My wife started doing a 55 mile round trip commute again. It's been two years since she last did such a commute and although the highway is the same, city street destination is different.

Last fall I did the plugs/ Wires (Delphi brand)/ coils and the control module that sits under the coils. Ouch that control module isn't cheap.

She is complaining about gas mileage. The avg MPH is around 34 and the avg MPG is about 19. She seems to think the last time she commuted the MPG was better.

Car runs and idles smooth. Yesterday I installed a new air filter.

Two things:

In June 2008 my State started to require ethanol blend gas. Well you lose some MPG with the ethanol.

The second guess is that although the major highway is the same, she may be doing more traveling on the city streets. More traffic lights, stop signs etc.

No codes.

What say ye?

 

Is this a Concours - Northstar or Deville - 4.9 ?

 

Oops forgot that part.
It is a Concours with the Northstar engine

 

Your avg/avg mileage doesn't make any sense! I drive an 89 Concours 42 miles each way to/from work-80% 60-64 mph steady on Cruise. I get 22.5 to 23.5 mph-according to the display. If I drive it around town, 15-17 mpg is common.

chuck
98 Deville Concours

 

Make that a 98 Deville Concours!

chuck
98 Deville Concours

 

It appears with the low avg speed she is driving heavy or slow moving traffic alot. Volume of traffic or congestion skew mpg after all if your stuck idling for 5 min. while someone decides what their going to do that is 0 mpg @ 0 mph.

 

Looks like I am in the ball park for MPG. I thought the same thing but just wanted to validate my idea.

The car has about 120,000 on it. The previous owner, by the dealer was talked into a new engine. The PO heard a tic tic and the dealer said he needed a new engine. After many, many $thousands later, the car had a new engine. So there is now about 40,000 on the new engine.

This was my father in laws car and he gave it to my wife. I saw the work order and receipts for the new engine.

He was in CA and I was in PA. All we had to do was fly to CA and drive it home. He said that after getting the new engine another (non dealer) mechanic said he would not have needed a new engine.

The car does have a slight burp in the idle and you can feel it when your hands are on the wheel. But not always and I think it is more prevalent on a cold engine. I would guess at a possible coolant temp sensor but that should throw a code (not the thermostat temp sensor).

 

burp - at 120k plugs, wires, or corrosion on coil tower

 

Last fall I did the plugs/ Wires (Delphi brand)/ coils and the control module that sits under the coils.