[petrolhead611]

Firstly I had better declare myself as the oldest established custom car cover maker in the UK(established January 1979). We do not however sell to the US or Canada as the insurance premium required to cover product liability for those two countries alone would actually double our annual business insurance costs, rendering such orders loss-making, so I have no axe to grind.. We have insurance to sell to the rest of the World, and we have shipped covers to every continent over the years( including North America because we can sell to Mexico).
Considerations for outdoor covers are as follows.
Is the fabric purpose made for car-covering purposes? Very few are, hence they do not breathe sufficiently(breathable garment fabrics are mostly useless for car covering as they depend on body heat for breathability)-a reputable cover-maker should be able to quote breathabilty figures, and incidentally also waterproof figures as well-if they can't, on what basis are they making their claims? A tailor-made cover using the right fabric shouldn't scratch the car-naturally provided that both the car and the non-scratch inner surface of the cover are grit-free when the cover is put on the car(this means the owner being careful to keep the cover clean and checking the paintwork prior to using the cover). UV degradation of many cheap fabrics is suprisingly rapid. A garage type cover( eg one that doesn't touch) the car should also be breathable to prevent condensation build-up(other than in arid environments of course)..
We won a UK car magazine's comparison test for outdoor covers wherein the fabric was subjected to proper lab tests for all the above performance considerations, whereas most magazine "tests" have just quoted from catalogues.