Poor milage in 01 buick regal LS

[mat50ho]

I have no trouble codes stored or prestent. I have tuned up the car plugs, wires, fuel filer, kn air filter, new front oxyen sensor. Still the car only gets 23 on the highway.

I have a scan tool and all systems pass and no problems with temp sensors.



Matt Larson

[BNaylor]

Originally Posted by mat50ho

I have no trouble codes stored or prestent. I have tuned up the car plugs, wires, fuel filer, kn air filter, new front oxyen sensor. Still the car only gets 23 on the highway.

I have a scan tool and all systems pass and no problems with temp sensors.



Matt Larson

It might be helpful if you tell us the mileage on your Regal. The 23 mpg on the highway, is that without city driving like on a trip? How's your in city only? You're not that far off compared to my '99 Regal LS and '01 Regal GS.

On my Regal LS I get 20 - 21 in city only and 25 - 26 mpg strictly highway. Highway range is approx. 425 miles at 25 mpg. I could have sworn that it did better when I first got it back in 2000 but it has over 100K miles now.

[mat50ho]

57,000 miles on the car. If I have checked it quite a bit usually the will be 200 miles 180 higway 20 city. Not to much stop and go in the city. avg is 23 I have also checked it with just highway never seems to break into 24 mpg plus.

[BNaylor]

Originally Posted by mat50ho

57,000 miles on the car. If I have checked it quite a bit usually the will be 200 miles 180 higway 20 city. Not to much stop and go in the city. avg is 23 I have also checked it with just highway never seems to break into 24 mpg plus.

From what I can see its not that bad. In comparison I only get 18.5 mpg in city and 23 highway on my Regal GS. The LS does better but it doesn't have a supercharger either.

You mentioned earlier that you had the front 02 sensor replaced...was that with an OEM AC Delco? How about the rear 02 sensor and has the CAT convertor been checked. With higher mileage the CAT convertor loses efficiency but in your case not enough to give a P0420 DTC code since you have no SES light on, etc. However, the rear 02 sensor helps fine tune fuel injector pulse via the ECU/PCM computer but has to reference to the front 02 sensor to do so. It is active in ECU/PCM closed loop mode operation. IE: cruising, etc.

On my Regal LS at approx. 80K miles, I got a DTC error code of P0420 which is CAT operating below efficiency. The in city mileage dropped to 18 mpg. Replaced the CAT and rear 02 sensor together and the mileage went back to 20 - 21 in city. Of course I had to pay for CAT replacement because the GM emissions warranty on the CAT expired. Its 80K miles or 8 years, whichever comes first. Good luck!