Author Topic: Mileage to warrant a diesel?  (Read 1583 times)

Steve McF

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Mileage to warrant a diesel?
« on: 11 October 2023, 12:45:21 PM »
Hi all, here's a general question. How many miles and what sort of driving do you need to do to make having a diesel worthwhile? I am thinking particularly cars with DPFs etc.

If I drive to work on the nearby A46 (dual carriageway) and M40, I probably do about 10 or 11 miles. So if I go that route and back, 5 days a week, it would be that distance each way at around 50 - 70mph.

Would the car suffer DPF issues with regular journeys like this?

TomPaine

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Re: Mileage to warrant a diesel?
« Reply #1 on: 11 October 2023, 09:47:24 PM »
The HonestJohn response to this question has always been a minimum 15k miles pa -

https://www.honestjohn.co.uk/askhj/answer/157193/i-drive-8-000-miles-per-year-mostly-around-town-should-i-buy-a-diesel-

carrera

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Re: Mileage to warrant a diesel?
« Reply #2 on: 13 October 2023, 07:22:42 PM »
In my experience, it's less the distance, more the type of journey that you undertake. Short journeys in a diesel provide little benefit over petrol because they don't warm up as quickly as a petrol car. So in winter, the car is colder & takes longer to defrost.

I really only got to understand the energy equations of this when I was running the 2.2TiD as a daily.

8 miles / 15 minute journey gave 28-30 mpg, which is no better than the Aero achieves. Of course, on a long journey, the economy is much better because the cold engine enrichment becomes of minimal value
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phoenix

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Re: Mileage to warrant a diesel?
« Reply #3 on: 16 October 2023, 11:21:19 AM »
Looking at it from an emissions point of view, it's a devil of a choice.

You have to buy a very modern diesel (with Adblue technology etc.) to not spew out nasty stuff which is then even more complex and liable to big repair bills.

Personally I'd prefer to stick to petrol unless I was doing more like 20k+ as whilst the CO2 emissions (and fuel costs) are higher, the other pollutants are a lot less.

Audax

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Re: Mileage to warrant a diesel?
« Reply #4 on: 17 October 2023, 09:55:12 PM »
I worked it out about 13-14 years ago now with the data we had from what we had charged customers. Based on a 9-3 diesel vs. a 9-3 petrol, you'd need to be doing 18,000 miles a year in a diesel to break even with a petrol Saab based on VED, purchase, depreciation and maintenance and fuel costs. However that was also taking into account that the equivalent car with a diesel engine cost about £3000-£4000 quid more to purchase than the equivalent petrol at the time, notably at the time it was very common for a diesel to come in for a "simple" MOT and service and leave with a £1k+ bill, that was a rare occurence with a petrol 9-3.

Steve McF

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Re: Mileage to warrant a diesel?
« Reply #5 on: 18 October 2023, 02:35:11 PM »
Interesting - the reason I ask was that I noticed that whereas some of the petrol 9-5s/9-3s beyond 2007 seemed to be £600+ road tax, the diesels seemed to be £200 or less.

But, at most, I might only be doing 8000 miles a year at the moment. I fancy the idea of a newer Saab than the one I have (even to have alongside it), but can't really justify it. I'd love an NG9-5, but most of them are diesel.

Audax

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Re: Mileage to warrant a diesel?
« Reply #6 on: 18 October 2023, 05:22:31 PM »
The VED is only a small component of car ownership that people focus on too closely quite often, there was a time when the 2.8 V6 Aero was the cheapest Saab to buy as people were put off by fuel and VED costs... which meant you could buy a V6 Turbo for around £4k as a trader and the equivalent diesel was £8k... £4000 buys you a hell of a lot of fuel and VED and given most people would only keep a car for 4 or 5 years it would cover the difference.

As was already mentioned in this thread, we had a woman come to us wanting a Saab and wanting to save money. At the time we talked to her she only drove a couple of thousand miles a year so wanted to "save money" - her typical journey was 3 miles on country roads to a train station where she'd park and 3 miles home again. I suggested she got a V6 petrol as fuel costs weren't really an issue and they were much cheaper to buy, she said that the VED was too much, petrol costs too much and she wanted a diesel, we pointed out that on short journeys a diesel really didn't make sense but she wouldn't hear it. We actually refused to sell her a diesel as we didn't want to stand the warranty on a car used like that due to the 1.9 and it's EGR+DPF problems. She went elsewhere and got herself a diesel, 3 months later she brought it to us as she was cold when driving to the station in winter as it never got hot and then a year after that it needed a large amount spent on EGR related problems and other general diesel problems, she then said "I thought a diesel would be cheaper"...

Also, the annual service on a diesel is about 20% more expensive than the equivalent petrol model and the 1.9 had crusty wiring looms 10 years ago but the petrol models seemed to be pretty solid. I just think that without there being some significant saving somewhere it doesn't make sense.

carrera

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Re: Mileage to warrant a diesel?
« Reply #7 on: 20 October 2023, 10:41:12 PM »
Interesting - the reason I ask was that I noticed that whereas some of the petrol 9-5s/9-3s beyond 2007 seemed to be £600+ road tax, the diesels seemed to be £200 or less.

The auto 9-5, registered post March 2006 are the ones with the £600+ road tax

The manual box cars are a relative bargain at £395  ::)
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