Hi.I have a 2008 chevy 4.8L express cargo van with 110K.
I have noticed a gradual MPG decrease over the 3 weeks from 10.5MPG to 7.5MPG,driving about 30-40miles a day.
I 've put a new air-filter and new cables and sparkplugs. That helped me to get to 9.0 MPG .
I’m not sure ,what else could that be.
I’ve noticed that car may sound like it is running at higher RPM at any speed from 15-70mph and up , but i’m not 100% sure about it. That may be the only change ,but i’m only 20% sure about that noise. Transmission seems to work fine and car doesn’t lack acceleration and power.
Thank you for your help.