IS300h carbon monoxide emission figures from Which? magazine

[Thackeray]

For a long time I’ve been puzzled by the Which? magazine review of the IS 300h. In their initial report they made it a Best Buy but a few months later downgraded it. Its website version of the review currently says: “Best Buy award removed. It's a very good car, but we found the Lexus IS emits so much CO (carbon monoxide) in our tests, that it would fail to meet any EU emissions limits set this century. As such, we cannot possibly recommend it.”

Despite this negative review, there were lots of things I liked about the car, plus some ratings that sounded impressive:

• Best in class for 2013 NCAP safety
• World’s most efficient production petrol engine when launched, at 38.5%. (It was overtaken by a Honda six months later.)
• Routinely at top of reliability ratings.

I was also doubtful about the Which? mpg figures. Their claim of 97 mpg around town was obviously nonsense and the motorway figure of 34 mpg looked doubtful too. They say their tests are performed in a laboratory but they don’t give enough detail to tell how they get to these extreme figures. I thought if the carbon monoxide figures are based on the same testing, they’re just as likely to be wrong. So I went ahead and bought an IS300h.

I’ve searched in the past for some other independent CO test reports and couldn’t find any. Until today.

But first, what is Which? claiming? They say it wouldn’t meet EU carbon monoxide emission limits set this century. I take this to mean Euro 4 in January 2005. (There was Euro 3 in January 2000 but that was the last year of last century.) The limit for petrol cars under Euro 4 is 1 gram per kilometre (g/km) of CO.  So they’re saying the IS300h emits more than 1 g/km.

For a long time I had no way of knowing if that was true or not. But at last I’ve found a website that shows real-world emissions test results. It’s called EQUA Index and they test cars by driving them around real roads monitoring the emissions from the exhaust pipe on a three and a half hour run. They give the IS300h their top rating of A++. This represents a band from zero to 0.125 g/km of carbon monoxide. (Their result is for the 2017 model but I don’t think there are any significant differences to the engine from the 2013 model. Please correct me if I’m wrong.)

By contrast, Which? says CO emissions are more than eight times this figure. 

I know nothing about EQUA; I’ve only just come across it. But I’m more inclined to believe that real-world testing on roads will give a more accurate figure than a short test in a laboratory.

[Guest]

Carbon monoxide is taken care of by the cat making into carbon dioxide. Something that happens naturally anyway but it removes monoxide from the local area. Ie populated area.

Only works after cat is warmed up though.

Without seeing the paper of their test method it would be hard to know how they arrived at this result. Testing 1 single car isn't very scientific either.

Sent from my STV100-4 using Tapatalk

[ColinBarber]

Which? test using a more real world simulation than official tests and have found that many Toyota hybrids, including the IS, emit considerably more than Euro specs but because the test is harder they aren't claiming the vehicles aren't meeting the standard.

A lab is better than on the road because you have much better control over the environment. Wind, rain, traffic etc. would all affect the results.

[Thackeray]

13 hours ago, ColinBarber said:

A lab is better than on the road because you have much better control over the environment

It's true that a lab gives you easier control over variables. But the test is only ever an attempted simulation of real-world conditions. If it's a badly designed test the results will bear no relation to the real world. This is the situation VW got themselves into. They designed cars to do well in the test. But as it turned out the cars did badly when tested on the road.

Which? may have done a good job in improving on the design of the official lab test for conventional cars. But it's obvious that their test gives results that are wildly inaccurate for hybrid cars. They say the Prius does 166 mpg around town. I would be very surprised if any taxi driver driving a Prius 10 hours a day could get fuel consumption anywhere near this figure. In real world use, the best fuel consumption of the 2,600 Priuses on spritmonitor.de is 88 mpg. Average is around 54 mpg. The Which? test gets nowhere near to simulating these real world figures.

Since the mpg figures are so clearly wrong, I'd be inclined to suspect that emissions data in the simulation will be inaccurate too.

I expect they'll come up with a better designed test for hybrids in the future.

[Guest]

The effect of Hybrids on the made up "cycle" is similar to stop start tech. It means the vehicle can have it's engine not running for a greater period of time (calculated) than in real life.

The tax system is completely broken - the easy way to do it is to add the tax into the price of fuel - this drives real world change - but they are too cowardly to do it.

There is also an imbalanced war against CO2 - Methane is 10x as powerful and we create almost the same amount of it as CO2 - but because half the methane comes from agriculture (meat/dairy industry) it seems they just prefer not to talk about it.

I guess it's easier to get people to change car than diet?

It's a very interesting subject but one that's difficult to tackle on a forum. I'm not sure Which? are adding anything useful to be honest.

[/rant] 

[Ala Larj]

1 hour ago, Comedian said:

half the methane comes from agriculture (meat/dairy industry)

My wife thinks the other half comes from me!

[ColinBarber]

9 hours ago, Thackeray said:

Which? may have done a good job in improving on the design of the official lab test for conventional cars. But it's obvious that their test gives results that are wildly inaccurate for hybrid cars. They say the Prius does 166 mpg around town. I would be very surprised if any taxi driver driving a Prius 10 hours a day could get fuel consumption anywhere near this figure. In real world use, the best fuel consumption of the 2,600 Priuses on spritmonitor.de is 88 mpg. Average is around 54 mpg. The Which? test gets nowhere near to simulating these real world figures.

Since the mpg figures are so clearly wrong, I'd be inclined to suspect that emissions data in the simulation will be inaccurate too.

I expect they'll come up with a better designed test for hybrids in the future.

I'd suggest that Which?'s urban test is too short. Clearly the 166 mpg was performed almost entirely on Battery, it would need to be longer so more than a single Battery cycle is needed. I've managed 120 mpg in my wife's Prius on a 2.5 mile journey, but if I repeated it a couple of times then it would average down to around 75 mpg.

I therefore would understand a low CO reading, if it ran mainly in EV mode, but I fail to see how a high reading could be obtained in error. Clearly they measured the amount of CO being produced and it was well over the expected limit.

[Thackeray]

13 hours ago, ColinBarber said:

I'd suggest that Which?'s urban test is too short.

That looks very likely. There's a youtube video showing what the test involves and it highlights how short and slow the test is. After looking at the video it's easy to see how a hybrid could spend much of the test running on Battery, giving high mpg figures. 

The same test, which starts with the engine cold, could also give high carbon monoxide emissions. The video shows that some of the test is spent with the car stationary and the engine idling (if it's a conventional car). A hybrid car would probably stop the engine during these stops. As Comedian pointed out above, the catalytic converter needs to be warmed up before it starts removing carbon monoxide from the exhaust gases. But if the engine keeps stopping during the test, the cat won't warm up as quickly as in a conventional car. So the same test, being so short, could show unrealistic figures of both low fuel consumption (high mpg) and high CO emissions.

I've now checked and found that Which? has recently updated its test explanation page to describe the new test regime that's due to be introduced soon. It's interesting to see that road testing is going to be introduced to improve the emissions data. I expect that was prompted by the VW saga.

[Thackeray]

It's interesting to see that the Which? magazine in its latest annual car review gives the IS300h the top score in its class. But they continue to say it had high carbon monoxide emissions based on the test they did in June 2013. I'm still inclined to think this result from six years ago must be suspect - their mpg figures for urban and motorway use are clearly nonsense, You would think that after so many years they would publish how they achieved the figures in 2013 or at least retest in order to compare with the very different EQUA Index figure.