Keep It Clean!

[JuicyJaffa]

Having an '08 Prius, I'm always interested in how to get better fuel economy. I over inflate the tyres a little to help reduce rolling resistance, drive conservatively pretty much every where and rarely use the air con. Typically I get 54-56mpg, not great compared to the claimed figures, but reading around, it's about average.

The other day, my Prius had to go in for its first service. I thought that there may be some tricks that I haven't read about that may help me get better fuel economy that the service department at my local Toyota dealer might be able to impart, so when booking the car in and having been asked if there were any problems, I mentioned that I was experiencing poor fuel economy compared to that which I had originally got when I first had the car (I quoted that I originally got about 60mpg and was now getting low 50's - little white lie I know, but I was fishing for an improvement). I mentioned that I would appreciate it if things could be checked and let me know what problems there might be or indeed how to get better economy by changing my driving style.

When collecting the car after the service I asked if anything was found that might be affecting the economy or if there were any tips to gain an improvement. The nice lady said (and I'll quote as close as I can):

"Your tyre pressures were too high and have been reduced to the pressures recommended by Toyota, the 'Engine Computer' has been reset and you need to polish your car more often. If you stick with the correct pressures in your tyres and don't over inflate them, polish your car more regularly and considering the reset, you should experience a SIGNIFICANT improvement in your fuel economy!"

I nearly fell off the chair I was sitting on (but held the laughter)!

I mentioned the rolling resistance theory but had it dismissed as "The technician wouldn't agree!". I admitted that the car was dirty when it came in but in general I kept it clean (the offer of a free wash in the service prompted me to neglect my weekly wash that week and living in the countryside does make for a dirty car!). In confirmation I asked "So if I keep the tyre pressures standard and more specifically, POLISH THE CAR MORE OFTEN, I'll get better economy by 10-20% then?" the answer came as an emphatic "Yes.".

So since the service the car has been clean and the tyres have been at the standard pressures, and over the 250ish miles since the service and driving in my standard way, economy is down to 50-52mpg. I think I'll pump the tyres up again!

Thanks Ipswich Toyota - you just gotta laugh eh!

[Chris Dance]

Juicy Jaffa. That is just a great story.

My car is rarely dirty as being retired I can keep it immaculate and I only use recommended tyre pressures. I drive as economically as I can and at the moment I am getting 54.9 to the gallon. Last summer I got 57 to the gallon which is the best I have ever achieved. My dealer informed me that what I am getting is about right for normal motoring. I did meet a chap who said he got a regular 60MPG???

Oh well must use more elbow grease when I polish the car in future, you never know I may get another half mile per gallon.!!!

[benw123]

That's priceless. I absolutely minted my T-Spirit over the weekend - Autoglym polish, glass cleaner and Meguiars tyre shine - and saw no improvement on my commute this morning. Bang on 55mpg with over-inflated tyres and A/C running.

It's going in for an MoT tomorrow so I might ask for similar advice.

[fuel miser]

I came across this site with a few Prius owner reviews, and an extensive piece written by "Richard Stevenson from Seven Sisters" who is a salesman for Toyota. I was interested in his comments on the Prius dirive shafts, which he says generally fail at 60k, and rusting of the brake discs (he didn't mention rusting of the alloy wheels which is a common problem, they all had to be replaced on mine). Does anyone agree with him?

http://www.greencarsite.co.uk/GREENCARS/To...rius-Hybrid.htm

[timberwolf]

What does he mean by drive shaft? If he means either a CV joint or wheel bearing then no I've not read about many failures.

Rusting of discs I've heard of, but I prefer an alternate remedy of finding a quiet spot with no one behind me, driving at 30 mph, putting the car in neutral and then applying the brakes to slow down.

[benw123]

I've not heard about driveshaft failures either, but I do accept that as a salesman on the front line, so to speak, he may well have seen such failures.

However, I've just posted my own review of my Prius which includes an opinion that definitely differs from saleman Richard, and that is why private owners don't sell their cars back into the dealer network. This is because we want to achieve a sales figure that roughly resembles the retail value, not something that's thousands less.

[JuicyJaffa]

Right...getting back to the original subject and as a follow up...

