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Home › Features › Doctor Diesel › Doctor Diesel

Doctor Diesel

Posted on August 30, 2019 by Steve Dawson — No Comments ↓

Weighty question

Dear Doctor

Re: Modern vehicles and their specified towing weights: Would you please explain the relationship between vehicle kerb weight and trailer gross weight? It would seem the Caravan Club’s advice of 85 per cent for trailer weight against towing vehicle weight is no longer valid in the modern vehicle manufacturers’ world. Your data for the current Skoda Octavia, for instance, shows the top specification 4×4 model with a kerb weight of 1,500kg for the car and a maximum trailer weight of 2,000kg. Surely this might be a recipe for “the tail wagging the dog?” 

Regards,

Harry Ayling

Hello Harry

Thanks for your message. I have today consulted the Diesel Car towing expert, our Editor Ian Robertson, to confirm my own thoughts, and he has advised me as follows: He recalls that, some years ago, a Daimler (Mercedes-Benz) engineer told him that the high torque figures of diesel engined towing vehicles allowed them to safely, and comfortably, tow caravans and trailers that exceed the weight of the towing vehicle involved. Evidently the manufacturers perform a series of test runs, involving things like pulling away on a specific gradient, to arrive at their maximum towing weight figures. From existing knowledge, I imagine that they would know pretty well what sort of figures to expect, even before such tests, based on the engine performance and the traction abilities of the drivetrain and wheel/tyre combination. 

With a 4×4 car like your Octavia, the superior traction would aid progress considerably in this kind of test, and this explains the higher 2,000kg rating compared with the 1,600kg for the 2WD 2.0 TDI variants. Ian feels that the Caravan Club is possibly not in touch with all of today’s cars, and the benefits of their electronic traction aids. The 85 per cent rule was set back in days when cars were less advanced, but they have stuck to the old rules. Apparently, the Caravan Club do add a caveat that “experienced” towers can go up to 100 per cent of the towing vehicle’s kerb weight, although this would still be well short of the 2,000kg Skoda rating. In a world of frequent litigation, one feels that manufacturers would not issue their figures if they were not confident of being able to back them up in court, were it to come to that. I might also add that today’s braking systems are also far superior to those of past times! I hope that you find this a satisfactory answer to your enquiry! 

Best regards, 

Doc Diesel


Damned Dirty Diesel

My friends at the Women’s Institute are scaring me and saying that I should sell my beloved diesel Fiesta, because it’s polluting the planet. It’s only 18 months old now, the latest shape, and it does exactly what I need. I get 60mpg or more out of every tank of fuel and, because I negotiated well when I bought it, I got three years’ worth of servicing thrown in for free. So, as far as I am concerned, apart from the cost of diesel and the insurance, I haven’t got to pay out for anything for another 18 months, when I will replace it with another car. My friends say that I should cut my losses now and get rid of it while it is still worth something – what do you think Doc? 

Debbie Daltry, Newport

Hmmmm. This is sadly a typical example of the effect that the media have had on diesel sales, and there’s no real justification for it, bearing in mind that your car is of Euro-6 specification, and thus suffers no discriminatory action, in terms of any charges, from the government or local authorities. Yes, emissions regulations are tightening all the time, but where’s the sense in selling a very modern, very clean diesel, that somebody else would undoubtedly be very glad to have instead of you? Would you ask a garage for an opinion on a cooking, knitting or embroidery problem? Then why take notice of other ladies who, with all due respect, not being Diesel Car readers, don’t know half as much about cars, and diesels, and emissions issues as probably you do! 

But why would you want to change it for a new car in another 18 months Debbie, let alone now? I have to tell you that you’re not getting the best out of your diesel Fiesta if you are thinking of changing it after what, maybe 25,000 to 30,000 miles at most? The engine is only just beginning to hit its best efficiency, and you would do well to keep it at least four or five years, in my humble opinion! Anyway, I do urge you to ignore the thoughts of your WI friends, and keep enjoying your diesel Fiesta – it’s one of the very best small diesels around, and there’s no logic whatsoever in changing it for anything else just now! 

Best regards,

Doc D


Green Rental

Dear Doc, 

You might be interested to know, in light of your discussion with your correspondent Bill Cargill, that the City of Aberdeen operates, in conjunction with Stagecoach and First Bus, a fleet of 10 hydrogen-powered buses (soon to expand to 20) and has established a car-sharing club with a number of hydrogen-powered cars (Toyota Mirai, I believe) available for hire by the club members. Details are available online – search “Aberdeen hydrogen vehicles” or similar for more information than I can offer. I hope you find it useful. 

