Some months back I brought a spare key for the breakaway switch, cleaning out the caravan boot, came across it, and decided to try it for fit, its the old "not quite the same size" trick! you'd think they could at least standardize on that!
I once carried a spare rotor around for ages, then early one morning I needed it, went to fit and it was the wrong bloody one, right number on box though.......
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Checking out the places I drove past a thousand times................
Unless a major job.
I always fit\install that new item. and keep the originals as the spare.
Then you know they both fit. and both work.
Especially Belts\Hoses etc. Even bearings. (and Dizzy caps yrs ago)
My opinion is.
I've usually got a few miles on them when I get spares. (Unless going on a long trip).
The originals have miles up but still fine.
New ones. You KNOW are good for usually X amount.
I'd rather run them till they go then install old ones
.
Knowing they still good to get me the (usually) short time\Dist to replacement point.
Than waiting for older. Worn items to go. in middle of nowhere usually
before installing the new ones that have been sitting there for sooo long doing nothing.
Just my way of doing things anyway
Says he that kept a 3 month supply of tinned\Dry foods on hes yacht all the time.
As a lot of us did in those days.