[coop8070]

So I installed a vacuum Gauge in my 89 vw fox sedan 1.8 8v 4speed with cis-e mechanical fuel injection. When the car is fully warmed up and idling at 1k rpm the vacuum gauge shows 22 units (I don't know what vacuum is measured in). When driving I try to accelerate only letting the gauge drop to 10 at the lowest and my cruising goal is 20 but sometimes the car loses power to overcome a hill so my cruise will drop to 15 till I reach my desired speed.

Something funky is that in 4th gear the car can hit 20units at both 32mph/1500rpm and 45mph/2100rpm, of course the car is more capable of taking the hills at 45mph/2100rpm, and at the low rpm I have to drop the vacuum to 10 just to overcome the smallest inclines. My question is which speed is more fuel saving? Any tips you guys have as well?

27mpg before gauge and techniques, 30mpg after gauge, I need to hit 35mpg to make my daily commute cost $10 exact. There are a lot of unavoidable hills and stops in my commute as well.