JosephJP
Member
With the A/C off my average mpg on my way to work is around 50. With A/C on it's around 40. Does this sound normal?
Average is the display read out for the trip. I haven't been able to do an actual calculation yet. I've only filled it up once so far.
I wouldn't agree that it's notoriously inaccurate. The MFD has actually always been spot on for me. I hand calculated each tank for a year and was always within 1-2 mpg from the MFD. In fact my mfd was a bit conservative.The numbers on the display are notoriously inaccurate, and checking within trips isn't a good way to make much of a definitive answer. It's like measuring a football field with a 6" ruler. You're going to be way off when you get to the other end..
Even averaging 20 tanks ambient conditions, traffic, wind, driving habits, etc will likely not net a good result for just testing the difference between the a/c on and off. Way too many variables and not many controls. The only reasonable way for you to get a decent delta would be to run a leg of a road multiple times with the a/c on, 1/2 tank worth and fill it up. Then do the same with the a/c off. Conditions will be as good as you can be and the vehicle will not have changed like it will in 12,000 miles [~20tanks].
Stays on unless the low pressure cutoff on the low side comes into play. Internal junk regulates the displacement of the compressor to maintain a constant pressure differential.How does the AC work on a MK4? When you select AC does the compressor stay engaged the entire time? Or does it cycle on and off?