4RX Mileage Thread
07-26-21, 05:12 PM
#332
I was trying to find out how traffic light stops impact my MPG (I know they do but curious to what extend) and instead came across this - turns out the faster you go above 50mpg, the more "fuel penalty" you pay. And it seems pretty significant. According to www.fueleconomy.gov, if you go 80Mph on a highway (specifically in RX 350), you are burning 50% more fuel than if you went 50Mph.. pretty crazy. See attached pic - I entered $2.90 cost of a gallon I pay here locally and the chart is showing how much more I'm paying (hypothetically) for gas when going faster than 50Mph. At 80Mph it's almost 50% increase. Of course cost of the gas is the same, it simply shows drop in efficiency.
07-27-21, 07:50 AM
#333
came back from a 1200 mile road trip with our new RX350 F Sport Handling
Went to Sequoia and Kings Canyon NPs then drove to Bay area and heading down to OC via highway 1, overall the RX did great, the ride was very comfortable, and it handled great driving in the winding mountain roads of the Sequoia forest. But the car is underpowered especially with 4 passengers and luggage going uphill, and i can now definitely feel the hesitancy of the 8 speed auto people have been complaining, a reprogrammed version of the same transmission would do wonders for this SUV even without upgrading the engine. Wish we would've gone with the RX450h instead, the instant torque of the hybrid motor would be greatly appreciated. Overall we averaged about 21 mpg in mix driving.
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raylor4 (07-27-21)
07-27-21, 08:31 AM
#334
Enjoy your beautiful RX! Thanks for the post on the handling. Great to hear.
10-06-21, 08:05 PM
#335
We've had my wife's 2020 RX 350 for a year now. At 8,000 miles, the overall actual MPG clocks in at a solid 25.5 on a combination of 70% Highway/30% City. On the highway, we're getting about 30 MPG; in the city, about 15 MPG. Our city MPG suffers from short trips in stop-and-go traffic. MPG has been higher in the summer than the winter. No surprise there.
10-06-21, 08:47 PM
#336
Intermediate
We've had my wife's 2020 RX 350 for a year now. At 8,000 miles, the overall actual MPG clocks in at a solid 25.5 on a combination of 70% Highway/30% City. On the highway, we're getting about 30 MPG; in the city, about 15 MPG. Our city MPG suffers from short trips in stop-and-go traffic. MPG has been higher in the summer than the winter. No surprise there.
10-07-21, 01:34 PM
#337
10-07-21, 08:32 PM
#338
Results of long term 87/93 octane test
I recently completed a long term test of 87 octane and 93 octane fuels in my 2020 RX350 base. The test was performed for my own use and I'm publishing it here for any others that might find it useful. The intent is not to convince anyone that one fuel better than another. Make your own decisions using your criteria, as I have. Presented below are Results, Methodology and Limits/Variables sections.
RESULTS
METHODOLOGY
I ran 12 full tanks of 87 octane through my RX, then switched to 93 octane and ran 10 full tanks of 93 octane. I then switched back to 87 octane for a couple of tanks, primarily to again assess performance driving characteristic differences. These last two tanks of 87 octane were not included in the mileage calculations. All but one of the fill-ups came from Top Tier brands. All calculations were performed by hand, although I also tracked RX indicated mileage. Nearly all the driving was performed in normal mode. A small percentage of miles running 87 octane were driven in Sport mode. No 93 octane miles were driven in Sport mode.
LIMITS and VARIABLES
Performing this test took a back seat to living my life. I made reasonable effort to make it a good test, but make no pretense that it was extremely rigorous or reliably repeatable. Following are a few variables and limits to the testing, along with my best guess regarding their effect.
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If you made it this far, thanks for taking the time to read. I'm happy to entertain comments or answer questions.
RESULTS
Fuel Mileage
87 Octane: averaged 23.0 MPG over 3,711 miles
93 Octane: averaged 23.6 MPG over 3,310 miles (2.6% better than 87 octane)
Note that in my area 93 Octane is routinely $.60 more per gallon than 87 octane at Top Tier stations. Over the course of the test I averaged paying $2.91/gallon for 87 octane, so 93 octane costs 20.6% more. Factoring in the improved mileage, the net cost of 93 octane is 17.6% higher than 87 octane over 1,000 miles.
Performance
Absent a rigorous testing regime and specialized equipment, determining driving characteristic differences requires very subjective analysis. I went back and forth during the test transitions, thinking I could notice a performance difference sometimes and not others. In the end I concluded that improved performance using 93 octane is probably measurable, possibly noticeable, but definitely not material. Even if performance improves at a rate 2x mileage, it would still only be about 5%. My intuition tells me that performance and mileage differences likely track more closely than that.
RX fuel mileage indicator
The RX MPG indicator was a little more inaccurate compared to hand calculations for a single tank than I expected. I found variances up to +- 2 MPG compared to hand calculations, though most were in the +- .5-1.3 range. Note, though, that in the aggregate the RX MPG indicator was very accurate; only .1 MPG different than the hand calculations.
