Question:

So with my last fill-up, I noted an approximate 20% difference in my MPG fuel economy.

A bit of background.
  • I use this vehicle almost exclusively for commuting, like 98%. And that's a 40-mile commute that's almost entirely highway driving. And the route (except for the first appx 6 miles) is almost all straight & flat.
  • I drive at night, so I rarely use the AC and there's no heat-load on the vehicle or motor.
  • I've taken to setting my cruise to 60mph.
  • I've had tanks with an average of 54mpg for the last 3 fill-ups PRIOR to this one.
  • Now with the most recent tank, I've dropped to 46mpg.


I'm within just a few thousand miles of my end-of-warranty so...I'm obviously concerned if this is something I should be worried about taking care of.
But otherwise I've been fairly diligent about maintaining the vehicle, regular-cycle oil changes, actually...more often than the manufacturer recommends. As a former taxi driver I was diligent about changing that oil at the 5k mark.

Perhaps a simple plugs&wires tune-up?
What else am I looking at or for?

The vehicle doesn't seem to noticeably run or start rough.