There is a lot of conversation around the small gas tank and bad gas mileage (and correspondingly low overall range) for the LC250 so I figured it might be useful to address some of the basics around how the forced induction impacts fuel consumption so people can adjust their expectations and behaviors.
"Well anybody who can afford this car, shouldn't care about gas mileage because they can afford the gas!" - Well I most definitely can afford the gas, and premium at that, but being very far off of advertised EPA estimates is worthy of being upsetting even if one can afford to pay for gas and expensive gas even.
"The hybrid system in the LC250 isn't designed for fuel efficiency, but for low end power, so get over it". - Well yes, it's not BIASED toward the explicit goal of extracting maximum fuel efficiency, but by definition, the electric boost results in recaptured energy otherwise wasted and dissipated as heat via the brakes, and instead adds torque and power to the wheels, which necessarily translates to forward motion that otherwise wouldn't exist in the absence of the hybrid system. So either way, it generates more power and forward motion vs a non-hybrid system, even if its BIAS is more for supplementing power or filling holes in the power band while the turbo spools, etc.
"Toyota is silly, their ECO mode isn't actually better for MPGs, put it in Normal or Sport mode". - I love how people extoll the virtues of Toyota engineering and how they are very intentional with design and then decide that they actually programmed ECO mode to be less economical than Normal or Sport because they don't like the slower responses and compensate by being heavy footed during ECO mode and end up keeping the motor in boost a lot and wonder why ECO isn't getting them better mileage. You can't counteract ECO by being lead footed to offset slightly slower responses and acceleration, it's self defeating.
Without splitting hairs too finely and getting down to stoichiometric specifics regarding rich vs lean air fuel ratios run on the T24A - FTS, one can use the engine displacement (2.4L), compression ratio (11.0:1) and various boost pressures of the turbo, to get some understanding of back of the envelope naturally aspirated equivalent for various boost pressures from the turbo. After all, engines and the way they generate power is all just a giant pump of air and fuel. Think of the turbo as displacement on demand. So here we go:
1) No boost - 2.4L engine
2) 10 PSI boost - 4.03L engine
3) 15 PSI boost - 4.85L engine
4) 20 PSI boost - 6.07L engine
So if you're easy on the pedal and more importantly in ECO mode and driving smoothly (vs abruptly accelerating and winding up the turbo boost pressures), it consumes the fuel equivalent of the above stated naturally aspirated engines at the various loads described. If you're constantly at 10 PSI of boost, you're roughly ingesting and burning up the air/fuel of a 4L engine for those moments. The car is too heavy and big to be operating as solely a 2.4L 4 cylinder, for lots of the time, but to be under low single digits of boost for periods vs 10+ lbs makes quite a difference for fuel economy. I never hesitate to call on its full power when I need to accelerate quickly, I am merely pointing this out to the countless people who are confused as to why their fuel economy is low when they wind up the motor quite often and spend a lot of time in boost. Separately, the hybrid electric assist can also be thought of as additional displacement equivalent roughly equating to ~0.8L across the entire range. so factor that in as well (but this doesn't cost us any additional fuel, so is really quite a neat perk). Now add that back in and suddenly being a 2.4L supplemented by a 0.8L of equivalent electric power sounds a lot more reasonable at 3.2L displacement equivalent.
Fuelly shows an average of ~19 MPGs mixed for the LC250 and I think between this forum and that site, there is selection bias for LC/car enthusiasts that have a penchant for modifying their cars and in the case of the LC, typically upsizing their wheels and tires and lifting them, adding armor etc, which reduces MPGs. With stock suspension and tires, the LC has no issues being able to reach its EPA ratings if driven reasonably, and without calling on its full power potential constantly.
