Prius fuel management question

Hector Island

Hi folks,

I recently bought a 141D Prius Japanese import and I love the car, but an important selling point for me was that it would cost less in petrol. In my old Yaris, I could get roughly 535km per tank - I drive about 100km a day, using the M11 too.

Now I'm getting between 600-700km per tank, but I thought I'd get more.

What are the ways I can use the car to save even more fuel? Or is it wrong to think I can save much more, when most of my driving is along the motorway?

I know this was probably asked before, but I don't know how to search for it if it has. Thanks in advance!

colm_mcm

Do you know how big the tank is, and how much more economical did you think the much bigger and heavier Prius would be?

Hector Island

colm_mcm wrote: »

Do you know how big the tank is, and how much more economical did you think the much bigger and heavier Prius would be?

I don't know how big the tank is, Colm, but I can fill it with about €45, whereas I could fill the Yaris with €50. As for how much more economical, I didn't have a figure in mind, but I read claims by people who were going weeks without a refill, but that was basically because they weren't driving at speeds. I have to use the motorway, so I suppose that's probably why I'm only going days, and not weeks, before I refill...

colm_mcm

If your figures are correct and it only takes €45 to fill the tank, that’s 32l (assuming €1.40 a litre) so 32l/700km = 4.5l/100km = 63mpg.

colm_mcm

Quick google says the tank is 43l, so 6.1l/100km or 46mpg, which isn’t that great

ELM327

We had a mk2 prius and it wasnt great on fuel. Low 50s or high 40s. My diesel of the same age was better

I had thought the newer ones would be better!

kaahooters

if you want better fuel econemy , learn how to hypermile, it dosent work well in ireland, cos, hills, but it might get you 5% more per tank.

both fuel tanks are 42 liters, by the specs anyway, and your complaning that the prius, a car that is twice the size of the yaris, only get you 100km a tank more?

colm_mcm

I would suppose that takes of 70mpg have given the OP unrealistic expectations?

grogi

The solution is to get a bigger tank... Prius can get up to 2000km on single tank, provided it is big enough...

grogi

colm_mcm wrote: »

Quick google says the tank is 43l, so 6.1l/100km or 46mpg, which isn’t that great

That would require the op filling the car with completely dry tank...

Lantus

There are plenty of sites like honest John which collect data on real world efficiencies and hybrids like the Prius generally provide a slight improvement over petrol where the driving style and mileage are optimised. So some driving at 40 to 80km/hr and lots of urban suits them best where the battery gives that initial push before the petrol takes over.

Advertising is terribly good at manipulating people into buying stuff. A recent Toyota ad had one Mum proudly claim 2 months of driving on a single tank. Which is meaningless and misleading.

If you are getting 1.5l/100km improvement over an equivalent petrol then your probably doing well.

Hector Island

kaahooters wrote: »

if you want better fuel econemy , learn how to hypermile, it dosent work well in ireland, cos, hills, but it might get you 5% more per tank.

both fuel tanks are 42 liters, by the specs anyway, and your complaning that the prius, a car that is twice the size of the yaris, only get you 100km a tank more?

I'm not necessarily complaining - although obviously I'd like even more out of the tank - but I'm wondering if there's a way of getting more. For instance, the Brake Engine gear B on the stick slows the car going downhill to help the brakes, apparently - but it's worse on fuel than if I leave it in D, you know? I've been more mindful of trying to control how I cruise at speed, keeping an eye on the km per litre symbol on the dash.

Sometimes driving the same route, I'm getting less, so I might be too heavy on the pedal, but it seems that the hype about people refilling every few months has led me into thinking it works also when you're driving motorway every day, and through the Wicklow Mountains.

Thanks everyone for the answers, by the way!

Chippy01

I've had a gen 3 Prius for quite a few years now (UK import, not Japanese), and have a couple of things you can ponder over.

First off, don't believe all the hype (''I only fill up every couple of months'') - The owner probably only does 50kms a week taking their kids to school, or has the plug-in variant that can do slightly more kms on battery only than the 'standard' Prius, especially if used exclusively in towns.

You will get better fuel economy in the summer than the winter.
As an example, my usual run to work is 60kms each way with the cruise set around 105kmh, 95% of the journey on dual carriageway. My tank average is usually somewhere between 4.7L/100km to 4.3L/100km (60 - 65mpg in old money)
My very best tankful was 3.8L/100km (about 74mpg), but that week I was working in a different area, and the posted speed limit never went above 80kmh, and it was a very fine and sunny week in May
So although it's drag co-efficient is low, as with any vehicle the faster you go, the more fuel you'll use.

