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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?
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No gas leaks? Gas tank sizes are the same?
Also is there a chance the odometer on one of the cars is not accurate?
I test the speedometer and odometer by checking against those highway milemarkers you sometimes see on the side of the highway. For the speed, I just set cruise at 60 and it should take 60 seconds to make it one mile. Not a highly scientific test but close enough for GOVT work.Have you calculated their actual fuel economy? If the fuel tank holds more fuel on one car vs the other, then of course you’ll see a difference in miles per tank load. There were changes in these cars between those years. The google wizard says that the 2004 model gained up to 53 more pounds of curb weight and another 15HP over the 99 model. Maybe they gave up some tank volume to make room for 53 pounds of who knows what?
If you can prove there’s an actual difference in fuel economy mathematically, then it’s time to look at live PID’s on a scan tool. Fuel trims would be the first thing I’m looking at. Then adjust diag strategy based on what I read from the PID’s. You’ve got the benefit of comparing info between the cars too. I wouldn’t be against checking to make sure you don’t have brakes dragging either.
Yes, I’ve checked the odometer & its reading correctly. The math says my 2004 is getting 15.5mpg & the older car is getting about 24mpg. So a rather big difference.
It does seem to run higher rpms just slightly. I also notice a mild wrirling noise the 1999 doesn’t make. It seems to be tied to the throttle. I read a bad alternator can make the noise I hear, bit not sure the alternator would cut gas mileage by almost 10mpg. I have not checked the brakes, but wouldn’t they have noticed when they put the new tires on & balanced & aligned?
Oh, new air filter too
Ahm, you actually have nothing to complain about. It’s a gas guzzler.
http://www.fueleconomy.gov/feg/noframes/19710.shtml
See that City 16 mpg? I am also safely guessing, you do rather have a heavy right foot. Learn hypermiling techniques and you’ll see improvement.
Always remember – it’s not what you drive, it’s HOW you drive.Ya, NO. did u read the whole thread? I have the exact same car but older. The newer one gets 10mpg LESS than the exact same car 5 years older. Try again.
The 1999 gets 24mpg or about 340-370 miles per tank. The 2004 is getting 15.5 or about 240 miles per tank. All highway miles. Same specs. There’s no way my 2 cars would show a 10mpg discrepancy without something mechanical going on.
Looking for actual mechanical explanations. Not ignorant condescending suggestions. If it were that easy, I wouldn’t be posting here! Would I.
[quote=”rijnsburg” post=121125]I have not checked the brakes, but wouldn’t they have noticed when they put the new tires on & balanced & aligned?[/quote]
Not necessarily. As a mechanic myself, I might not look at the brakes if you don’t ask me to or if I don’t have time to check them out. A brake evaluation is still a billable service in some shops. In that scenario, I definitely wouldn’t look if I think there’s no way I’m going to make any money on it.
It may be a moot point for now anyway. This higher RPM that you’ve observed has my attention now. Is that higher RPM something you can observe more noticeably at idle? I don’t know what to think of how you described your sound so can you relate to it as more of a whine or a hiss? Maybe neither? Does the noise get better or worse with throttle?
My mind is trying to rationalize both symptoms being relative to a single problem like a vacuum leak. I’d really want to see those fuel trims at idle and then observe them again with the throttle opened. That would tell me whether or not I’m on the right track in diagnosing the car.
Tire shops are usually busy and are not gonna mess with inspecting other things.
Plus, are these two cars taken different routes like say the 99 sees mostly highway and the 04 mostly city, like if say someone you live with uses one car and you use the other?
One thing you could do is swap cars with whoever drives the other and see how gas mileage is effected.
Assuming the 04 runs pretty much perfect, there isn’t much that would cause serious MPG difference unless there is a gas leak somewhere.
I agree about the throttle situation. The noise is more of a whine the changes pitch up & down as you depress the gas & let it up. It “whines” constantly. It mildly sounds like a belt, only bec ause I the cyclical sound the whining makes. The 2004 idles at about the 1/2 mark (5000rpm), sometimes higher, where as the 1999 ifles very low, at around 250-300rpm. Ive tested on the highway….the 2004 is at 3000rpms by sbout 74mph, where as the 1999 has to get up to 83mph to hit 3000rpm. So at 80 mph, my older car is quiter. So im thinking this slightly higher idle is eating gas. I had read on this site awhile back, there was a video of someones whining engine that sounds exactly like mine. He changed the alternator in the video & the noise went away completely. Thats the only reason I thpught alternator on that, but im not convinced it would destroy my gas mileage that bad. Still wondering about this after market cat…it hasnt set the cel but he thinks it will. We did get one internal code on the CAT once, & he said when the 2nd internal code is tripped the cel will come on. He thought that should have happened already. I did just have a cel but I came up at a code for the thermostat because the 2 upstream o2 sensors were bad. Replaced both, no more cel, but it did not improve my mileage at all. So there’s something else going on. Vacuum leak is possible. ..I do have a tiny, almost unnoticable oil leak way down low, closer to ground level than top or middle of the block.
I am currently the only driver of both. I work from home, so the cars makes the same trips…out my rd, & in 2 minutes on the highway. Go 7 miles, get off & go about 1 miles on farm roads to drop my son at school. Hes getting his license in a few months which is why we bought the 2nd car. My son probably gets better gas mileage than me in both cars, but the 04 gets bad mileage regardless of who’s driving. That’s pretty much the only driving we do. The store is near his school, & I can walk to stuff in my town. I drive 25 min (about 30 miles each way) on the highway once a week to rehearsal, but that’s a straight road all the way, quite flat, & I set the cruise control & sail on down.
Actually, I’ll play it nice and apologize for unintended offense, taken so deeply.
For the sake of clrification, we do not know:
1. if one is 2WD and one is 4WD
2. is premium petrol used, as they are designed for premium 91
3. how is mpg calculated?
on personal note, there is no such thing as HWY drive ONLY. Does not exist. My drive is 75% HWY and every time I getting stuck in TRAFFIC it’s much worse than on the rest of the commute.
4. I have to insist, that mpg quoted (15.5) is actually not that far from real life mpg for 2004 RL. Some get it much worse, down to 13.http://acurazine.com/forums/second-generation-rl-2005-2012-76/tl-vs-rl-gas-mileage-497285/
And some folks there actually did improve their mpg – by changing driving habits and doing other improvements.
Fine, you need technical, 99% is highway miles. I live literally 1,000ft from the highway entrance. The school is one mile when we get off. Acura does not do a 4wd sedan smarty pants. Implying its normal & expected that my 2 same cars get a 10mile per gallon difference is ignorant. Or you really think I’m a moron! Either way, you are wrong!! If anything, the older car with more miles with some mechanical problems should NOT be getting 10mpg better. End of story. Its not the road, or driving habit, or gas, or the unicorn farm drinking the gas out of the car. If you dont have a MECHANICAL explanation, than you have no explanation.
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