Love Your Prius!

[Carltona123]

Hi guys

So I had to move my daughter from Solihull to Newcastle University. A container was out of the question on grounds of price so it had to be done by car. Would all of her stuff and four people fit into my 57 plate Prius? Didn't want to risk it so agreed a rental on a Volvo V70 estate. Turns out he gave me a V60 which, when I got it home, turned out to be no bigger than the Prius. Load space was rubbish - really high boot floor and dead narrow; I would go so far as to say the Prius had a bigger capacity. Anyway I thought if I was going to overload anyone's car it wasn't going to be mine so I shoehorned the lot in.

It was a diesel auto with stop start and 3k on the clock. I set the cruise control to 73 and headed for the Toon. Arrived 3 1/4 hours later. Computer showed 49 mpg - hardly anything to write home about. Around town I was lucky to get 30 mpg and the stop start was really irritating. So happy to hand it back and get into my Prius. On the seven mile run back from the depot I got 75 mpg.

Two weeks later did the same run in the Prius; same weather etc and again a big load. Did it in an identical time for an indicated 53 mpg (which I know is on the optimistic side, but then so too may be the Volvo's). Plus diesel is 6p a litre more expensive.

Toyota 1-0 Volvo

[Surv1v0r]

75 mpg sounds pretty damned good - 53 mpg less so. Any idea why there was such a big variation?

[Carltona123]

Oh that 75 mpg was starting off with a pretty full Battery, and it was a nice warm afternoon. It always does better around town - that's why the motorway mpg's can sometimes come as a bit of a disappointment. I was just heartened that my 6 year old Toyota could give a state-of-the-art diesel equivalent a run for its money.

[r04drunner1]

Love it!

My Dad has a V70, so I know you can get loads into them. More than a Prius could handle, to be fair.

But I am not surprised the Prius did better than a V60 diesel in MPG. Factor in the zero RFL, relative cost of diesel versus unleaded and we have a clear winner on that occasion.

[cootuk]

The old Audi diesel engine that Volvo used was excellent for fuel economy, but there do appear to be a lot of complaints over the new D5 ...mid 30-40s for a diesel is atrocious.

[Carltona123]

I actually had my car serviced last week (by Mr T) and had a very interesting chat with one of the senior technicians. I was saying how much I liked the Gen 2 and how I intended to look after it and keep it long term. I used to be a big diesel fan but they don't seem to be as solid and reliable as they used to be. He agreed and pointed me towards a Rav 4 in the workshop - okay it was a 55 plate but it had only done 100k and was in for a new turbo, flywheel and clutch...I asked him about reliability on the Priuses and he said he'd been with Toyota since they first came out. Early concerns about the traction Battery have proved completely unfounded, and even when and if it needs changing it would come in at way way less than putting the Rav right was going to cost. He said the only thing to keep an eye on is the 12v Battery - at six years old mine might need changing soon.

[Cyker]

75 mpg sounds pretty damned good - 53 mpg less so. Any idea why there was such a big variation?

Well it was empty vs fully loaded so you tend to get pretty large variances on that with petrol engines, esp. low-torque ones, although I expected the leccy bit of the HSD to offset that more in this case.

Diesels tend to be better for that; I find my Yaris D4D has a much smaller variation loaded vs unloaded (except when there are hills involved ). It think it's mainly because with diesels you can still pull in the same gear you'd normally be in, but in petrol you need to stick to the lower gears for longer.

Modern diesel tech has the potential to do 100+mpg but they're been completely screwed by all these emissions regs forcing companies to fit devices that make them less reliable and less efficient.

If I got a modern Yaris, I'd probably pick up the HSD and not the D4D for that reason, but you'd have to pry my Mk1 D4D (With FIVE DOORS!!! ) out of my cold dead hands first!

(It's soooo nice and fun to driiiive :D )

[timberwolf]

Let me try to explain what is going on with an example.

a. A Prius is parked at the bottom of a hill. Average MPG meter is reset.

b. The Prius accelerates up the hill at 30 mph - accelerating up the hill takes effort. Computer indicates 25 MPG!

c. The Prius reaches the top of the hill and car is now on a level plateau (a mini Table Top mountain?), the driver eases off the accelerator, the effort required to keep the momentum going is much less on level ground, lets pretend the computer shows 50 MPG (it will normally be more if the driver feathers the accelerator).

d. The car reaches the down slope of the hill, the driver eases right off the accelerator, the computer indicates 99 MPG (it could be higher but the computer only displays two digit MPG).

For our fictional journey, lets say the up hill climb with the rubbish MPG is neatly compensated for by the downhill stretch, and so the overall figure displayed by the computer at the end of the journey is 50 MPG.

If we go back to the start and repeat the journey but the driver resets their computer displayed mpg for a second time (during that journey) when they reached the top of the hill and then looked at their displayed MPG when the car reached the bottom of the hill it would read a much higher than 50 MPG!!

You should always be wary of any owner that reports MPG for a single trip or part of a trip using the on-board MPG displays especially if the owners resets the MPG counter during a trip.

I believe the only fair and meaningful way to measure mpg is to calculate it using the number of litres pumped from a petrol pump and the distance travelled and even that has to be averaged over many fill-ups to smooth out the variations in filling the tank.

I've kept the example simple (because my brain would hurt) - to make it more realistic, we would also have to consider many factors such as (but this isn't a complete list):-

the warm-up phases of the engine and emission systems (anti-pollution including Catalytic converters),

the ambient temperature (outside air),

cabin temperature setting,

drag on the car (speed the car is being driven),

the weather - e.g. wind direction, rain, etc.

The cold weather can be significant, and it will surprise many new owners - I like to think of it as the Hybrid winter blues!