Put a couple of extra psi into your tyres, and check the pressures frequently. I run mine at 38psi all round. Also make sure your tyres are rated A or B for rolling resistance. That will probably mean more premium priced tyres as cheaper tyres usually have a higher rolling resistance.

Use the correct engine oil rated by Toyota. IIRC it is 0W/20. If a generic oil like 5W/30 is used, you will notice a drop in economy.

Think ahead when driving. Although braking will charge the traction battery, it is still fuel wasteful. So try driving in such a way that braking is kept to a minimum. Your traction battery will still be charged when driving, and just by easing off and letting the car 'coast' (for want of a better term) while still in D will also charge the traction battery.

B mode is basically engine braking, albeit slight. Handy for slowing down quicker than the coasting method, but slower than actual braking. Although you can, it's preferable not to drive normally in B mode.

PWR mode sharpens engine response, but will use more fuel. But it does give you the extra kick if you want to overtake in a hurry.

ECO mode tightens and slows engine response, and you can feel it in acceleration, and on the pedal. This mode is probably better used in towns, but I never use it, as I am not normally driving in town traffic.

D mode is what I would class as a 'normal' setting.

Remember it's still a 1.8 litre engine under the bonnet.

Oh, and the fuel tank on the Gen 3 is 45 litres, not 43 as mentioned in a previous post. I believe the new Gen 4 Prius has the 43 litre tank.

grogi

Hector Island wrote: »

I'm not necessarily complaining - although obviously I'd like even more out of the tank - but I'm wondering if there's a way of getting more. For instance, the Brake Engine gear B on the stick slows the car going downhill to help the brakes, apparently - but it's worse on fuel than if I leave it in D, you know? I've been more mindful of trying to control how I cruise at speed, keeping an eye on the km per litre symbol on the dash.

Sometimes driving the same route, I'm getting less, so I might be too heavy on the pedal, but it seems that the hype about people refilling every few months has led me into thinking it works also when you're driving motorway every day, and through the Wicklow Mountains.

Thanks everyone for the answers, by the way!

Yes, B is worse on fuel overall. As is touching the EV button. B-mode is designed for driving in mountainous areas, where engine breaking is crucial for keeping the brakes operational.

Pulse and glide is a great way of increasing the economy. Google it, it is well described in hundred other places.

CoBo55

grogi wrote: »

Yes, B is worse on fuel overall. As is touching the EV button. B-mode is designed for driving in mountainous areas, where engine breaking is crucial for keeping the brakes operational.

Pulse and glide is a great way of increasing the economy. Google it, it is well described in hundred other places.

Pulse and glide me hole, in other words you'd be better off with a diesel... Why are people falling for the hype? I genuinely don't understand why, have petrol engines suddenly stopped producing vast amounts of co2?

zilog_jones

colm_mcm wrote: »

Quick google says the tank is 43l, so 6.1l/100km or 46mpg, which isn’t that great

But if the OP is only filling it with €45 it's nowhere near a full tank. They need to record how many actual litres are going in at the pump otherwise it's all guesswork.

Also, something to note with the gen 3 Prius: When the fuel gauge goes down to the last bar and starts flashing there are still 9 litres left in the tank. So, once this happens, reset your trip counter and drive another 50 miles before filling

Hector Island wrote: »

I'm not necessarily complaining - although obviously I'd like even more out of the tank - but I'm wondering if there's a way of getting more. For instance, the Brake Engine gear B on the stick slows the car going downhill to help the brakes, apparently - but it's worse on fuel than if I leave it in D, you know? I've been more mindful of trying to control how I cruise at speed, keeping an eye on the km per litre symbol on the dash.

B is for engine braking so you don't cook your brakes on long descents, not for efficiency.

Chippy01 wrote: »

You will get better fuel economy in the summer than the winter.
As an example, my usual run to work is 60kms each way with the cruise set around 105kmh, 95% of the journey on dual carriageway. My tank average is usually somewhere between 4.7L/100km to 4.3L/100km (60 - 65mpg in old money)
My very best tankful was 3.8L/100km (about 74mpg), but that week I was working in a different area, and the posted speed limit never went above 80kmh, and it was a very fine and sunny week in May
So although it's drag co-efficient is low, as with any vehicle the faster you go, the more fuel you'll use.

