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I’ve heard some reports stating the turbo boast sucks gas like crazy. Anyone seeing poor gas mileage?
Yep, 20-21
But the engine isn’t broken in yet.
Turbos force air, the more air the more gas. The more air and gas, the more power. Plus, it has a high profile and AWD. I am not really expecting good gas mileage, even though I think it will improve out on the highway.
The stoichiometric mixture for a gasoline engine is the ideal ratio of air to fuel that burns all fuel with no excess air. For gasoline fuel, the stoichiometric air–fuel mixture is about 14.7:1 i.e. for every one gram of fuel, 14.7 grams of air are required.
I am right around 24 average, but anxious to see what I get when I drive all the way to Chicago on Wednesday from Kansas City. I am at 3400 miles total right now.
The highest I got was 25 going from Sacramento to Reno up over the mountains and back (man did this car handle great and climb great). I drive mostly city and am averaging about 19 to 20. I am also a bit of a lead foot.
Trip Computer (algorithm, based on internal measurement of fuel flow & distance): 24 mpg ave, 3279 miles (actual odometer reading today). My trip computer has not been reset since new.
Fuelly.com (calculated from actual miles travelled➗actual gallons used): 23.9 mpg ave, 3060 miles (tracked via Fuelly), 67/33% Hwy/City.
Lowest calculation by Fuelly to date has been 20.8 MPG; highest 27.4.
Note that my trip computer reading is very close to the calculation by Fuelly.com, which I have not experienced with past vehicles.
FYI if you are really obsessed with MPG — “Car and Driver” published an article on the discrepancy between MPG reported by a vehicle’s trip computer, and MPG calculated from gas pump and odometer readings. It stated: “To determine fuel efficiency, the [trip] computer keeps a running total of both the fuel delivered to the engine and the distance driven.” It goes on to explain why the computer-reported MPG can vary from reality. And, that Honda adds compensatory factors to its algorithm for computing MPG, trying to get it closer to reality. The article gives a method for equalizing fuel fill-ups at different gas pumps, which might be useful in getting closer to an accurate manual calculation.
“Why Your Trip Computer Isn’t Giving Accurate MPG Readings (And How to Fix It),” Aug 21, 2013. https://www.caranddriver.com/news/wh...-how-to-fix-it
I have an Advance awd which I drive in Comfort mode. Mainly been driving shorter trips no more than 15-20 miles. After ~1500 miles I'm at an average of 22.9mpg. I did however just take a trip from CT to PA and back which is a little over 300 miles one way with 95% interstate driving. On the way there I averaged 25.7mpg and on the way home 27.2mpg. Averaging 70-75 mph both ways.
I filled up today at Shell, and regular was $2.99 and the premium was $3.69.
I have not felt any lack of power, as I firmly believe that this is the Accord 2.0 engine which is rated for regular at a bit fewer horses and torque, while the RDX is rated for premium at a bit more horses and torque. It looks, to me, comparing curves, that premium gives about 10 lb-ft more torque at a100 higher RPMs, and can sustain that longer in the rev range, thereby boosting HP, due to the math. On a long drive, I will switch to premium and see how that goes.
I am in NYC. 90% city driving. Lights and stop-and -go traffic. MPG is pretty bad. 12-13mpg with auto stop feature off. Keeping it ON will save you 1-2mpg. My RDX 17' was better than that- 15-17MPG. 10-speed tranny does not do much in NYC driving.
Short answer: 20.8 mpg in spirited suburban driving in Sport mode. I have not done any long highway trips.
I've been looking at the trade-off of mileage, price, and octane. I miss the days when the spread was 10-20˘ per grade.
Anyway I'm finding that in suburban driving I gain 0.8 mpg going from 87 to 89 octane (20.0 mpg to 20.8), at a cost of 40˘/gal and gain another 1.0 mpg going from 87 to 93 at another 45-60˘ depending on the station. Around here few stations sell 91.
I can't say I really notice any difference in performance given the speeds I can normally drive. I don't have any roads here worthy of Sport+ mode... Few curves or hills in the Chicago area.
For now I'm pretty much just sticking to 89 unless I fill up at Costco where 93 doesn't carry such a higher price (and where it's a choice of only 87 or 93).
Just ending a three week camping trip, drove about 4,400 miles. Nine states, 8 National Parks. Average gas mileage was 25.5 mpg. Highest I ever get was 26.7. This was all in "Comfort" mode, using only Premium gas. All in all it was a great trip. Car was great, better gas milage then my old 2009 Honda CR-V. Which never got past 22 mpg.
I seem to be the exception here. Daily commute is 80 miles round trip with about 50 of those miles being on the interstate. The traffic is not bad for the drive, so not a lot of sitting still. In comfort mode, 93 octane and seeing 27.5 mpg the past few tanks. Trying to keep the speed under 75 on the current tank and looking to be above 28 MPG. I've noticed the car's MPG estimate is spot on to my hand calculation. The range number seems to hold back a gallon in its estimate.
Turbos force air, the more air the more gas. The more air and gas, the more power. Plus, it has a high profile and AWD. I am not really expecting good gas mileage, even though I think it will improve out on the highway.
from the wiki.
