I just got a 2020 RDX Tech version and I noticed that on the information display that the Range (or Miles until Empty) isn't really changing. When I got the call the Range was 420 miles. After putting on 81 miles, it now reads 415 miles. It appears to think the gas tank is full. Anyone have this problem or how to reset it? Will another tank of gas fix it?

 

The estimate of miles to empty is based on your current gas consumption rate (i.e. miles per gallon in the US).

If you have been driving in the city for over 10 miles, then your average fuel economy may be 21 MPG, With a 17.1 gallon tank, you would have a range of 359 miles displayed.

As you drive out of the city and onto the highway, your average fuel economy would be 27 MPG after about 10 miles of highway driving. Assuming you drove a total of approximately 10 miles in the city and 10 miles on the highway, you would have consumed about 1 gallon of gas, which leaves 16.1 gallons still in the tank. Therefore your range is now 27MPG * 16.1gallons or 434 miles.

So you can see that after driving 10 miles in the city, and 10 miles on the highway, and consuming one gallon of gas, that your range actually increased by 79 miles.

So to answer your question, it is not unusual to see the range increase after driving for some time. It all depends on the type of road you are driving on.

To be more specific with your own numbers, if you had a full tank and an estimated range of 420 miles, then you were getting 24.6 MPG.
If you drove 41 miles at the 24.6 MPG rate, and 40 miles at the RDX's best rate of 27 MPG, you would have consumed 41/24.6 + 40/27 or 3.1 gallons of gas, which left 14 gallons in the tank.
If you had a range of 415 miles with 14 gallons available, then you decreased your MPG to 29 MPG.

I am willing to bet that your 81 miles was not put on 50/50 between city and highway, but a greater percentage was on the highway.

My experience with my 2020 RDX is that when the range is reported as zero, that it only takes about 15.6 gallons to fill up. This means that there is a safety factor of 1.5 gallons when the range says zero. When driving in the city this represents an additional 31 miles that can be driven.

Note: Since I am in Canada all of these values have been converted to US standards, to help the OP in understanding. I hope there are no errors.

 

Thank you for the explanation. It makes sense. Yes the first 30 minutes of owning the car was the car running with the salesman explaining to me all of the features. Then I drove about 70 miles mostly on the highway I couldn't find anyone mentioning this as a problem on the internet so I will give it more time to average out. .

 

If you select the Trip Computer on the MID you can see that the instantaneous gas consumption is constantly jumping up and down, while the average fuel economy changes very slowly over longer periods of time.

Your RANGE is based on the average fuel economy. You wouldn't want to see your RANGE jumping from 10 miles to 500 miles every-time you moved the accelerator.

So the RANGE value is actually based on the last 30 miles ( an educated guess). So when you first start driving on the highway, the RANGE is based on the last 30 miles of city driving (or low) . After 15 miles on the highway the RANGE is based on the average of your city and highway consumption' (i.e. your range may have started to go up). After 30 miles on the highway the RANGE is based on your best fuel economy and will reach it's highest value. After this point the RANGE will begin to slowly drop.

 

also, just my $0.02 which hopefully will help someone out there: to date, after owning the car for about 10 months, the most I have driven past the range showing 0 is 87 miles. Note that as the range approached zero for me typically i will baby the car more to see how far it will go and how far i am willing to test the limits of gas haha...

 

My fuel economy is better than I expected so I do not have any complaints there. I'm now at 25mpg, with about 70-80% highway.

I asked if the last 3 gallons in the tank are actually usable or it has 14 usable gallons in a 17.1 gallon tank. My low fuel lights triggers and says I have 25 miles of range when there are 3+ gallons left and I am getting 24.8-25.2mpg. I mentioned nothing about range in my question (which I don't care that much about) - I just want to know the usable size of the tank or if the range calculator is off by 50-75 miles. I'll ask when I take it in for the first oil change. It's not a huge deal in my case, but I really would like to know.

"We genuinely value you as an Acura client and we appreciate the opportunity of responding to your concern. On behalf of Acura, we are sorry to hear that you have concerns with the fuel range reading on your 2020 RDX. The skilled technicians at an Acura dealership are in the best position to evaluate your vehicle in order to determine the available corrective action. We rely on their Service Department to answer any technical questions regarding the vehicle, and diagnose any concerns. We encourage you to contact the Service Department of your preferred Acura dealership for assistance with diagnosis. If further assistance is required after visiting your Acura dealer, please do not hesitate to reach back out to us. Thank you and have a good rest of your day."

 

You are brave! I would need anti-anxiety meds to go 87 miles past 0.

Anyway, this may answer my question. It probably as 17 usable gallons and I'm filling up early for no reason. I'm taking it to 0 next time before I start looking for fuel.

 

I got an answer from the Acura rep and the service specialist: The are technically 17.1 usable gallons; however, the gauge is set to register 0 miles range remaining to protect the engine. If you run out of fuel in the DI engine apparently catastrophic engine failure can occur. So, it has 15 usable gallons with a sizable margin of safety built in.