This is pretty much my experience too. I have the Plug-in, but at speeds over 85 km/h I don't benefit from that anyway. There's a significant difference in fuel consumption between 100 and 120 km/h for example. If I stick to 120 km/h (130 indicated, the speedo lies as much as the fuel gauge ) I'll get about 50 MPG or 5.6 l/100km, but going down to 100 km/h I get closer to the above.

Put a couple of extra psi into your tyres, and check the pressures frequently. I run mine at 38psi all round. Also make sure your tyres are rated A or B for rolling resistance. That will probably mean more premium priced tyres as cheaper tyres usually have a higher rolling resistance.

Yes, low rolling resistance tyres do make a difference, although you're only talking 1-2 MPG at most.

Use the correct engine oil rated by Toyota. IIRC it is 0W/20. If a generic oil like 5W/30 is used, you will notice a drop in economy.

I've gone between the two and noticed no difference really. Most dealers in Ireland will only stick in 5W30 unless you ask/pay more.

grogi wrote: »

Pulse and glide is a great way of increasing the economy. Google it, it is well described in hundred other places.

Pulse and glide only really works at speeds up to around 67 km/h (about 74 indicated? I forget) in the 3rd gen Prius. No good for motorway driving.

Hector Island

I actually use the pulse and glide - without knowing what it was, I had to google it after it was mentioned here. My big caveat with it is, maybe the pulse costs more than the glide gains? But anyway, along the motorway, it's necessary to inject some pace and keep the traffic progressing. I agree with zilog above that P&G works great at about 67km/h, where I can keep the car in ECO mode, though I also find that a light pedal in ECO mode and can slowly gain speed for the car and get it to a high-ish speed, but of course on the N11 heading to Wicklow, I tend to lose all that when I need to climb...

Hector Island

Chippy01 wrote: »

ECO mode tightens and slows engine response, and you can feel it in acceleration, and on the pedal. This mode is probably better used in towns, but I never use it, as I am not normally driving in town traffic.

Thanks Chippy01!

Actually, just reading my last reply, I mention using ECO mode, but really what I mean is that on the dash, the ECO light comes on at certain times, depending on how I'm using the pedal. But I see there's an ECO mode button, as well as an EV Mode, and PWR Mode. I never push these buttons in! Perhaps I should?

Chippy01

zilog_jones wrote: »

Also, something to note with the gen 3 Prius: When the fuel gauge goes down to the last bar and starts flashing there are still 9 litres left in the tank. So, once this happens, reset your trip counter and drive another 50 miles before filling

When that last pip flashes, it's best to fil up asap. That 50 miles can easily be cut via strong head winds, heavy weather, etc. I've heard it's not advisable to run out of fuel in a Prius


Yes, low rolling resistance tyres do make a difference, although you're only talking 1-2 MPG at most.

Maybe, but as Mr Tesco says, every little helps


I've gone between the two and noticed no difference really. Most dealers in Ireland will only stick in 5W30 unless you ask/pay more.

I noticed the difference within a week of a service. Went back and had them change the oil for the correct grade. No extra charge, and my car returned to normal operations.

.

Chippy01

Hector Island wrote: »

Thanks Chippy01!

Actually, just reading my last reply, I mention using ECO mode, but really what I mean is that on the dash, the ECO light comes on at certain times, depending on how I'm using the pedal. But I see there's an ECO mode button, as well as an EV Mode, and PWR Mode. I never push these buttons in! Perhaps I should?

A quick google came up with this explanation. It's from a U.S. site, but the basics is there (albeit in U.S. speak)

https://prius.fandom.com/wiki/Operating_modes_(ECO,_Normal,_PWR_and_EV)

Go ahead, try the buttons. They aren't there for show.
Perhaps one of those modes will work better for you than the other, but there is only one way to find out.
Best thing is to try a mode over a tankful, or a weeks driving to work and back, and then compare it with a different mode. Single trips won't reveal much of a result.

grogi

Hector Island wrote: »

Thanks Chippy01!

Actually, just reading my last reply, I mention using ECO mode, but really what I mean is that on the dash, the ECO light comes on at certain times, depending on how I'm using the pedal. But I see there's an ECO mode button, as well as an EV Mode, and PWR Mode. I never push these buttons in! Perhaps I should?

