1991 CQ with 7A with 310k miles loses 1 qt per 1000 miles.

[cgharibo]

Hi there,

My 1991 CQ with 7A engine appears to consume about 1 qt per 750 - 1000 miles. I barely used to add oil to this car. The car has 310,000 miles and I have used Mobil 1 15W50 every 7500 miles since new.

There is no white smoke, leaks, etc. The car pulls like it always has, you gotta rev it hard and I bring it to 4000-5000 rpm on a regular basis.

So, do I just keep adding oil and accept the increased oil consumption, change the oil weight, add an additive so it burns less oil.

What's the wisdom here?

Thank you!

[Tractor Dave]

Have you done a compression test?
Probably new rings and a bore hone and she will do another 310k

[K Simmonds]

At 310K miles I'd want to pull the sump and check the main and big end bearings, they're obviousy still okay otherwise it would sound rough but they are probably nearing the end of their life span. So as above a hone that removes about 1 thou and new set of rings 'should' sort out the oil consumption... However this very much depends on how the 310K miles have been accumulated, if that's from a lot of short journeys then the bores will very likely be oval requiring a rebore to the first oversize.

Regardless at 310K if I was to pull an engine appart to hone the bores I'd almost certainly end up replacing at least the main bearings whilst it's appart.

Changing oil weights won't make any real difference and don't be temted by any additives, they'll amost certainly do more harm than good.

Though that amount of oil consumpsion is just about acceptable so you could simply leave it alone and wait and see what happens.