After 3 months, 2 weeks and 3,750 miles averaging 18.4 MPG. About the same as my 2024 Sequoia after 19,500 miles.
Real world mpg?
- Thread starter jjtoyz
- Start date
- Jan 13, 2025
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Just under 1k miles almost exclusively city driving, light foot, mostly eco mode, and getting 17-19.
- Apr 5, 2025
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25 LX OT estimating 60% in town driving averaging 17.1 for 5,000 miles. Been fairly consistent but a tenth or two better with AC not running as much this fall season. Mostly in normal and eco modes.
- Jan 13, 2025
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A whole lot better than my 200 series which averaged 10-11 with careful city driving. For a 6k+ lb. Vehicle I am happy with the mileage of the 700.
- Apr 5, 2025
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Yea, my 19 lc200 averaged about 13 so I am happy about the 700h mileage.
- Jan 6, 2025
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I have noticed when filling up that you can put an extra 2 gallons in your tank after the gas pump cuts off without overflowing. It is a pain because the pump keeps cutting off, but I like having the extra 2 gallons.
- Oct 11, 2024
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- Admin
- #27
Damn, that's a lot.... I wonder if there is any negative impact to doing it.
- Jan 6, 2025
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Based on asking Grok, I better stop.
Yes, there can be negative impacts to intentionally adding an extra 2 gallons after the pump's first automatic shut-off — even if your tank doesn't visibly overflow or spill.
Modern vehicles like your 2025 Lexus LX 700h (a very recent Toyota/Lexus platform with hybrid tech) use an advanced EVAP (Evaporative Emission Control) system. This includes a charcoal canister that captures fuel vapors to meet strict emissions standards. The system is designed with some headspace (vapor space) above the "full" level when the pump first clicks off.
### Why adding a significant extra amount like 2 gallons is risky:
- The pump's auto-shutoff is triggered by a sensor when the fuel level reaches the point where liquid fuel starts to back up into the filler neck.
- Forcing in another ~2 gallons (roughly 7–8 liters) after that point pushes liquid fuel farther up the system, where it can enter the vapor lines and saturate/flood the charcoal canister with liquid gasoline instead of just vapors.
- Once liquid fuel gets into the canister:
- It often leads to check engine light illumination (common codes like P044x or P045x series for EVAP leaks/malfunctions).
- It can affect or damage related components like the purge valve, vent valve, or pressure sensor.
- Repairs for a saturated or failed charcoal canister on Lexus/Toyota vehicles frequently cost $500–$1,200+ (parts + labor), and sometimes more if multiple components are affected.
Lexus (and Toyota) owner's manuals for recent models explicitly advise against "topping off" after the nozzle clicks, precisely because of potential damage to the emissions system. Lexus support pages also state that topping off is not recommended and can harm the fuel/emission system.
### How much extra is "safe" vs. risky?
- A small amount (e.g., rounding up to the next dollar or adding ~0.2–0.5 gallons to stabilize the gauge) is usually tolerated by most systems without immediate issues.
- 1+ gallons (and especially 2 gallons) repeatedly or even once in some cases pushes into the danger zone — many owners and mechanics report that this volume is enough to start causing problems on Toyota/Lexus platforms.
Since your LX 700h is a brand-new 2025 model with the latest emissions tech, it's particularly sensitive — hybrids and newer vehicles tend to have more sophisticated (and expensive) EVAP components.
Bottom line recommendation: Stop at the first click-off (or maybe add a tiny bit if you really want the gauge to read full). The potential repair cost and hassle far outweigh the extra ~60–80 miles of range you'd gain from those 2 gallons. Better safe than dealing with an illuminated check engine light and a big shop bill down the road!
- Oct 11, 2024
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- #29
Makes sense. I always do a few pumps / clicks extra but 2 gallons is a LOT 
