What Are You Doing To/With Your Car Today?

Rechecked the calibration on my old Autometer 5" tach (I'd got it cheap because it read way off, and found that the glue on the cal pots had just dried out and come off. Reset with pulse generator and frequency counter).
But it's not perfectly linear - it reads 100 rpm low at 1000, 50 low at 2000, 100 low at 3000, right on at 4000 and 5000, about 100 high at 6000 and 7000, 150 high at 8000. Since I won't be revving over 7K no matter what, I guess that's close enough (100 of 3000 is only 3.3%)for a consumer-grade instrument subjected to automotive environment. Was hoping for 1% though.

Also went out for a short cruise (first day the % humidity hasn't been almost as high as the air temp!) with a smart phone propped on the dash, running a GPS speedometer app. Sure enough, 60 mph on the speedo is 57.5 on the GPS. Don't remember whether I put a 38 or 39 tooth gear in, but I need one more tooth ;)