Low mpg 2000 lesabre limited

[2000ltd]

I have 87k and just did a 195° thermostat and coolant flush. Car runs at 200°F and has new plugs, wires and coils. I've cleaned the MAF sensor with MAF sensor cleaner. Tires are at 38 psi. My dic computer says I get 30 mpg but I checked it at the pump and I get 20 mpg mostly highway miles. I think I may have an issue somewhere and I need help. I don't wanna parts cannon it if possible. Any ideas? All help is welcome.

 

[MelsRegal]

I have 87k and just did a 195° thermostat and coolant flush. Car runs at 200°F and has new plugs, wires and coils. I've cleaned the MAF sensor with MAF sensor cleaner. Tires are at 38 psi. My dic computer says I get 30 mpg but I checked it at the pump and I get 20 mpg mostly highway miles. I think I may have an issue somewhere and I need help. I don't wanna parts cannon it if possible. Any ideas? All help is welcome.

Explain how you checked it at the pump?

 

[2000ltd]

Explain how you checked it at the pump?

I filled up and drove 14 miles then filled up at same pump and checked pump. It said .689 gallons so I divided 14 by .689

 

[RD_Atlanta]

Try to expand expand your test. I prefer to fill the tank then drive until the tank is near empty then refill at the same pump and try to achieve the same fill level.

 

[2000ltd]

Try to expand expand your test. I prefer to fill the tank then drive until the tank is near empty then refill at the same pump and try to achieve the same fill level.

Ok I'll do that next time I fill up

 

[MelsRegal]

I filled up and drove 14 miles then filled up at same pump and checked pump. It said .689 gallons so I divided 14 by .689

I agree with prior comment, driving 14 miles is not a valid test. You have to use close to a tank full to obtain a valid number.