Best wishes, as ever, 

Bill Lawrie

Interesting Bill. It seems like the city of Aberdeen is trying to shed its oil industry connections and present a greener image! The first thing that comes to mind, seeing that the “Co-wheels Car Club” also offers conventional (Aygo and Verso) petrol cars, hybrids (Yaris and Auris) and electric (Zoe) rental cars, why the diversification to hydrogen power is justifiable. Probably mainly because the bulk power source is there already, for the bus fleet. That sort of exercise to use resources of bulk hydrogen could well work elsewhere, of course. But did you take a look at the rental charges?

Picking just three: Hydrogen car: £50.75 per day, plus 26p/mile, Zoe: £38.50 per day, but electricity free, Auris Hybrid: £43.75 per day plus 18p/mile. Considering that, as I have pointed out before in DC, Scottish electricity is so clean, on account of the large contribution of wind and nuclear power, I would struggle to see much justification for all the various options on offer, although maybe these are not all offered at all of their rental locations?

Taking a low-cost day, when somebody covers, say, even as much as 200 miles, which I would think of as a likely maximum, the costs per mile work out, according to me, at: Hydrogen car: 51p/mile, Zoe electric: 20p/mile, Auris Hybrid: 40p/mile, Aygo Petrol: 35p/mile. So, unless you are very green, why would you hire the hydrogen car? If they did charge for the electricity on the Zoe, even at 20p/kWh, and getting a pessimistic figure of only 3 miles per kWh, it would add just £14 to the day’s costs, or 7p/mile – although the Zoe might well struggle to go 200 miles plus on a charge. But the “best buy” really would seem to be the Renault Zoe, for up to 150 miles in a day, say, at 25.66p/mile, with the free electricity. That has to be cheap motoring, if it suits your lifestyle! 

How about you Bill, if you lived in Aberdeen? Hope my figures are correct! 

Regards,

Doc


A premium question

Just a quick enquiry Doctor. The world of car insurance seems to be getting more complicated, and unfair. A lady friend of mine had a minor collision recently, not long before her insurance renewal came up. On reporting the incident, she found that her premium had increased significantly, and she followed this up by enquiring exactly why. She was told that it was the result of her minor collision, which was one of those that was left rather open, and probably settled on the traditional “knock for knock” basis. The whole thing seemed like history to her and, in fact, for her car, all that was involved was a repair to an alloy wheel that she paid for herself, precisely in order to protect her no claims bonus. There was no investigation, it appeared, as to whether one party or the other was to blame, even though she was quite sure in her mind that it was the other person. This seems a fairly typical sort of situation, but the end result was around a 30 per cent increase in her premium, irrespective of her “no claims protection” for which she pays a small extra premium. 

D Bullard

Unfortunately, the way things work today, any accident you have, whether in your car, a rented car or one you are borrowing, can, and often does, lead to an impact on your own car insurance premium. That is because insurers, having asked the question “Have you had any accident or claim in the past five years?” include your answer to this as part of their premium assessment.

Therefore, some (many!) insurers might well see fit to increase your basic premium as a result of having taken into account your wider driving record, the cost of the claim, and other factors. It is not your friend’s no claims bonus that has been affected, but the basic premium. People do not always realise this sort of thing can happen when they pay these extra premiums for protection of their no claims bonus. The insurer argument is effectively, it seems, that people who are involved in accidents, be it their own fault or not, are then statistically more likely to be involved in another accident, and therefore the premium must rise!

Throwing in my pennyworth, I suppose it is arguable that good drivers are better at avoiding all types of accidents, their fault or not, and it’s an excellent argument for “defensive driving” where you must assume at all times that other drivers are likely to do unpredictable things that can end up causing minor collisions. I hope this helps you understand the logic of your friend’s situation, and that you can pass this on to her. 

Best regards,

Doc Diesel


Polo Problem

I am wondering if the esteemed Doctor might be able to help me with a problem? My Polo has only covered some 14,000 miles of fairly gentle motoring, over a period of just over three years, and my garage reported (in the “advisory” notes) that my front and rear brake discs and pads would need renewing in the next few thousand miles, mainly on account of surface corrosion of the discs. As I say, I drive at quite modest speeds and I cannot understand why the discs should need replacing, as well as the pads, seemingly at a cost in excess of £300. Please advise. 