FYI when you have a turbo engine and are under moderate load (using the turbo) the computer adjusts the air to fuel ratio to 11:1 or so. Therefore you’re not only using more air=more gas, but using gas at a higher ratio per amount of air.
I filled up today at Shell, and regular was $2.99 and the premium was $3.69.
I have not felt any lack of power, as I firmly believe that this is the Accord 2.0 engine which is rated for regular at a bit fewer horses and torque, while the RDX is rated for premium at a bit more horses and torque. It looks, to me, comparing curves, that premium gives about 10 lb-ft more torque at a100 higher RPMs, and can sustain that longer in the rev range, thereby boosting HP, due to the math. On a long drive, I will switch to premium and see how that goes.
FYI
Turbo cars require premium 91 or higher octane because the gas is more stable, not because it makes more horsepower. In a turbocharged engine, the turbo creates boosted air pressure in the engines combustion chamber. Without the stability of higher octane gasoline, the fuel mixture often explodes because of the higher pressure before the spark can ignite it at the proper time. The result is knock or predetonation. It causes tiny nicks in your pistons and cylinder walks. Over time it can destroy the engine. Your vehicle has a “knock sensor” it works by detecting the knock and de powering the car through timing to reduce it. I’ve had a computer on a car to observe this phenomenon. When the knock is happening, it’s in the order of 30-60 knocks per second.
UPDATE: Last week, we drove from NJ to Stowe, Vermont and back. 80% highway with some spirited driving mixed in after the 600-mile recommended break-in period. 800 mile trip. 23.4 MPG on 93 Octane.
So far at just under 3,000 miles mixed urban, suburban and highway (~15%, 50%, 35%) I'm getting 24.2 using top tier (Shell, BP, Marathon, Sunoco) 87 octane.
So far at just under 3,000 miles mixed urban, suburban and highway (~15%, 50%, 35%) I'm getting 24.2 using top tier (Shell, BP, Marathon, Sunoco) 87 octane.
FYI
Turbo cars require premium 91 or higher octane because the gas is more stable, not because it makes more horsepower. In a turbocharged engine, the turbo creates boosted air pressure in the engines combustion chamber. Without the stability of higher octane gasoline, the fuel mixture often explodes because of the higher pressure before the spark can ignite it at the proper time. The result is knock or predetonation. It causes tiny nicks in your pistons and cylinder walks. Over time it can destroy the engine. Your vehicle has a “knock sensor” it works by detecting the knock and de powering the car through timing to reduce it. I’ve had a computer on a car to observe this phenomenon. When the knock is happening, it’s in the order of 30-60 knocks per second.
The manufacturer, Honda, says the Honda 2.0 requires 87. Acura recommends 91, but a simple look at the fuel filler shows that it requires 87.
Some turbo engines require premium, for some it is only recommended, and for others, it is not even recommended by the manufacturer.
20-23 mpg here (A-spec FWD) on 91 gas with auto-engine-off enabled, 50/50 split of highway/city. Currently testing if idle engine off makes a difference. I spend a lot of time stuck in traffic
After reaching 2,000 miles, our mileage has gotten better. We're averaging 24.3 mpg with 60 city/40 hwy (Advance FWD, premium gas, Auto Idle Off disengaged).
Just got back from a 280 mile round trip. Rolling topography with a couple of 600 foot hills, about 25/75 city/highway, highway speed was 55-80 with the majority around 70-75. Mileage for the trip was 25.3, BP 87 octane.
As I planned, I switched over to 93 at 3000 miles. It looks like I picked up just short of 10% better mileage for a bit more than 15% extra cost. I am not feeling more power on my butt dyno, but the engine feels and sounds like it runs smoother. I will keep using top tier 93 for the next 3K miles, then make a decision.
I posted this chart elsewhere (on the “other” mpg thread) but can’t hurt to add it to this one. Explanatory note is in the image; my own results to-date are part of my signature. On Fuelly’s chart, my RDX is one of the three that are averaging 25 mpg.
FWIW, I mostly use Costco’s 93 octane “top tier” product. On the road I use mostly BP mid-grade (89 oct), because I’m cheap—I prefer their quality gas over other brands, but BP charges as much as $.50 more per gallon for 89 than my Costco charges for 93; BP’s 93 is almost $1 more than Costco’s (at least, it is at stations I’ve used near interchanges on I-85 and I-95).
I’d like to find a reliable source for some good-quality, ethanol-free gas (intended for road use) to try over several fill-ups, but it is fairly difficult to find. I stumbled on some last month at a WaWa in FL, but haven’t found it elsewhere on the road. WaWa’s website says they plan to expand availability nationwide, but it is happening at a slow pace.
From fuellly.com
Last edited by robuckj; 11-27-2018 at 05:57 PM.
Reason: Correction
<<I’d like to find a reliable source for some good-quality, ethanol-free gas (intended for road use) to try over several fill-ups, but it is fairly difficult to find.>>
I use:
https://www.pure-gas.org
I used ethanol free for my 340 mile ride home yesterday from northern PA. Got 28 in my sh-awd advanced until I hit NYC metro traffic.
I run Shell 93 and get 17.6 in town and 26.2 on the highway cruising at 75.
The V6 in the SH-AWD TLX did a little better but, it's a more aerodynamic shape than the RDX.
08-11-2018, 06:52 PM
