother changing it.

> I suspect a lot of people will immediately say don't economize in this
> way.

Yep, plenty dont have a clue about the basics.

> However some forty years ago I had a conversation with a professor of an
> engineering college and he said engine oil does not degrade 'time wise'
> as fast as most people think ( and importantly as the oil companies would
> wish us to believe).

He's right.

> So by how much time could one reasonably delay an oil change with modern
> oils?

Once every decade is more than you need.