Oil change, ScanGauge...what the dilly, yo?

[theholycow]

Today I bring you my latest half-baked alarmist reaction to what is probably a mundane arithmetic error...

I brought the VW to the dealer for an oil change. They were doing the full synthetic (using VW-approved stuff) oil change for $30 as part of a promotion. That's less than I pay for oil and a filter.

I disconnected the ScanGauge when I got out of the car at the dealer and reconnected it before I drove away. I checked the odometer when I went in and out. Main odometer read 30127 and trip meter read 400. When I left, I'm sure the trip meter read ??0.1, and I think I would have noticed if it didn't read 40?.?. The invoice read 30127 for "Miles in" and "Miles out".

Today I got gas because the car was on E even though the ScanGauge said I had plenty of gas left. The ScanGauge said I went 550 miles and used 13 gallons. The gas pump and odometer said I went 582 miles and used 14 gallons. In this car the SG is always accurate for miles driven and close for fuel used.

Did the ScanGauge miss something, did it lose its calibration when I unplugged it (it never has before) (I'll have to check), or did the dealer drive 32 miles and I didn't notice? They did take forever and other customers were in and out while I waited.

I'll have to try to figure out how many miles I've put on since the oil change and see if there's 32 miles unaccounted for.

[Jay2TheRescue]

My SG always screws up when I disconnect it.

I have to go through the entire calibration and setup sequence. Its a pain, because I had to go through a lot to make the SG work reasonably well on the vehicle, (w/o the SG resetting the clock and radio presets). I never did figure out how to make it properly register DFCO though...

[trollbait]

While I didn't disconnect it, I'm in the middle of recalibrating my SG because of some screwiness. The trip mpg it reported was close as always to the cars DIC and calculated results, but when I set the fill up, it was reporting more gallons added to the tank than possible. Around double what I pumped in.