bclexus

Still searching to reveal the mysterious cause of the defective (faulty) data.

bclexus

So, as the mystery of the data discrepancy continues I have put 50 additional miles on my car, which is 350 miles since last refueling.

This additional 50 miles caused the fuel gauge to drop quite drastically from just under ¾ tank (say 13/16 tank) to ½ tank or a drop of over ¼ tank (say 5/16 tank drop), representing a drop of ~5.6 gallons. 5.6 gallons to travel 50 miles is a miserable 8.9 mpg, which of course is not accurate.

The mpg (since last refuel) dropped from 29.4 mpg at 300 miles traveled to 28.3 mpg at 350 miles traveled, or 12.4 gallons used to travel 350 miles with the fuel gauge now at ½ tank. But a reading of half a tank can't be correct if I used 12.4 gallons of a 17.4 gallon tank! If the fuel gauge is correct (which it can't possibly be accurate!) it supposedly took half tank or 8.7 gallons to travel 350 miles (not 12.4 gallons as the mpg data calculates). I therefore should have half a tank remaining or 8.7 gallons left in the tank.

There's no doubting that the 350 miles traveled (as displayed by the cumulative primary odometer and the Trip A odometer that was reset at fill-up) is the only accurate piece of data.

The data provided by the car's onboard information that I think is inaccurate and highly questionable: (a) the fuel gauge accuracy (highly unlikely!) and (b) the amount of fuel actually used according to the mpg data (highly questionable!), and (c) the mpg data itself (also very questionable!). If the 28.3 mpg data for 350 miles traveled is accurate then 12.4 gallons were used to travel those 350 miles, leaving just 5 gallons remaining in a 17.4 gallon tank - yet the fuel gauge is displaying ½ tank, which is more like ~8.7 gallons.

Any way you slice it the numbers come out upside down and inside out!

703

Unfortunately that’s how Lexus has designed the common float sensor used across their range. Depending on the shape of the tank, you get a non linear reading. It’s nothing but a simple float device.

bclexus

That may answer for the fuel gauge discrepancy, but not the mpg data the vehicle provides. The only thing I have any trust in with this subject matter is the mileage driven (definitely not the range) because I believe vehicle odometers must be accurate to conform with mandated regulations.

bclexus

dkp993 - I have driven 420 miles since fill-up and my fuel gauge is still registering 1/3 tank remaining. According to the data I'm averaging 29 mpg since last refueling, which 'if accurate' is right on the mark for estimated city driving and computes to 505 miles per 17.4 gallon tank. My Range says I currently have 120 miles remaining, which 'if accurate' would give me 540 miles per tank of all city driving, which is well above the Lexus estimate of 505 miles for city driving at 29 mpg.

The estimated highway mpg is 34 mpg, which computes to 592 miles per 17.4 gallon tank.

It will be interesting, as time goes by, to see if the mpg, the fuel gauge reading, the range and the mileage driven all coalesce to provide data that makes sense. I'm really not counting on that happening! Because I perceive that only the mileage driven as registered on the odometer can really be trusted as being accurate. Maybe the mpg and maybe the range are accurate, but maybe not... I definitely don't think the fuel gauge can be trusted...

dkp993

Nice! You’re probably doing more city driving then I do but it’s not hugely out of line with what I’ve been seeing. I bet if I slowed down on the freeway I stretch it to the upper 400’s pretty easily.

bclexus

Thanks! Yeah, my actual results, along with your results you shared, makes me feel good about my car's health being sound.

bclexus

Well, I've driven over 500 miles in all city stop-n-go driving averaging about 29 mpg (according to the data info) and I still have just under ¼ tank of gas left and over 60 miles of range remaining (according to the data info). Is almost a ¼ tank of gas a couple of gallons or 3-4 gallons? I think I could easily get 570 miles out of a full tank of gas in all city stop-n-go driving, which computes to about 33 mpg, beating the EPA rating of 29 mpg for city driving by 4 mpg. But I don't want to test my luck and run out of gas seeing the maximum mileage I can get out of a full tank...

I suspect I could probably get as much as 630 miles out of a full tank of gas with all highway driving, achieving about 36 mpg and beating the highway driving EPA rating of 34 mpg by 2 mpg. I think that is very likely considering it appears I can easily get about 570 miles out of a full tank of gas with all city stop-n-go driving and 33 mpg.



Very pleased!

bclexus

It's a real shame Lexus discontinued the GS model, and the GS 450h model in particular...

bclexus

I filled-up yesterday with 15.2 gallons of 93 octane premium Tier 1 gasoline - so with the car's 17.4 gallon fuel tank I guess I really did have only about 2 gallons of gas remaining when the fuel gauge displayed a tad under ¼ tank and a range of about 60 miles remaining. Those ~2 gallons of gas at ~29.4 mpg would indeed be a range of about 60 miles before running out of gas.

So, now I know that just under ¼ tank of gas equals about 2 gallons of gas - that seems to be fairly accurate. And a range of about 60 miles with 2 gallons at ~29.4mpg is also fairly accurate.

However, after I filled-up, my mileage range was only 395 miles, 15 miles more than the 380 mileage range I had the last time I filled-up, but still far lower than the 505 mileage range you usually have after filling-up. That's rather strange and unexplainable. I made it a point to reset all fuel mileage data and clear the trip fuel consumption data before filling-up. I'm not sure what the full tank mileage range is actually based on (since I reset/cleared all data available)...unless it is based on some old data still being retained. Maybe my full tank mileage range will continue to adjust upwards in the future!

dkp993

My guess, and it’s exactly that, is that the computer calculates that expected range based on the previous MPG’s and driving style. It going up 15 miles from the last reading supports my theory (guess). I would bet if you continue to drive the way you have at each fill up that estimated range increases.

bclexus

That's my guess too. If true however, resetting and clearing the current/previous data doesn't totally eradicate it.

bclexus

My last fill up gave me a range of 410 miles, so it continues to increase a little each time. I think the range must be based on an amalgamation of factors, not just one single factor.

bclexus

I have yet to take a trip of any length, so I don't know from monitoring how the ICE and the traction motor react when just maintaining a speed (i.e cruising) on level ground with no headwind.

For example, say traveling at 70mph - what percentage of the time is just the ICE engaged to propel the car? Is there ever a time when the ICE drops out and just the traction motor propels the car at 70mph for any period of time?

At what time-point or circumstance/condition does the ICE drop out (similar to what happens at much slower speeds and light/mild throttle demands)?

bloodbean

I've only had my 2013 GSh about 3 months (2k miles) and haven't seen it only use the traction motor above 50mph.

Although a 2018 would surely have better condition batteries so would be interested to hear how yours does at higher speeds.