I do a 555 test. This is VERY important.
5 miles just to see if anyhing is not working. Thermostat,brakes,alternator,engine timing,trans/clutch,lights etc.
50 miles to see how the car runs at different speeds and if the brakes are getting hot. Put the car on the hoist and check everything looking for leaks. Test compression, head bolts, valve lash, fluid levels, tire pressure,etc.
500 mile test. Drive the car under different conditions, stop and go traffic, high speed, lower speed, panic stop, night driving (very important and usualy never done)driving in the rain ( maybe most important ) cold starts, hot starts, long idle periods. Look for leaks, check everything for tightness, add anifreeze ( only test drive with water) drain oil and change filter, adjust doors, hood, heaters and anything that might be needed.
In most cases you will find 90% of running problems in the first few miles. Most cars are driven around the block and called ready to go because the techs just don't have a whole day to spend on test driving.
On smaller jobs the test drive can be shorter. It has given me the oppertunity to drive some very nice cars over the years.
300SL, 220 Cab. A, 6.9, 6.3, 500SEC, 190SL's, 113's, 300b Conv., 220Seb Con., 6.3, 560SEC, 107's, 220S/220SE Cab., 170S Cab. A, 3.5 Coupe, 280SECab.,
123, 124, 126 and a number of other sedans and Coupes.
Daniel G Caron