extremely poor gas mileage!!!-no apparent cause

[Jules L.]

:blink:

So I have 2 of the same car. A 1999 & 2004 acura RL. The 1999 has 213,000 & the 2004 has 198,000

The 1999 gets ~375 gallons per tank, & although specs should be the same on the 2004, I only get 230 miles on the 2004. The 2004 has brand new tires & 4 wheel alignment & balancing. the 1999 has almost bald tires.

The 2004 has tons of new maintenance parts. New belts, new o2 sensors, new iridium plugs, new gas filter, just flushed coolant, oil changes with mobile 1 fully synthetic high mileage oil. It has a new CAT that was just installed prior to the car purchase a few months ago, but its after market, not oem. I have all service records & see nothing unusual prior to purchase.

So why the discrepancy between the two? What am I missing?

I have no check engine light. No codes. Runs amazing, powerful, shifts perfectly, quiet, smooth, no misfiring. Could the aftermarket cat be causing this? Or something else?

Topic

[Ingvar]

OP, just to add few Q-s:

– what’s the mileage difference between the vehicles? We naturally presume younger car has less miles on it, but it’s not always the case.
– – are YOU driving both vehicles, or one is for su esposa? Say, I alternate 2 completely different vehicles for commute, and have 2 different driving techniques, as one is hybrid. There may be difference between boy-drive and girl-drive styles too.

[Lorrin Barth]

I have to agree with ukrkoz, if EPA says 16 mpg in the city then that is the best you are going to get. Drive downhill from Denver on I-80 while everyone on the road passes you and you might break the EPA highway gas mileage.

The engineers who program the engine computer can decide to go lean for good mileage or rich to protect the engine. What they do in any particular year may be determined by the amount of pressure they receive from the marketing department, accounting, or the then current price of gas.

[Jules L.]

Sorry to step on all your male egos, but if you are one of the guys who are telling me 14 is normal, you are WRONG!!! CEL came on today…code for o2 sensors ( even tho they were replaced last week), a bad cat & bad thermostat!!!! The after market cat is a single bed converter, & my acura requires a dual bed converter. So o2 sensors are not getting up to temp because the single bed aftermarket cat is not designed for this car & thrpwing off the computer, resulting in a very rich mixture, which is eating all my gas.

Sorry guys! Obviously you guys never learned, NEVER question a woman’s intuition!!!

😀

[Jules L.]

& just so we’re clear, I am getting ~14 on the highway! I should be getting 24 on the highway. & I will again! Mark my words!

[Jules L.]

I am the only driver of both. The 1999 has 213,+++, & gets about 22-26mpg depending on time of year regardless of where I drive. It also has problems. … needed coil packs this year, fuel filter, air filter, plugs, it currently has bald tires, & needs a new fuel pump. Its misfiring & stalling but stil gets 10mpg better than the 2004 with 198,+++ miles.

Posted a minute ago the CEL came on today. Codes for o2 sensors even tho we just changed them last week, thermostat & catalytic converter, which I thought was the problem this whole time. Unfortunately, some people don’t Like to listen. They like to make assumptions before having all the info. Thank you for asking before assuming.

🙂

[James O’Hara]

O2 sensors won’t make a whirling sound and unless restricted neither would an exhaust. So while fixing the O2 sensors will probably help fuel economy greatly you may want to look at your pullies if one is going bad or bad it will restrict belt movement thus the engine has to increase rpms to get the belt to move the proper speed to move the belt driven devices. So if it turns out the o2 sensors don’t fix it all you might want to look into that.

[Author]

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