New PB! Finally Above 70mpg(US)
 

I just pumped 27.36L into my 2014 Toyota Aqua (JDM Prius C) after 858.5km on the odometer's trip meter. This equates to 3.19L/100km (73.78mpg(US)). I achieved this by adjusting my driving habits, keeping an eye on my battery charge and engine stats on the HybridAssistant phone app, and tyres inflated slightly above the door jamb recommendation.

As New Zealand goes into autumn and then winter, this is the best fuel economy I am expecting to get. I am considering grille blocking if the temperatures are such that the engine struggles to keep itself above its miminum 40°C during my relatively short 14km commutes. Already a couple of times this week the weather was cold enough that the engine turned itself on whilst I was waiting at traffic lights because my engine-off coast beforehand had cooled the engine. I had to manually turn it off with my car's "EV Mode" button, deactivating EV mode only when it was time to drive off.

Nice!

You might consider pre warming the engine if its short commutes from/to the same places.

Does anyone make a plugable element with a pump and probably an alternative to your stock thermostat?
Something you can simply splice into your cooling system?
(And remove the stock thermostat while you're there)

Thanks for the advice and suggestions! I'm not certain about the legalities of modifying my car's thermostat here in New Zealand. Beyond a certain threshold, any modifications requires an additional low volume vehicle (LVV) certification and additional inspections atop the annual Warrant of Fitness (WoF) inspections. However, regarding pre warming, I have had my eye on installing an engine block heater. As far as I can tell, this does not require additional certifications and inspections.

Great work! I've been able to manage 70+ on many trips but my lifetime is still in the low 60s, due to cold winters. How healthy is your hybrid battery?

Glad you like the idea. :)

If the pre heater is a element and pump combo doodat that splices into say the upper hose; then it can simply be removed and an original hose fitted for inspections.

Thermostats are simple melting wax actuated things as explained here:
https://savree.com/en/encyclopedia/engine-thermostat

They simply fit in a housing on the engine side of the top radiator hose and are simple to remove/replace.
In fact in Equatorial Africa thermostats only last until they give trouble or the car runs hot.
They are then removed/omitted and tossed far and you get a dirty look for not having removed it ages ago! :)
(Ye they don't understand or care for the engine longevity and economy advantages)

The only reason one would want to move the thermostat is that the wax bulb is on the hot/engine side where its difficult to fit a heating element close-by.

Could you post links the the pre heater you have your eye on?
There are a couple of water heaters (with pumps) on the market I see.
They seem to fit into the thinner pipes going to/from the car interior heater radiator in the dashboard.
I don't know that they do much besides make the interior heater work instantly..? It all depends on the cooling circuit for your particular car.

Also; if they are car battery powered rather than wall plugged they just move the load to the car's alternator after startup, negating any economy advantages.

I see you also get fuel powered heaters! WhatTH!??
No time for that research atm.

Edit/Update: (I was just too curious! :) )
It seems that the heating circuit for the interior heater-core is on the engine/hot side and bypasses the thermostat/s.
This makes sense as you want your customer's car heater to start working asap!

You can see a whole lot of cooling circuit diagrams here:
https://www.google.com/search?q=car+...M&vssid=mosaic

The hot water for the heater normally comes from the area close to the thermostat.
So lets say one fitted something like this:
https://www.amazon.de/-/en/Auxiliary.../dp/B0BJZZYCWB
There will be some flow of hot water over the thermostat.
So if the pre-heater, which has it's own thermostat switch for the element, (and pump) heats the water to above the opening temperature of the main thermostat; then the main thermostat will open.

However I don't 'see' much flow through the main radiator due to the small pump and flow (if any) will be in the opposite direction to normal.

Be that as it may, there will still be more heat in the cooling system pre startup which should help considerably.

NB that all this revolves around the interior heater being ON:
If not; the water valve in the interior heater's water circuit will be closed and the small pump cavitating. ie: No flow.


I would say that a system like this would be complimentary to a sump heater as there is no water cooling of engine sumps. That's where the oil lies and it too can be heated pre startup.
In fact; it should be pre circulated/pressurized before startup if you want your engine to last..

Not sure as to the health of my hybrid battery, but it is the original one since it was imported from Japan. It would be 10 years old this year. It had a couple of instances recently where the state of charge plummeted from full to empty over a few seconds whilst not doing anything. Priuschat said it may be a sign the battery's bus bars need cleaning of corrosion. I started shopping locally around for quotes to get the hybrid system inspected and cleaned.

This June to August will be my first winter since starting to practice hypermiling driving techniques. Due to colder ambient air, it already takes a few more seconds for the engine and hybrid system to reach Stage 2 at 40°C to enable EV mode. Normally it reaches this stage before I exit my 30km/h housing development neighbourhood onto the 60km/h suburban main road that takes me to work. It could be worse. I park inside my garage, unlike many people in NZ, so the engine already warms up from double-digits Celsius. Grille blocking with a length of hot water pipe insulation has definitely helped.