Since my original post, I've now completed 400 miles on the recommended tyre pressures (35 psi front 33 psi rear) using my normal 'economy' driving style (conservative, no A/C etc.) and driving my normal routes, and my Prius has averaged 52.2 mpg.

So today out of interest, I increased the pressures to 40 psi front and 38 psi rear (before the service I used to use 44 psi front and 42 psi rear - read from a recommendation on a web site somewhere I can't find or remember) and though it isn't a very long journey (just under 10 miles) and it includes a cold start, country lanes, dual carriage way, and traversing a town center I averaged 63.0 mpg. I drove as usual, I got to my destination with a 'green' Battery (didn't use 'EV' mode at all!).

I don't believe for a moment that it'll stay that high, but can tyre pressures really make that much difference?

[Red Yaris 54]

but can tyre pressures really make that much difference?

Tyres inflated significantly above the recommended pressures will wear faster in the centre of the tread and can lead to shorter tyre life.

The cost in replacing tyres earlier than normal might just outweigh the savings made on better fuel economy

[GreenJuice]

but can tyre pressures really make that much difference?

Tyres inflated significantly above the recommended pressures will wear faster in the centre of the tread and can lead to shorter tyre life.

The cost in replacing tyres earlier than normal might just outweigh the savings made on better fuel economy

There is much debate on these points in the priuschat.com website. Some have provided evidence that the recommended Prius pressures of 35/33 result in wear on the outside edges of the tyres, implying that they are on the low side and aimed at comfort. The Prius hypermiling community appear to have evidence to support what you have found yourself, that fuel economy noticeably improves with increasing tyre pressures, and continue to rise even through to well above the recommended limit. An extreme example you may have heard of is the Marathon Run http://priuschat.com/forums/prius-main-for...rathon-run.html where such hypermilers achieved 1397 miles on a single tank of petrol (averaging 131 mpg) in a stock 2004 Prius. I believe they used tyre pressures of 60 psi. I believe the cold sidewall pressure rating of our Bridgestone Turanzas is 44 psi. Red Yaris 54's cautionary point and potential risks of reduced traction deserve due consideration.

[fuel miser]

Well I have mine inflated to 160psi. The only downside I find with this practise is that one has to stop approximately every 230 miles in order to drain off a couple of gallons of fuel.

[JuicyJaffa]

Well I have mine inflated to 160psi. The only downside I find with this practise is that one has to stop approximately every 230 miles in order to drain off a couple of gallons of fuel.

LOL :D

Maybe with the 160psi tyres and a slightly bigger Battery and a cable from under the back seat you could stop every five miles or so, plug into the nearest domestic power outlet and feed electricity back to the grid! Crikey, if we all did it we could power a small town...where's my foot pump. :D :D

BTW, home from work and I'm still registering 62.2mpg...go figure!?!

[hertsnminds]

Some of the measures described to get satisfactory mpg do sound extreme and changing tyre pressures will effect the cars handling (and maybe an insurance claim). If you NEVER use the A/C as you want to save some fuel then you would probably be better off removing all of the components of the A/C system, I would imagine the weight saving would increase mpg.

Examples of where you will see tyre pressure having an effect on how a re car performs are: any F1 race, Top Gear (the episode on the Salt Flats), getting a vehicle across a muddy field. All non road standard situations but they illustrate the point.

I would ask the dealer if putting tape over all of the panel seams will help with mpg (as it should reduce the drag).

IMHO the Prius is not the most economical car on the market. It's USP is the amount of emissions it produces (or doesn't produce).

[GreenJuice]

BTW, home from work and I'm still registering 62.2mpg...go figure!?!

...and I'm sure for most, fuel economy probably wasn't the main reason for choosing a 5 seater petrol hybrid. But there is something about the Pruis that makes watching it more addictive than other cars I have driven. It might be partly the information display, but also the larger numbers and a sense of immediate 'reward' for 'good behaviour' (bit pervy, I know!)

However, its also worth remembering that the mpg scale is not linear. Going from 52 mpg to 62 mpg does not give the same fuel saving as going from 25 mpg to 35 mpg (its actually closer to going from 25 to 30 mpg). So although the figures are higher, the returns actually diminish the higher you go. The alternative measure of L/100km is a better scale for linear comparisons of fuel economy.