[Srattani]

Hello,

i have 2019 honda accord touring cvt 1.5 and all of a sudden it is giving extremely poor mileage. I have only 47k km on it and i hardly drive it 5 km each day, i fill up the gas tank full and in roughly 1 week the tank is empty which used to last me for a month or more before . The trip computer shows on average 8 litres / 100 km in city which i think is quite normal but the tank is getting empty mechanic says until check engine light comes on it is like throwing darts trying to diagnose the issue, i came to this forum hoping someone has gone through similar issue and may know what might be wrong and help, thanks.

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Update. Problem seems to be getting worse, while stopped at red light completely for only 10 seconds or so as I was watching the "Trip Computer" the average fuel consumption went up from 12.7 liter/100km to 13.4 liter/100km. Also I noticed when I start up the car in the initial few seconds of driving the average fuel consumption is over 30 liter/100 km . I had to refuel again today

 

[Ash051]

Some 1.5T Accords experienced an oil dilution issue, where the oil was becoming contaminated with gasoline. So, are there any signs of the gas getting into the oil? You may be able to smell gas on the dipstick, the oil level may be unusually high, and it may be an abnormal color if this is the case.

If that checks out, you might have a leak somewhere.

 

[Srattani]

Some 1.5T Accords experienced an oil dilution issue, where the oil was becoming contaminated with gasoline. So, are there any signs of the gas getting into the oil? You may be able to smell gas on the dipstick, the oil level may be unusually high, and it may be an abnormal color if this is the case.

If that checks out, you might have a leak somewhere.

Thank you, if there is a leak wouldnt the CEL come on? I will ask him to check that

 

[easymike]

Thank you, if there is a leak wouldnt the CEL come on? I will ask him to check that

there wouldnt be a CEL from this. oil getting into the cylinders could eventually throw codes for misfires or emissions, but otherwise no. Follow @Ash051 s advice to rule that out or confirm.

 

[LARRY70GS]

How does it run? Any symptoms like lack of power? I'd ask your mechanic to scan the computer and look at the long and short term fuel trims.

 

[Hudouc]

Someone's stealing your gas?

 

[Srattani]

Someone's stealing your gas?

I am sure that’s not the case

 

[Srattani]

How does it run? Any symptoms like lack of power? I'd ask your mechanic to scan the computer and look at the long and short term fuel trims.

It runs normal, he did check and no codes

 

[Srattani]

there wouldnt be a CEL from this. oil getting into the cylinders could eventually throw codes for misfires or emissions, but otherwise no. Follow @Ash051 s advice to rule that out or confirm.

Will do, question, oil dilution causes poor mileage? I thought it causes engine problems and misfires and not mileage issues?

 

[Srattani]

Some 1.5T Accords experienced an oil dilution issue, where the oil was becoming contaminated with gasoline. So, are there any signs of the gas getting into the oil? You may be able to smell gas on the dipstick, the oil level may be unusually high, and it may be an abnormal color if this is the case.

If that checks out, you might have a leak somewhere.

Would oil dilution cause poor mileage? I thought that would cause engine misfires and problems no?

 

[Miker]

Are you determining the tank is full using only the gauge or when the pump clicks off during refueling? KPL would be OK but you have less fuel in the tank. Making you fill it up more often.

That make sense?

It is possible you have a backpressure problem in the tank vent that prevents filling the tank to the "top". I don't mean adding AFTER the nozzle clicks off on it's own.

If the nozzle clicks autonomously earlier than before, it LOOKS like it is filled but it isn't.

Regarding oil dilutiion problem, if the fuel is going into the oil I would suspect the fuel efficiency would suffer since that fuel is not being burnt. I'd also guess that if that IS the case you'd know if the oil was way over the level .

Very simple method you can check the dipstick of the oil and see if it reeks of fuel and the level is WAY over the full indicator.

 

[Ash051]

Would oil dilution cause poor mileage?

Yes.

If your gasoline is getting into the oil, it's not in the gas tank. Less gas in the gas tank means more frequent fill-ups.

 

[LARRY70GS]

It runs normal, he did check and no codes

No, that's not what I am talking about. A good scan tool, and I am sure your mechanic has one, reads out sensor values, and monitors various engine systems. One of the parameters is short and long term fuel trim. Fuel trim is basically the computers (PCM) adjustments to fuel injection. The PCM adds or subtracts fuel to keep it as close to perfect combustion as possible, 14.7 parts air to one part fuel. Normally, fuel trim numbers should be between 5 and 10%. Positive fuel trim numbers mean the PCM is adding fuel in response to a lean condition, and negative fuel trim numbers mean the PCM is removing fuel. Anything in excess of + or - 10% is abnormal. A bad mass air flow sensor won't set a code, but it might command more fuel because it is overestimating the air flow going past the throttle. The oxygen sensor would read the exhaust as rich, and the PCM will pull fuel.

Looking at the fuel trims, and Mass Air Flow sensor readings, as well as the oxygen sensor values should tell a story if the engine is using more fuel than it should.

If the fuel isn't leaking somewhere, than the engine is burning too much of it.

Your mechanic should know all of this. He should be able to diagnose the problem.

 

[Srattani]

Yes.

If your gasoline is getting into the oil, it's not in the gas tank. Less gas in the gas tank means more frequent fill-ups.

Thanks will definitely ask him to check, @Ash051 what is the fix for oil dilution, do you know?

 

[Srattani]

Are you determining the tank is full using only the gauge or when the pump clicks off during refueling? KPL would be OK but you have less fuel in the tank. Making you fill it up more often.

That make sense?

It is possible you have a backpressure problem in the tank vent that prevents filling the tank to the "top". I don't mean adding AFTER the nozzle clicks off on it's own.

If the nozzle clicks autonomously earlier than before, it LOOKS like it is filled but it isn't.

Regarding oil dilutiion problem, if the fuel is going into the oil I would suspect the fuel efficiency would suffer since that fuel is not being burnt. I'd also guess that if that IS the case you'd know if the oil was way over the level .

Very simple method you can check the dipstick of the oil and see if it reeks of fuel and the level is WAY over the full indicator.

I am always filling $60 worth of gas which is approx 35 or so litres so that is constant

 

[Srattani]

No, that's not what I am talking about. A good scan tool, and I am sure your mechanic has one, reads out sensor values, and monitors various engine systems. One of the parameters is short and long term fuel trim. Fuel trim is basically the computers (PCM) adjustments to fuel injection. The PCM adds or subtracts fuel to keep it as close to perfect combustion as possible, 14.7 parts air to one part fuel. Normally, fuel trim numbers should be between 5 and 10%. Positive fuel trim numbers mean the PCM is adding fuel in response to a lean condition, and negative fuel trim numbers mean the PCM is removing fuel. Anything in excess of + or - 10% is abnormal. A bad mass air flow sensor won't set a code, but it might command more fuel because it is overestimating the air flow going past the throttle. The oxygen sensor would read the exhaust as rich, and the PCM will pull fuel.

Looking at the fuel trims, and Mass Air Flow sensor readings, as well as the oxygen sensor values should tell a story if the engine is using more fuel than it should.

If the fuel isn't leaking somewhere, than the engine is burning too much of it.

Your mechanic should know all of this. He should be able to diagnose the problem.

I see I will ask him to check

 

[Srattani]

Update. Problem seems to be getting worse, while stopped at red light completely for only 10 seconds or so as I was watching the "Trip Computer" the average fuel consumption went up from 12.7 liter/100km to 13.4 liter/100km. Also I noticed when I start up the car in the initial few seconds of driving the average fuel consumption is over 30 liter/100 km . I had to refuel again today