Tom Geraldson

Well, this is not an uncommon situation Tom, and I think that, amazingly possibly to you, your modest driving habits are at the root of the problem. Some years ago (back in 1999, believe it or not!), asbestos brake pads and discs were banned, and replaced by alternative materials which also demanded a change in the material of the discs themselves, and these are subject to corrosion, more than wear, with most cars. The less that you use the brakes, the more corrosion can get a grip on the pads, and if you were shown the state of them you would probably have to agree that they were needing replacement. With the way that braking effort is apportioned between front and rear, according to the weight on each axle, if you rarely travel four-up, or with much weight in the boot, the rear brakes in particular will rarely be called on to do much work, and accordingly they will corrode faster than they will wear, believe it or not. So I’m afraid that you are probably going to have to bite the bullet and get them replaced. 

I might add that, whilst I often advise shopping around for garage work, I would probably not in this example advise going to a cheaper garage, where the job might cost you a bit less, as cheaper quality discs that they might fit are often more prone to corrosion than better quality ones that your Volkswagen garage should supply. Particularly on wet days, you might help arrest the corrosion by making a few firm brake applications as you approach home, ready to park up. It should help dry out the pads and discs and reduce the corrosion you might have if the brakes are saturated, and a short application of the handbrake as you slow down would also disperse some of the water in the rear brakes. Sorry this is of little consolation to you Tom, but that’s the way it is! 

Best regards,

Doc


Bigger is better?

Dear Doctor, I have been thinking of changing cars soon, and I am probably looking at a SEAT Leon, Skoda Octavia, or Volkswagen Golf, and I want to stay with an automatic, like my present Octavia 2.0 TDI, which has served me very well, but is now approaching 65,000 miles. But, as I have probably slowed down with the passing of the years, I am now wondering whether to switch to a 1.6TDI, in view of the likely better fuel economy, and because I don’t feel that I really need the extra performance of the added 34bhp of the 2.0 TDI. I am also thinking of going automatic, with the VW DSG transmission. Your opinion on this proposed switch would be much appreciated, and any comments as to whether you would steer me towards any particular model of the three that I am considering would also be very useful. Hope you can help! 

Colin Richards, Wolverhampton

P.S. You can see that I am determined to stick with diesel power!

Interesting thoughts Colin. If I might be so bold, it would seem that cost is not too critical to you, and you would get most of the extra cost for an Octavia 2.0TDI DSG over a 1.6TDI DSG back when you eventually traded the car in. But I would definitely stick with the 2.0 TDI if you are thinking of the DSG transmission, for one particular reason, and that is that the 7-speed wet clutch DSG on the 2.0 TDI is a far better and more robust unit than the dry clutch one that comes with the 1.6 TDI, which can suffer from reliability problems. Added to that, the fuel economy penalty with the 2.0 TDI is pretty minimal – maybe 3 to 4mpg maximum. 

But do have a decent test drive with a DSG transmission model before you jump in at the deep end – it would be a very bad move to buy blind. If there’s no DSG test car that you can have for a few hours, if possible, for a really good test drive, I think you would be best looking at the current 2.0 TDI 150 engine, particularly if you go for a DSG automatic, but you should be very aware that a new model Octavia is pretty imminent, as is a new Golf, with a new SEAT Leon due early next year. Now this means it might be a smart time to pick up a bargain, unless you’re really dying to have all the next generation of driver assistance technology that will undoubtedly come with these new models. So you need to keep a good eye on the marketplace for well-priced Golf and Octavia offers over the next month or two, and you might pick up something at a really good discount. 

As a happy Octavia owner, particularly if the Skoda dealer that you use has treated you well, I would also tend to stay with Skoda, rather than switch marques, and of course you might well find a Golf or a Leon rather cramped after your spacious Octavia.

Hope this helps with your thinking. Do come back to me if you have any further thoughts. Best regards, and good luck with the buying exercise. It’s all quite exciting! 

Doc Diesel

‹ Volkswagen readies new eighth-generation Golf
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Tagged with: Caravan, Daimler, Fiesta, Polo, Skoda Octavia, Stagecoach, Volkswagen
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