We have a 2011 Honda CR-V SE (AWD) that I was getting roughly 22mpg in city and up to 30mpg on highway until late last year. The car only has 57k miles and is in good shape, used mostly for short trips and limited mileage (have put only about 6k miles in 3 years since we bought it.)
At the end of last year, I had to get a new catalytic converter based on a check engine light. This was covered under EPA warranty by Honda Service.
Shortly after, I also had to replace my tires in order to pass the NY state inspection.
Since then, our mpg has dropped by about 50%. We get close to 12mpg in the city and about 20mpg on the highway.
I’ve taken it to Honda and they’ve said that this shouldn’t be the catalytic converter and the car is just getting old… Which is not a helpful response because clearly something is different The tires also have been inflated properly and the temperature change in NY hasn’t made any noticeable difference.
I’ve also seen from my Torque app and OBD scanner that there are some “incompletes” under Catalytic and O2, which leads me to believe there might be an issue with the emissions systems. (see attached pictures). We did have difficulty performing the drive cycle so that the new cat would pass the state test (had to drive 300+ miles).
Now this is starting to cost us a lot more for gas than we would like… It’ll probably be cheaper to just pay for the repairs, but we arent sure where to start as there are no codes and the car is otherwise running fine.
I was hoping the smart people of this forum may have some ideas to help us narrow it down before we have an expensive trial and error.
Some ideas from speaking to mechanics and doing research
Bad Catalytic converter or installation: an independent mechanic said it is possible that Honda used a bad part or did a shotty job because it was covered by the EPA warranty and that they could get me to come back and pay more. Don’t know about the conspiracy theory, but obviously around that time it stopped working.
O2 sensors: they did not replace these when changing the catalytic converter as far as I know. I’ve read that they should be swapped at the same time.
Spark plugs: mechanic mentioned this could be an issue, but also doesn’t seem like this should have that level of impact on mpg
Air filter: same as spark plugs
Wheel alignment: when we put new tires on, we did not have the wheels aligned. Probably should get this done soon but I don’t think this would cut Mpgs in half?
Drive cycle: the Honda service shop wasn’t able to so the recommended step by step drive cycle. Eventually after enough miles, the cat was operational and I passed the state test.
Thanks in advance. I appreciate any ideas or guidance you have here.
Yes, it could be a plugged up catalytic converter, but this thing is new and not likely. Other causes for bad gas mileage are:
Dirty fuel injectors
dirty air filter
spark plugs
an open and stuck thermostat never giving the engine an opportunity to get to operating temperature
Well, that was a stupid thing to say. “Old” in Honda parlance means more than 200,000 miles. 57k miles is still a baby.
Torque is great, but its one stumbling block is that it assumes you’re familiar with OBD scanning and therefore doesn’t really tell you what you need to know about what it displays. Heated catalyst is a non-continuously monitored sensor, which means unless conditions warrant the car looking at it, it’s going to return a “not avail,” but that doesn’t necessarily mean anything is wrong.
I don’t know the specific requirements for your car’s heated catalyst monitor to switch on, but usually it involves getting the engine up to temperature, then turning it off, back on, revving to a given RPM for a certain length of time (minutes, not seconds), then driving at a prescribed speed for another length of time, etc etc. If you haven’t followed the steps required, then you’ll get “not avail.”
You said you just got new tires… Really cheap ones? Tires not specified as low rolling resistance (LRR)? Tires have a large affect on fuel mileage, usually not THAT much, but large. What brand are they?
@kurtwm2010 has the rest of the list that are classic causes of poor mpg’s
I’d look into why the converter failed in the first place. The mechanic should have investigated that also. They generally last a lot longer than that. You may have another issue going on with the engine. Unburned fuel will burn up the converter. I doubt a new converter would affect gas mileage even if they used a cheap aftermarket one.
The Honda specific process is super involved (ie. Driving non stop at 50mph for 30+ mind) and hard to do in NYC unless you get up at 4am. Apparently I could pay Honda to do it for me but they didn’t think it was needed.
Would not completing a drive cycle properly cause fuel efficiency problems?
The tires are Bridgestone and definitely not the cheapest ones. The tread on the old tires was pretty warn which I imagine would have less resistance (and therefore better mpg)… But hard to imagine that dropping by half to your point
No, it would not. An incomplete simply means the computer does not have sufficient time, after the error codes were reset, to determine whether or not systems function properly. It may take several drive cycles to do that.
You must have been living in a different location before, unlikely that you could get 22 MPG driving short trips in New York City. You might get 15 to 17 MPG in big city traffic, perhaps recalculate your mileage.
To put things in perspective assuming 14 mpg overall vs 24 mpg overall the drop in mileage is costing you $210 per year at $3.50 mpg. Still want to spend a lot of money to fix it?
You have not told us how you determine your gas mileage, if your driving patterns have changed, does the engine still reach the same operating temp it did and lastly, are you sure no one is siphoning gas out of your tank.
When I was young and working at my first freight company there was someone there that started bragging about the gas mileage of his new car. It was tiring to listen to and the mileage he claimed was unlikely. We started adding 5 gal of gas to his tank every week. He grew ecstatic, His full size ford V8 was getting over 30 mpg around town. Then we stopped for a few weeks.
He stopped bragging and started asking where was a good place to get a tune up.
We then started siphoning 5 gal of gas out of his car until we removed all we had added.
Do it yourself when you fill up. Use the same pump and stop when the pump clicks off every time. Note your millage driven between fill-ups and divide by number of gallons put into the car (so for instance, if you drove 279 miles between fill ups and added 12 gallons of gas you would have a 23.25 mpg average). This will always give you the most accurate number (not saying the onboard calculator is wrong, they are usually pretty good, but this will give you the most definite answer for what your actual MPG is)
It is possible the calculator is having a brain fart, Glad the temp is good, I went from 18 to 16 on town, and 24 to 22 highway after switching from Michelin to bridgestone, next set of tires was michelin but gas mileage remains the same.
My car is not your car but asked mechanic bud to check out drop in mileage while in for fluid service and plugs etc, found a leaking fuel pressure regulator, it leaks into a vacuum hose, who knows where it goes, but no change in gas mileage after the fix.
I bought a new o2 sensor, have not put it in yet, but your mileage drop is significantly worse than mine.
In your shoes I would be concerned as it may lead to needing another Catalytic converter, try the old fashioned way of dividing miles by gallons for a few tanks, and see how hat works out.
If bad I would definately take it somewhere else for another opinion.
[quote=“kurtwm2010, post:2, topic:105416, full:true”]
Yes, it could be a plugged up catalytic converter, but this thing is new and not likely. Other causes for bad gas mileage are:
Dirty fuel injectors
dirty air filter
spark plugs
an open and stuck thermostat never giving the engine an opportunity to get to operating temperature
[/quote]A dirty air filter has almost no effect on fuel economy in a fuel injected vehicle.
A dirty air filter can reduce air flow, causing a too rich air-fuel mixture which can foul the spark plugs. The results can be diminished performance and increased gas consumption per mile.
[quote=“kurtwm2010, post:18, topic:105416, full:true”]
A dirty air filter can reduce air flow, causing a too rich air-fuel mixture which can foul the spark plugs. The results can be diminished performance and increased gas consumption per mile.
[/quote]It doesn’t work that way. The ECU compensates for the decreased airflow and keeps the mixture where it belongs. You will get reduced WOT power, though. But WOT is bad for fuel economy, so still no reduction in MPG.
The tires also have been inflated properly and the temperature change in NY hasn’t made any noticeable difference.
, but nothing would lead me to believe this is happening