 

Wow! I can only hope for the courage to get mine down into the single digit range to 0 when the weather warms up. Might have to tote around a 5 gallon gas can when I do try it...

 

Bumping this, as I was looking for an answer to same question - why does my fuel light come on so early and my range seem to zero out with (what should be) 2 gallons left in the tank? I love that I get more miles out of 15 gallons in this car than I did with 17 gallons in my 2010, but was still curious why filling up from "empty" would always be a hair over 15 gallons and not closer to the actual tank capacity (on my gen 1 RDX, if I filled up at 0 miles range I would get at least 17.5 gallons on an 18 gallon tank). Good to know it seems intentional by design, and that in a pinch I should have at least 50 miles left at 0 range, not that I have any plans to test it soon.

 

Manufacturers don't want you to run out of fuel so they make it so you have plenty of time to get to a gas station when the light comes on. They also don't want to be responsible for telling you that you have 15 miles left when you really only have 10 and are left stranded.

I don't like running my vehicles anywhere under 1/4 tank anyway. Old wives tale was that it was bad for the fuel pump. No clue if that's true, but I tend to err on the side of caution.

 

I've been driving Honda / Acura vehicles since the 80s and overall, I would say the low fuel light is set very very conservatively. Haven't really purposefully tested it but have had occasions where I have gone way past when the light has illuminated. We had an 09 4-cyl Accord and drove it 100% highway miles from VA to MA. The low fuel light came on just North of Hartford, CT and we continued to drive until almost home and was ~90 miles after after the light came on. Total trip was ~ 590 miles and only took 17.4 out of 18.5 gallons to fill the tank. I had an 04 TL and an 08 TL-S and easily drove 40 miles after the low fuel light came on both of them. My daughter has a 16 CR-V and has had one or two occasions where she has nervously needed to go beyond the low fuel light coming on, but had no issues. My wife has 16 RDX and I have a 2020 RDX and similar stories going beyond the low fuel light for a bit.
It's not a practice I would advocate for as I too have heard stories that running the fuel that low isn't good for the fuel pump or fuel filter, but if there is a need occasionally, it shouldn't be a big deal.

 

I remember seeing a video about a fuel pump failing on the new rdx's (with the 2.0 turbos). I had a 2023 RDX for 2 years and was always careful with how much time was spent while driving on low fuel because of that video. Fuel pumps are not cheap, and especially on these cars...my friend's RDX also suffered a failed fuel pump, so it leads me to believe these newer setups are more prone to failing.

My 07 TL is great though, I've run it with 0 km showing on the indicator many a time and no issues. I wouldn't risk the same with these newer cars though.

 

So, on that I do have some general info. In any modern set up, running the tank low, even very low, is not a cause for concern. The amount of gas that is needed to keep the in-tank pump cool and lubricated is miniscule compared to the volume of the tank itself. However, running it to completely dry (i.e. car sputters out because it's out of gas) can shorten the life of both the in tank pump as well as the high pressure fuel pump. Ideally there is some sensor that kills the high pressure pump when the in-tank one drops below a certain flow or pressure, but I'm not positive. That's where I'd err on the side of caution, but really any real modern car should have fail safes in place to prevent major component damage from running out of gas.

Basically, there is no harm in getting gas when the light comes on, or even at zero range on this car, since at that point you're still sitting on two whole gallons in the tank.

 

Consistently driving with a low fuel tank can harm a direct fuel injection system, according to AAA. They list these reasons

• Fuel Pump Overheating: The fuel pump relies on being submerged in gasoline for lubrication and cooling. When the fuel level is low, the pump has to work harder to draw in fuel and may not be fully submerged, leading to overheating and premature wear or failure.
• Debris Accumulation: Sediment and debris settle at the bottom of the fuel tank. Driving on low fuel increases the chances of these particles being sucked into the fuel system, potentially clogging the fuel filter and fuel injectors.
• Fuel Injector Clogging: If debris bypasses the fuel filter, it can clog or damage the fuel injectors, leading to poor engine performance, reduced power, and increased emissions.

To prevent these issues, it's recommended to refuel when your fuel tank is at least a quarter full.

 

AAA's advice is useful if you drive classic cars, and is probably as old as the average age of their members. That is not a danger on modern vehicles. But you're also not going to harm anything by following their advice.

To be clear, all of the above are causes for concern when you run extremely low, but will not happen at 1/4 tank or even 1/10 of a tank on the vast majority of cars on the road today.

 

I think I’ll err on the side of caution. This Acura dealer seems to think it a good idea not to go too low, and for mechanical reasons, not just running out of gas by the side of the road. Driving on an empty tank

Now he makes reference to a float as part of the fule pump assembly. Should you womnder what that ia about watch the video at

 

^^^I agree. As I mentioned above, I wouldn’t advocate for it, but once in a while likely isn’t an issue. I didn’t watch the video but my understanding is the pump relies on the gas for cooling. Running out of gas and burning out your fuel pump would be a real double kick in the ass.