.87 Octane: averaged 23.0 MPG over 3,711 miles
93 Octane: averaged 23.6 MPG over 3,310 miles (2.6% better than 87 octane)
Note that in my area 93 Octane is routinely $.60 more per gallon than 87 octane at Top Tier stations. Over the course of the test I averaged paying $2.91/gallon for 87 octane, so 93 octane costs 20.6% more. Factoring in the improved mileage, the net cost of 93 octane is 17.6% higher than 87 octane over 1,000 miles.
Performance
Absent a rigorous testing regime and specialized equipment, determining driving characteristic differences requires very subjective analysis. I went back and forth during the test transitions, thinking I could notice a performance difference sometimes and not others. In the end I concluded that improved performance using 93 octane is probably measurable, possibly noticeable, but definitely not material. Even if performance improves at a rate 2x mileage, it would still only be about 5%. My intuition tells me that performance and mileage differences likely track more closely than that.
RX fuel mileage indicator
The RX MPG indicator was a little more inaccurate compared to hand calculations for a single tank than I expected. I found variances up to +- 2 MPG compared to hand calculations, though most were in the +- .5-1.3 range. Note, though, that in the aggregate the RX MPG indicator was very accurate; only .1 MPG different than the hand calculations.
METHODOLOGY
I ran 12 full tanks of 87 octane through my RX, then switched to 93 octane and ran 10 full tanks of 93 octane. I then switched back to 87 octane for a couple of tanks, primarily to again assess performance driving characteristic differences. These last two tanks of 87 octane were not included in the mileage calculations. All but one of the fill-ups came from Top Tier brands. All calculations were performed by hand, although I also tracked RX indicated mileage. Nearly all the driving was performed in normal mode. A small percentage of miles running 87 octane were driven in Sport mode. No 93 octane miles were driven in Sport mode.
LIMITS and VARIABLES
Performing this test took a back seat to living my life. I made reasonable effort to make it a good test, but make no pretense that it was extremely rigorous or reliably repeatable. Following are a few variables and limits to the testing, along with my best guess regarding their effect.
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Driving type - as a retired guy, my driving habits are rather predictable. I tend to do a lot of trips in the 18-30 minute range, with some traffic, and occasional 3 hour drives into the WV mountains. I kept comments on each tank of fuel, noting any longer trips driven. The net is that I don't think there are big differences in the types of miles driven between the two octane tests. Note that I was essentially the only RX driver during the testing range. My wife may have driven a little, but definitely under 50 miles of the 6,300 miles in the test.
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Weather - testing began in April and concluded in early October. I understand that temperature and humidity can affect mileage and performance, but have no reason to think that the results were affected by the weather. No snow, muddy or flooding conditions were encountered during the test.
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Bike rack and bike hauling - I put a Curt hitch and a 1UP single-bike rack on my RX around the same time as the 93 octane test began. The hitch + rack added about 50 pounds of sprung weight to the RX. I don't think that's enough to matter. Aerodynamics are another matter. I'm not an aeronautical engineer or well-versed in fluid dynamics, but do have a basic understanding of the coefficient of drag and how difficult it is to assess impacts to that coefficient, especially on the trailing edge of a body. A couple of things led me to conclude that the rack and occasional bike hauling didn't negatively affect the 93 octane testing results. First, the rack folds up close to the RX rear bumper when not in use, and is about the same height as the bumper. Second, I ran two tanks of 87 octane through the RX at the end of the test, as previously noted, and hauled my bike for some of those miles. My mileage for those two tanks was 23.5, better than the overall 87 octane mileage and only .1 MPG lower than the 93 octane average. (Recall from previous comments that I did not include these two tanks of gas in the reported results.)
.If you made it this far, thanks for taking the time to read. I'm happy to entertain comments or answer questions.
Last edited by bamalam; 10-10-21 at 07:05 AM.
10-09-21, 10:59 AM
#339
Very nice, thorough test and report -- thanks for doing it.
11-15-21, 10:12 PM
#340
Driver School Candidate
2022 Mileage - UGH
My new 2022 RX has less than 600 miles on the odometer. I’m running in ECO mode and dash states mileage average of 17.7mpg. I’ve fueled up 3x already (plus that free tank!), once on empty! UGH! It’s probably 65-70% small town driving but dang. My trusty 2013 RX averaged 22 city/highway. Is there a break-in period or is this one an expensive dud?
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happychris (12-09-21)
11-15-21, 11:37 PM
#341
There is a fuel pump inside your fuel tank, that depends on being submerged in gas to keep cool. Do NOT run the tank to near empty, as you could burn out that pump and end up (a) stranded and (b) with a big tow + repair bill.
17.X mpg is pretty low, even for stop and go town driving. I seem to recall that mine got better after the first couple of thousand miles. I would look for an opportunity to take a longer drive on highway or rural roads, and see whether it goes up over 20. And also do the calculation yourself, to verify what the dashboard is reporting. I checked mine that way, and found that the reported fuel mileage was very accurate, but that doesn't mean every unit is equally reliable.
