Hi. I put 94 legacy n/a into my  Vanagon a couple years ago. My first trip to Washington and then south to San Diego yielded mileage of 18-21 per gallon. I took a trip to Sacramento yesterday and got 12 . The  van ran strong and seemed to run as usual. I only noticed the fuel wasn't lasting too long. My wife drives the van mostly around town and is always filling up, I figure because of all the stop and go.

 My idle only seems a tad slow but it has always been that way. I pulled the plugs and did a comp check, 150-160. The plugs looked a bit lean but not like they get hot. 

 I can run at 70 all the way to Sac but generally keep around 60 - 65.

 The only oddity I see is my first water reserve goes low and doesn't push water into the overflow tank.

Just a wag but maybe the O2 sensor has failed and now the engine is running in that closed loop mode. 

 

 

Edit:  Forgot to also suggest the coolant temperature sensor.

Edited September 14, 201510 yr by john in KY

Would I not get a check engine light for either of these conditions? Is there a way to check the o2 sensor? 

 Thanks for reply. Appreciated.