Gas mileage drop with no check engine light
Thread Starter
Joined: Jan 2020
Posts: 11
From: Anchorage, Alaska
After a good drive, walk around the car & see if any of the wheels are noticeable hotter than the others. But realize the fronts will be hotter because they do more braking work, and because of the engine heat. This is a better test if you already have a good idea of how hot they get "normally".
Another easy way to check is in a flat smooth parking lot. Get going slowly, about walking speed. Shift to neutral & coast, paying attention especially when it comes to a stop. Dragging brakes will make it lurch a bit right as it stops.
But the best way to check for dragging brakes is to lift each corner & spin the wheel.
There's other things that are less likely, so if neither the O2 sensor or the brakes are the culprit, come back for other things to check. It's a process of checking & ruling out each idea.
- tire pressure - you already checked.
- oil change - done; but does the engine use any oil between oil changes?
- engine developing more blowby, indicated by oil blowing back thru the vent into the air intake duct?
- clogged catalytic converter? (but I imagine you'd notice a loss of power)
I've often seen a dirty air filter as a suggestion but don't understand that. Unless it's an old carburated engine, a dirty air filter is equivalent to not opening the throttle as much. Probably good for MPG while limiting the max power.
Another easy way to check is in a flat smooth parking lot. Get going slowly, about walking speed. Shift to neutral & coast, paying attention especially when it comes to a stop. Dragging brakes will make it lurch a bit right as it stops.
But the best way to check for dragging brakes is to lift each corner & spin the wheel.
There's other things that are less likely, so if neither the O2 sensor or the brakes are the culprit, come back for other things to check. It's a process of checking & ruling out each idea.
- tire pressure - you already checked.
- oil change - done; but does the engine use any oil between oil changes?
- engine developing more blowby, indicated by oil blowing back thru the vent into the air intake duct?
- clogged catalytic converter? (but I imagine you'd notice a loss of power)
I've often seen a dirty air filter as a suggestion but don't understand that. Unless it's an old carburated engine, a dirty air filter is equivalent to not opening the throttle as much. Probably good for MPG while limiting the max power.
Thread Starter
Joined: Jan 2020
Posts: 11
From: Anchorage, Alaska
I will keep you posted! just changed the upstream sensor and topped off my gas tank. I’ll let you know in 300 miles or so if anything changed
Thread Starter
Joined: Jan 2020
Posts: 11
From: Anchorage, Alaska
and I got another question for you guys if you can answer this. My owners manual says the car takes 4.5 quarts of oil including the oil filter, and the past 3 times I’ve done oil changes it’s been taking 5+ quarts of oil to get it to the full level on the dipstick. I’ve parked it in my heated garage over night to let any oil settle to the bottom and I’m still getting low levels every time. Any clue?
Super Moderator
Joined: May 2006
Posts: 18,398
From: Wisconsin
I don't have specs in front of me for the K-series engine, but a dry-fill is always quite a bit more than the oil-change quantity. I think that's based on allowing a kinda short time for the oil to drain. There's a couple things that could cause more oil to drain out - therefore more oil needed to fill. In my case, I rotate the tires while the oil is draining, and that allows more oil to drain as I lift each corner to swap the wheels around. Another one I can think of is some oil filters have a larger can which can hold a little more oil. If you drain the oil cold, then it would take even longer to drain completely.
To make a long story short, trust the dipstick level rather than the number of quarts. (I guess you could look for a part number on the dipstick to see if it belongs to the wrong engine, but that's kinda bizarre)
To make a long story short, trust the dipstick level rather than the number of quarts. (I guess you could look for a part number on the dipstick to see if it belongs to the wrong engine, but that's kinda bizarre)
Thread Starter
Joined: Jan 2020
Posts: 11
From: Anchorage, Alaska
I don't have specs in front of me for the K-series engine, but a dry-fill is always quite a bit more than the oil-change quantity. I think that's based on allowing a kinda short time for the oil to drain. There's a couple things that could cause more oil to drain out - therefore more oil needed to fill. In my case, I rotate the tires while the oil is draining, and that allows more oil to drain as I lift each corner to swap the wheels around. Another one I can think of is some oil filters have a larger can which can hold a little more oil. If you drain the oil cold, then it would take even longer to drain completely.
To make a long story short, trust the dipstick level rather than the number of quarts. (I guess you could look for a part number on the dipstick to see if it belongs to the wrong engine, but that's kinda bizarre)
To make a long story short, trust the dipstick level rather than the number of quarts. (I guess you could look for a part number on the dipstick to see if it belongs to the wrong engine, but that's kinda bizarre)
Super Moderator
Joined: May 2006
Posts: 18,398
From: Wisconsin
Filters have to be the same where they screw onto the engine. But sometimes the metal can is longer, or wider, or something. I'm referring to comparing the dealer filter against all the other brands you can find. It's usually not enough to account for 1/2 quart but all that stuff adds up.
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