Doctor Diesel


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Hi Doc,


I have recently purchased my second Mazda6 diesel – a great car. Reading your report on the Mazda3, you cast some doubt about the reliability of the engine. In three years and 30,000 miles of mainly non-motorway driving, I have experienced no problems.


Now that this engine employs the use of AdBlue, do you think this will overcome the problems you mentioned? Using the infotainment screen, you can see the fuel economy for each mile travelled, making it easy to see when regeneration is taking place, and how often. It seems that if the engine is stopped during this process, it continues again when the engine is restarted.


Changing the subject, it seems that many cars now come with very attractive diamond-cut wheels, which are frequently scuffed. Could tyre manufacturers add a little something to provide some protection? I am sure the reduction in fuel economy is worth paying to keep the wheels perfect.


Looking ahead, can you tell me how much driving is required to restore the battery power to a hybrid vehicle. And finally, could you put the prices (basic or range) by the fleet cars so that we can compare more easily.


Great magazine, though the diesel range is steadily reducing.


Yours sincerely,

John Richardson


Hello John,


Congratulations on your new purchase. I have a huge amount of time for Mazda and its engineers. The Skyactiv engines are superb, if they are well-maintained. That’s the key. Regular maintenance not only prevents many of the problems, it also ensures an early diagnosis. In the case of the faulty injector seals, the problem is far worse if it’s undetected, and there’s more chance of this happening as the car gets older and services are missed or forgotten. I have no doubt that your engine will give you years of reliable service. Selective Catalytic Reduction (SCR) was added to the Mazda6 2.2 diesel as part of the 2018 facelift – it will certainly help with the life of the diesel particulate filter.


Moving on to diamond-cut alloy wheels, isn’t it amazing how quickly these filtered down to cars at the cheaper end of the market? Does a Dacia Duster really require diamond-cut wheels? That said, at least the sidewalls should do a good job of protecting the wheels from the kerb. There are two issues here: normal wear and tear, and damage. In the case of the former, some form of degradation over time is inevitable. Stone chips will damage the lacquer, which means water will get beneath the surface. This not only looks unsightly, but it will also spread if left unchecked. I’d advise using some wheel sealant to provide some protection. You’ll see the stuff advertised as sealant, guard, armour or wax, but they all do the same thing. Although it won’t prevent big chips, it will make the wheels easier to clean, guard against the build-up of brake dust, and ensure they last longer than wheels without any protection. As for kerbing, it’s possible to buy rim protectors, with Alloygator arguably the most famous name in the business. They’re quite expensive, but you can buy them in different colours, and a set of four is going to be cheaper than repairing four diamond-cut alloy wheels. A friend of mine looked into it recently, and the difference between the cost of repairing standard alloys and diamond-cut wheels was huge.


As for charging a hybrid’s battery, there are a number of factors at play here. You need to consider the size of the battery pack, the amount of braking involved in a journey, any settings for energy recuperation while braking, the type of journey, and the driving style. Remember, the battery pack is much smaller on a hybrid, delivering around a mile of pure-electric driving at a time. It’s therefore quicker to replenish than a plug-in hybrid battery, albeit without the option of plugging the car into the mains.


Regarding your point about prices, you’ll see that your wish is our command, and we’ve upgraded the pages as requested. Stay safe.



One Response

  1. Only thing I’ll say in relation to some of the poster’s comments is don’t buy alloygators for diamond cut wheels as the water gets in between the alloygator and the wheel ruining the finish quicker than time itself. In addition that there are some tyres the brands of which escape me but a quick look on the likes of Black Circles will tell you, that you can get tyres with rim protection. I have 19″ diamond cut wheels on my diesel Kadjar and have to be very careful as my tyres don’t have rim protection but such tyres slightly more expensive as they are but cheaper than replacing the wheel itself if they are damaged do exist.

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