Hello,

I have a 2005 S40 T5 with 137,000 plus and the gas mileage has decreased with every fill-up. After each fill-up, the mileage monitor says 425-450 to next fill-up, but of course I not getting nearly that many. I am currently get around 300 miles per fill-up using premium gas from Shell. I'm not sure this matter, but I read somewhere that possibly replacing the spark plugs and wires could improve the gas mileage. I appreciate any advice you guys might have. Thanks!

Cindi

 

the mileage monitor does a calculation based on average mpgs so once you start driving and your average mpgs chance, so will the miles to empty. So based on your actual miles and fill up gallons, what's your measured MPGs? If you drive mostly city, 20 MPG may be normal if you drive mostly highway, 27-28 would be in the normal range. If you don't have any check engine light issues, you may have a marginal fuel trim issue - vacuum line cracks, exhaust leaks, old plugs would be common causes. You don't have spark plug wires but the coil packs may need replacing - but usually they show as misfires (ie P030X OBD2 codes).

 

mt6127,

Thank you for the great information. I will definitely have those area checked.

 

You can also lose fuel mileage with tire air pressure too low. I tend to run mine a bit high at 40 psi cold. The recommended tire pressures on the door jamb are more for comfort. Normally the maximum hot tire pressure you ever want to see is 44 psi as listed on the sidewall of the tire.

 

Hindini,

Thank you for that information. I didn't think about checking my tires, but sure enough they were all uninflated....at around 28 psi. I've inflated them all at 40 psi since it's cold where I am now. Hope you have a wonderful day!!