A few weeks ago I was in despair. Black grot everywhere, a very sickly sounding Wreck indeed, and an alarming consumption of oil had left me convinced that the older of my two cars had a broken piston ring, something that is rather annoying to fix.
So I borrowed C's compression tester, a pressure gauge on a bit of pipe you screw into the hole where the spark plug goes, and measured the compression on all four cylinders. Perfect, all nearly the same, and all exactly where I expected them to be. This is an old engine, and it was designed with a low compression to run on the nastier grade of 1950s British petrol.
So the car hadn't destroyed a piston ring. Great. So what's up?
Back in the summer I overheated the car as its aged 1950s thermostat failed. Fortunately it's a tough engine so it can take it, but unfortunately it boiled its oil and a lot of it escaped in an impressive cloud of smoke. I had to buy a can of oil from a garage, and they didn't have the old-style 20w50 grade that used to be the mainstay lubricant for cars like the Wreck. I bought modern 10w40, a much thinner and more high-performance oil that wouldn't do the Wreck's engine any significant damage but definitely isn't the one recommended for it.
I think I've found out why 10w40 is not recommended for Wrecks. The thinner oil seeps past the aged rubber oil seals with ridiculous ease, which meant the cylinders were filling with oil from above rather than below as it flowed past the valve stem seals.
An engine flush that brought out an impressive amount of thick black gunk with the used oil, followed by new 20w50, a new filter and a can of oil seal rejuvenation additive, and I once again have a car that shows some semblance of reliability.
Why on earth do I run a car that does things like that to me? If you have to ask, you just don't understand. :)