Finally, I don't know for a fact whether "Eco" mode actually improves fuel mileage or not. I never use it, as I hate the sluggish performance. The stock throttle response is bad enough in normal mode. Mine gets 21-23 mpg in suburban driving, and I've seen 28 on a highway trip using cruise control a lot.
There's a forum thread all about fuel mileage here.
17.X mpg is pretty low, even for stop and go town driving. I seem to recall that mine got better after the first couple of thousand miles. I would look for an opportunity to take a longer drive on highway or rural roads, and see whether it goes up over 20. And also do the calculation yourself, to verify what the dashboard is reporting. I checked mine that way, and found that the reported fuel mileage was very accurate, but that doesn't mean every unit is equally reliable.
Finally, I don't know for a fact whether "Eco" mode actually improves fuel mileage or not. I never use it, as I hate the sluggish performance. The stock throttle response is bad enough in normal mode. Mine gets 21-23 mpg in suburban driving, and I've seen 28 on a highway trip using cruise control a lot.
There's a forum thread all about fuel mileage here.
Last edited by dibl; 11-16-21 at 12:33 AM.
11-16-21, 03:28 AM
#342
Pole Position
How To Fill For MPG Calculation
How do you guys fill the tank for MPG calculation? I’ve been “superfilling “ to the point where I can see gas inside the top of the filler pipe. Somewhere I recall reading that driver’s shouldn’t do that. But how else can you be sure you’re filling the tank to the exact same point to get an accurate MPG calculation?
On another note, here is a data point: I've been getting 23 to 25 MPG from Pittsburgh to Indianapolis (750 miles round trip) and back over 4 trips. At just under 80MPH (which is actually slow compared to most traffic on I-70). 2020 RX350 with AWD. I would imagine I could get closer to 30 MPG if I drove 65 MPH. I might try that and see. My old 2009 LS400 once got 30MPG on a similar trip at 55MPG, but that required premium gas.
I get 17-18 around town in Pittsburgh. Pretty good. For a chuckle/reference, my first car, a 1969 Buick LeSabre, got 8 MPG around town on “high test” gas.
On another note, here is a data point: I've been getting 23 to 25 MPG from Pittsburgh to Indianapolis (750 miles round trip) and back over 4 trips. At just under 80MPH (which is actually slow compared to most traffic on I-70). 2020 RX350 with AWD. I would imagine I could get closer to 30 MPG if I drove 65 MPH. I might try that and see. My old 2009 LS400 once got 30MPG on a similar trip at 55MPG, but that required premium gas.
I get 17-18 around town in Pittsburgh. Pretty good. For a chuckle/reference, my first car, a 1969 Buick LeSabre, got 8 MPG around town on “high test” gas.
Last edited by daryll40; 11-16-21 at 03:38 AM.
11-16-21, 04:47 AM
#343
BTW several forum users have been examining the mileage effect of using one of the higher octane gasolines (89, 91, 93). If you can stand 30 or 40 cents more per gallon, for the experiment, it would be interesting to hear how your car performs on that 750 miles trip. (No one thinks it is cost effective, but it's a matter of curiosity as we've recently found that the RX 350 and 2GR-FKS specs were obtained by Lexus using 91 octane fuel, according to wikipedia.)
11-16-21, 08:52 AM
#344
Pole Position
I'll think about using premium on my next trip. I dunno...it sounds like the cost of the better gas is higher than the value of the extra MPGs. What really caught my eye here was the hugely improved mileage at 50MPH vs 80MPH. While I can't drive 50MPH on I-70 through Ohio (they'll arrest me!!!), I can maybe do the experiment at 65MPH. I've done the trip enough times at 79-80MPH to have that (24MPG) as a good reference. Looks like the trip will take about 6 and a half hours at 65MPH, versus 5 and 3/4 hours at 80MPH. I'd save about $20 roundtrip, but would take 1.5 hours (roundtrip) longer.
I used to have a 2009 LS400AWD. The car was supposed to use 91 octane. I played with 87, 90 (by mixing 87 and 93) and 93. For THAT car, the best value was 90 octane doing the mix. 89 cost the same as 90, but to get it you have to do the mix at the pump each time.
I used to have a 2009 LS400AWD. The car was supposed to use 91 octane. I played with 87, 90 (by mixing 87 and 93) and 93. For THAT car, the best value was 90 octane doing the mix. 89 cost the same as 90, but to get it you have to do the mix at the pump each time.
12-07-21, 01:04 PM
#345
Gas mileage in winter ??
I have a 2021 RX350 and I would say in the last 2-3 weeks my gas mileage average has gone down. For example I usually average 17.1 mpg as I just drive back and forth to work and its only about five miles one way with no highway so not expecting any big numbers. but recently it has dropped to about 14.1 as the average, is this due to the winter months with the winter gas additives as I am in Pittsburgh, PA? Just wondering if any one else has experienced such a drop.