milage drop by over 20%

If my quick google search is correct, then the Nokia Hakka Winter tyre is still a low rolling resistance tyre. If you have changed these to a non llr then you will see your fuel economy dive.

Your findings all indicate to the new tyres. There are many threads on here about this issue. I had the same findings as you when the non llr version of tyres were put on my car. When these were eventually taken off the fuel economy went right back up to where it once was. I struggled to get 45 mpg US when I used to get 62 mpg US with ease and got again once llr's were put back on.

Not sure what your solution is? Can you put the Michelins on another car or sell or just make do?

 

Part of the problem is the lack of an established pattern of mpg. You have only had the car for 4 weeks. That does not provide many data points! Regardless, I bet your problem is with the tires. New tires will always drop your mpg compared to a similar worn LRR tire. If you replace a LRR tire with a non-LRR tire or a marginal one then the drop will be even higher. Maybe you could list the exact tire you chose. Michelin Primacy what?

 

I thought you worked in the UK Grumpy or are you buying your fuel in the US because it's cheaper.

 

lol it just makes it clearer to quote US gallons and US mpg's on an American forum. Got bored explaining the difference so often

 

(hope my english is understandable)

Similar findings here when changing from winter tyres to summer ones. (10% climb in consumption).
Same thing in my former car VW passat.

Little google and 20 year old belief turn to rubbish.

I've allways believed that winter tyres roll heavier but it's the other way round.
I'm talking about real winter tyres. Not these M+S winter tyres and those summer tyres like friction tyres they use in central Europe.

At the end of this linked page you can see difference between studless winter tire and summer tire.

nokiantyres.com/tyres-of-the-future

I guess we only notice this at spring and fall because then we drive both winter and summer tyres in similar weather conditions.

Those studless Nokian you have are one of the best rolling tyres money can buy.

In my experience the differenses in rolling between winter nad summer tyres are greater than between two summer tire.

Mikko

 

Hi
I have prius 2007 T4 its been really fine until last month i have always achieve 53mpg in and around London but suddenly it started running sluggish, i took it to Toyota and they recommended service which i did at the cost of 249 pound but this did not resolve problem engine was still rough and mpg dropped to 38mpg. Even i added fuel cleaner as well but no luck, now thats where the fun start one morning it refuses to start like no lights on dash i called AA all they did was checked battery and jump started car as per AA battery had 12.01 V and its fine but as per my research 12v battery must have minimum 12.8v to run prius at optimum. I replaced the battery just standard bosh s4 155 type cost 46 pound and waoo its like brand new car all sluggish gone and my 53mpg has came back and actually i see more time to time, so 12v battery plays very important role in mpg if your is 4 year old just dump it its a DIY job

 

Hi Ansur, welcome to the forum. Yeah the 12v causes all sorts of issues when it fails. People assume it will fail in a similar way to any other 12v in a car but as it doesnt start the car it is hard to tell when it starts to go bad. Usually its around the 4 - 5 year mark or 70,000 to 80,000 miles.

The 12v the AA were checking was probably coming from the inverter which charges the 12v in a similar way to the alternator on a traditional car. As the engine doesn't need to be running, people, the AA included, believe they're measuring the battery when they're just measuring the charge.

The failing 12v is a very common issue which doesn't seem to have been picked up by UK Toyota dealers, but if you have any friends who have a Prius let them know as it'll save them a whole load of hassle.

Whilst you're here, another good improvement to your car is to use low rolling resistance tyres when you next get some - they're not that much extra and really do work in saving money. Also, make sure your tyre pressures are spot on - 2 psi down and it'll seriously affect your mpg's.

 

So I should see my mpg go up as the factory tires wear in? I have 1200 miles on the Yokohama Avid 33's that came on the Prius. Average 52 mpg.

Planning on Nokian WG's for the winter and skiing (December-April). Nokian says they are low rolling resistance tires. Hope to keep the car to 50 mpg.

 

Yes. Rolling resistance is reduced as tires wear down. So mpg is usually increased over te lifetime of a tire. When you replace the tire you start all over again.

The Nokians are an excellent winter tire. In fact, their Hakkapeliita tire (snow tire) is their lowest rolling resistance tire. Too bad summer temps would destroy them quickly.

 

I second the Nokians for winter. We even had those on a 96' Miata and that thing went through the snow like gang busters! Summer for the Prius.. i go with Hankooks from tire easy, they are a great value.

 

I have 321k+ miles on my '06. I have lost count, but I think it is on it's 4th set of tires.

MPG has always been affected most by the weather. Temperature of the air, whether it is raining or not will affect mpg too.

2nd most reason? Maybe tires. Not sure. Mpg does creep up a bit as I wear the tread off of the tires, and then drops when I put new tires back on, then creeps up as I wear that tread off and so on. Some tires have done better with mpg than others. My priority has always been wet road handling, not mpg. The tires I have on there now, are a little wider than standard, because there was no tire in the size I needed at the time i bought, and so mileage took a little hit on that. So right now I am averageing about 47 to 49 mph after the first 1000 miles of not pressing the reset button on the MFD.