It depends on your self control... If you are nervous, going into ECO mode might help a bit.

Bigus

Keep your tyre pressures up , a lot of Prius Drivers would be getting better mpg with pressures up around 44 psi , also make sure you put on a good brand of low rolling resistance tyres when replacing. Loads of tips on priuschat.com.

grogi

Bigus wrote: »

Keep your tyre pressures up , a lot of Prius Drivers would be getting better mpg with pressures up around 44 psi , also make sure you put on a good brand of low rolling resistance tyres when replacing. Loads of tips on priuschat.com.

But that's applicable to any car - higher and low resistance tyres give same results regardless if that's diesel, hybrid, petrol or electric...

SantaCruz

Prius saves fuel in stop-start city driving. The battery is just dead weight most of the time on the motorway. This isn't secret or new knowledge to be fair.

zilog_jones

SantaCruz wrote: »

Prius saves fuel in stop-start city driving. The battery is just dead weight most of the time on the motorway. This isn't secret or new knowledge to be fair.

This isn't "knowledge", it's complete and utter nonsense. The motor generators are integral to the transmission and are always doing something, at any speed. If you want maximum power in any condition, it's both the ICE and MG2 doing work.

Chippy01 wrote: »

When that last pip flashes, it's best to fil up asap. That 50 miles can easily be cut via strong head winds, heavy weather, etc. I've heard it's not advisable to run out of fuel in a Prius

50 miles is still being fairly cautious - with a pessimistic fuel consumption of 5 l/100km you can go 180 km on 9 litres of petrol. Of course you don't want it to go completely empty, but you can go 80 km fairly safely - as long as you're in a place where you know where petrol is available, etc.

grogi

SantaCruz wrote: »

Prius saves fuel in stop-start city driving. The battery is just dead weight most of the time on the motorway. This isn't secret or new knowledge to be fair.

Not entirely. Only a person who never drove a full hybrid on a motorway would claim it is dead weight.

Battery and electric motor (there are two of them, but for simplicity) enables the engine working in much more efficient Atkinson Cycle, as opposed to Otto cycle in conventional petrol car. This alone brings a few percentages of efficiency. On top of the above, any breaking, exp. during descent. does not waste energy as much as in a non-hybrid car. This energy can be then reused when accelerating or climbing.

So while the battery treated as additional weight only takes a few % of efficiency, the overall benefit of it way outweigh the losses. Overall it would be around 10% more efficient than conventional petrol car same size.

SantaCruz

zilog_jones wrote: »

This isn't "knowledge", it's complete and utter nonsense. The motor generators are integral to the transmission and are always doing something, at any speed. If you want maximum power in any condition, it's both the ICE and MG2 doing work.

This is not nonsense. It's fact.

You don't use maximum power cruising on the motorway - you're using just the petrol engine 98% of the time.

HTH.

SantaCruz

grogi wrote: »

Not entirely. Only a person who never drove a full hybrid on a motorway would claim it is dead weight.

I do it weekly.

Can you explain briefly how the Atkinson Cycle requires the battery?

grogi

SantaCruz wrote: »

I do it weekly.

Can you explain briefly how the Atkinson Cycle requires the battery?

Ankinson Cycle engine is very efficient, but produces sensible amount of torque only in narrow range of rpms. The electric motors can produce loads of torque, so they are used to fill in where the engine lacks.

Theoretically you can build Atkinson cycle engine without electric support, but it would be undriveable.

SantaCruz

grogi wrote: »

Ankinson Cycle engine is very efficient, but produces sensible amount of torque only in narrow range of rpms. The electric motors can produce loads of torque, so they are used to fill in where the engine lacks.

Theoretically you can build Atkinson cycle engine without electric support, but it would be undriveable.

Right, but I presumed you were speaking in the context of motorway driving (for that is what we were talking about!).

On the motorway, you are cruising entirely on petrol power. If you mash the accelerator to overtake something, the electric motor will kick in for a few seconds.

grogi

SantaCruz wrote: »

Right, but I presumed you were speaking in the context of motorway driving (for that is what we were talking about!).

On the motorway, you are cruising entirely on petrol power. If you mash the accelerator to overtake something, the electric motor will kick in for a few seconds.

Sight... You might not use electric motor on the motorway (you do though, not as much as in the city), but without it you wouldn't have as effective petrol engine in the first place.