Pay no attention about the heat.
it means nothing.
There could be 140 degree air coming out the vents And it would feel pretty damn good.
But if the computer doesn’t go into the closed loop mode until the coolant reached 150-160 degrees, the computer will think the engine is still cold, and therefore use more gas.
Tester
ok thanks.
any comments regarding car makers saying NOT to use cleaners?
This would be more of a concern if the the car was under warranty, but there is little risk from using a reputable one.
There is no way an injector cleaner will fix a 1/3 drop in fuel economy.
Thanks NYBo.
I’ll consider everyone’s suggestions and go from there. If nothing works…i’ll be back!
I find it hard to believe the stoichiometric ratio (a.k.a. fuel/air) could go to hxxx in a hand basket without the CEL being triggered and leaving a herd of codes behind.
The odds (if even true) of this being related to fuel injectors or cured by a can is zero IMO.
You say you are sure of the mileage decline. So “sure” is based on what kind of testing? Unless it’s based on gallons needed to fill up vs miles driven then you are not sure. You are guessing.
Does the CEL light up when you turn the key, before you start the engine? Sellers have been known to disconnect them (unlikely, but easy to check).
Other causes could be parking brake partially on, damaged brake hose or sticky calipers causing brake drag. If you can get ahold of an infrared thermometer ($15) at Walmart, take the temperature of each rotor after a good drive. If there’s significant differences you may have brake problems
Check your tire pressures too. One or more could be low.
And go ahead and try the fuel injector cleaner. It can’t hurt anything.
If your mileage went from 300 down to 200, something is up. I would notice a 100 mile drop. You letting your kid borrow car?
Suit yourself but in the million plus miles I’ve never used an injector cleaner. The only injector problem I’ve ever had was at about 30,000 miles in my 86 Park Ave. The symptom though was intermittent extended cranking. It was caused by an injector sticking open and the shop had to resolve it with their injector cleaning treatment. And I’ve had up to 500,000 miles on original injectors with never having a bad one. The one time though I had excessive poor mileage, it was caused by an O2 sensor. I’m a consumer though, not a mechanic.
Over how many tankfulls have you noticed this dramatic change from 300mi to 200mi from a fillup?
When you’re approaching your car or when you’re stopped at a traffic light or when you shutoff the engine and get out of the car do you at any time smell or get a slight whiff of the odor of gasoline?
Have you moved recently from a warm climate to a colder area of the country?
When you’re filling the gas tank does the nozzle shutoff every 50 cents or dollar or so?
At idle does the engine labor occasionally like it’s going to die or otherwise hesitate when stepping on the gas?
When is the last time you changed the air filter?
Is it anyway possible that someone could be siphoning your tank?
One of the ways I’ve check for a stuck thermostat is if the radiator has a cap on it, when the engine is dead cold, remove the cap, start the engine and look into the radiator. If coolant is moving as if it’s circulating, the thermostat is stuck open and needs replacement.
While I agree with the rest of your reply, a dirty air filter has almost no effect on fuel economy in a modern fuel-injected vehicle.
Thanks for your response.
I agree and appreciate your point, a dirty air filter shouldn’t affect the fuel economy directly but it does indeed affect manifold pressure. Perhaps it’s not the 1/3 loss the OP claims. Without OBD readings, troubleshooting over the internet, right now, I’m shooting into a dark room.
Edward Michalowski