New 24 Prime mpg checking in

Sometimes, but 76 is low mpg territory. Not that there’s anything wrong with 46.7 mpg

 

Maybe a mile or two better mpg after the car fully breaks in(mostly tires), but that's about what you should expect when driving highway. You get the benefits of the PHEV at lower speeds. If almost your entire trip was 75+mph, you were just driving a slightly heavier regular Prius most of the trip.

I think the EV cutoff for the gen5 Prime is something like 70mph. Anything above that and the ICE HAS to kick on. Plus, you're not going to get the full 40 miles of range at 70mph anyway. At anything close to those speeds, your battery will drain in maybe 20-25 miles. Air resistance is a b!tch as speeds increase.

Prime/PHV: Much more efficient at low speed driving and commutes of less than 40 miles as long as they're not at high highway speeds.
Prius HEV: Slightly more efficient at longer drives at high highway speeds(because no extra battery weight).

 

It's 84mph according to the manual (which would be just below 10000rpm on MG1 by my maths) - it would have been able to do a small fraction of that cruise in EV.

If you were doing 100-mile trips, the EV range of the PHEV is going to give you a significant mpg boost. Out at nearly 300 miles, it begins to become not so significant, and the weight penalty might overtake.

 

Thanks. I should have double checked that.

Have you played with yours to see how much acceleration at those speeds can be done on EV alone until the ICE needs to kick in to help? I have to assume you can get up to 65kph(40mph) on pure EV with most any acceleration except full pedal, but can you do the same up to 100kph(65mph), 120kph(75mph), or 135kph(84mph)? I would guess that once you get up to around 100kph, any serious acceleration will cause the ICE to kick in. Or am I wrong and the EV motors can do it alone even in those speed regimes?

 

Gen 4 Prime gets the same bum rap at speeds above 60 mph. There are some owner that post outliner mpgs to this forum for both the regular Prius (HEV) and the Prime (PHEV). Some are legit and try to explain how they get their numbers, other just dump the numbers with no explanation. Either way, take your pick.

I could explain my best HV mpg trip in the Gen 4 Prime, but it might be boring and useless.
The first half was a 50 mile trip into a 40 mph headwind and about 40 degrees F up from the mid 30s F overnight, which was the really low mpg part of the trip, than the 50 miles back with the tailwind and warmer ambient temps and a warmed up engine, at 60 mph max, but stretches of 50, 40 and some 35 when the engine would shut off often. 50 mpg out into the wind and 91 mpg back with the wind.

And in winter below freezing at 73 mph for a similar 55 mile trip on different roads and typically slightly up in elevation and into a prevailing westerly, yields low 40's mpg for me consistently. The return trip whenever I've double checked is always better mpg, sometimes ( If I stay off the toll road and hwy ) a lot better.

 

No motorways with speed limits above 100km/h around here, so not pushed it that hard in EV. But it will certainly accelerate flat out up to 100-110km/h in full EV.

Unlike the G4, the G5 PHEV is pretty determined to stay in EV. There's no "floor it and the engine kicks in" function any more in EV mode.

MG2's specced as 163hp, which is more than the G4's total hybrid 122hp, so I don't see why there'd be any reason to need the engine to help - I reckon it should be able to stay in EV until it hits the MG1 10000rpm limit.

(The engine will kick in for all the other reasons, like windscreen defrost, or being cold with a low battery. One particular irritating trick it has is to kick in when range drops below about 11km if the weather's freezing - hard to actually get down to "---" on pure EV in winter.)

 

@KMO makes a lot of good points about software thresholds that switch the Primes engine on, in #7
I haven't ever done any EV acceleration trials, but I have taken the Gen 4 (pre 2020 refresh) up to 80 mph EV for about a 1 mile.
I then made a guess at about how long it would take to use all EV range at that speed of between 10 and 15 minutes.
I also broke the front wheels loose once in EV mode, making a left into speeding rush hour traffic.

I've also exceeded the Gen 3 plugins 64 mph threshold a few times by mistake going downhill on the hwy in 70 mph traffic trying to hold it below the engine on limit.

It's not really saying much, but these PHEV's weren't built to break any EV speed or distance records. And it probably doesn't hurt the hybrid batteries all that much, unless an owner runs the car that way all the time until it's out of EV range.

There was a post a few months ago about issue with a Gen 4 hybrid battery after being run out of EV range at 80 mph in EV mode for a couple of years, not surprisingly.

 

For the EPA test, the tires have about 4000 miles of wear on them. The rolling resistance will get better with wear. Depending on when the car was filled, you could have been burning winter blend gas that has less energy. Fuel economy should get better.

Otherwise, you are doing well. My Outback will dip below 30mpg under those conditions.

 

With modern cars like the Prius, the mpg is maximized at the factory. So, the idea of the “break-in” is to preserve the factory mpg, not to improve it.

Since ideally you are supposed to break in at 55 mph but you are actually breaking it at 76 mph, your break-in is actually a trash-in and your mpg will get worse after the first thousand miles or so. Keep driving it at high speeds; it will probably keep getting worse and worse as the car ages. The slower and more gently the cars are driven, the longer they last.

 

My question is, how much of the battery was used?
'40% ratio' means what exactly? It's not a kWh number, right?

So that means 'some' amount of electricity was use to achieve that MPG number.
Which means those kWh's need to accounted for.
Which means the actual MPG number was even less.

This is a Prime and you paid to get to the '90% SOC' number.
If it was not a Prime then the SOC and EV Ratio are meaningless because ALL the energy comes from burning that smelly stuff.

 

The EV ratio is just engine off to engine on; don't know if time or distance. Since the gen4, the hybrid and PHV use the same calculation for it, so doesn't report EV mode use. It means kWhs were used from the battery for the trip, but can't be used to tell if it was a drain, gain, or break even to the battery SOC.

 

From what I've seen, watching it update a bit too much, it seems to be updated once per minute to be "percentage of complete minutes in which the engine didn't start at all".

 

That's your assumption. Is it detailed in the Owner's Manual the way you explain it?
I suspect it's strictly gas mpg and any additional EV propulsion is just icing on the cake, that makes the gas MPG look better because the electrons are not counted.

 

Toyota likely just copied the software from there other cars, as they did with other features, and it in no way accounts for any electricity charged from the grid used.