Issues after misfuelling 1.5 diesel

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Post by Percy247 » Tue Oct 05, 2021 5:14 pm

Good afternoon,

Manage to make the fuel crisis worse by putting 45 litres of petrol in my wife’s M2 1.5 diesel two weeks ago. Car is 16 plate and has done 60K miles. Tank was almost empty, so it cut out after 4 miles. Long story short, recovered off A1, tank symphoned and lines drained. 10 litres of diesel added and it started eventually after some horrible sounding rattles. Guy who did it said there was unlikely to be any lasting damage. Famous last words…….

Definitely seems down on power and DPF regen frequency has increased noticeably. One common thread that appears on forums is avoid the main dealer as the bill will be huge. Can anyone offer any sensible suggestions or advice on where to start.

My thoughts were;

1. Check oil level for possible dilution issues and change if high (only done 4.5k in last 9 months)
2. Replace fuel filter if I can locate it. (petrol as a solvent might have cleaned dirt out of the lines partially blocking the filter)
3. Refill tank and add injector cleaner (petrol might of cleaned these out).
4. Hope it’s not the high pressure fuel pump!

Thought I might have got away with this but it would appear not!

Thanks for reading and any replies greatly appreciated.

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Post by Percy247 » Wed Oct 06, 2021 10:13 am

Checked the oil this morning and it’s just below the “X” on the dipstick, so there would appear to be oil dilution going on. Could this be a possible causes for the slight loss of power and increased frequency of DPF regens? Never had any previous DPF issues and never seen a warning light. Either way, as a first job I will be changing the oil and filter.

I also located the fuel filter. On the Mazda 2, it’s in exactly the same place as the CX-3, buried under the car next to the fuel tank. It has a drain on the bottom and the service manual says to drain the filter yearly and replace every 3 years. Is this a water separator/sediment drain? Do I drain it until diesel comes out?

Can’t say I fancy changing the filter myself as access is a bitch without a lift. How likely is it that diesel will drain out of the fuel lines when I remove the filter? Think I might buy the filter and pay a local garage to change it after I have shown them where it is!

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Post by Percy247 » Wed Oct 06, 2021 10:03 pm

Is there anybody out there?

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Post by HouseSpider » Thu Oct 07, 2021 5:41 am

Yes, but not sure if anyone has had the same issue and therefore can't help.
Sports Nav Auto Petrol 2017, 131bhp (chipped), Soul Red, Half Stone Leather, Safety Pack, Arm Rest, Auto Folding Mirror Kit, Detachable Tow Bar, HatchBag Boot Liner, Stebel Nautilus Compact horn.

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Post by jtonline » Thu Oct 07, 2021 9:35 am

I would say draining water from the filter, or replacing it on a CX-3 is best left to a garage mechanic.
See this post on another forum: ... ter.16914/
Sept. 2015 CX-3 Sport Nav, Dynamic Blue Mica, 1.5 Diesel, AWD, Automatic
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Post by Percy247 » Fri Oct 08, 2021 7:57 pm

This is another fine example of Mazda deliberately discouraging DIY servicing through design. I have read the linked thread and wonder if the fuel filter could simply be unscrewed without having to remove the housing and fuel lines. The filter is not fluted, so an oil wrench is out of the question and access for a strap type tool would be difficult. Why did they not put the filter in the engine bay like on most cars?

I have changed the oil and filter and will keep an eye on both the oil level and DPF regen frequency. I will see if things improve. I suspect that the oil level has been rising for some time and is unrelated to the misfuelling. A lot of people recommend archoil diesel fuel treatment to clean out the turbo, dpf, injectors and egr so I am considering this as a next step.

A diesel made sense when we bought it but since COVID it no longer does.

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Post by Graeme67 » Sat Oct 09, 2021 9:32 am

It's not unique to Mazda to make things more difficult for the DIY mechanic, Most car makers are doing it, Sometimes not on purpose but with more and more equipment being installed on cars there simple is not room to fit components in the engine bay for easy access, That said they ARE making it more of a challenge to do some work yourself, Making it necessary to take the car to a mechanic or dealer (hoping you choose a dealer £££££).... Used Archoil diesel treatment in my Skoda when the turbo started clogging up and overboosting putting the car into limp mode, It didn't work for me, To be honest it made it worse.
2017 CX 3 1.5 Diesel

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Post by Percy247 » Sun Oct 10, 2021 12:38 pm

This car is starting to do my nut in. As it rarely gets above 2000 rpm, I gave it one blast this morning using all the rev range up to 70 and it pulled well. Then it immediately started a DPF regen! so I kept on driving until it had completed. There were no warning lights, no limp mode and no stored fault codes. It seems to be doing a regen about every 100-150 miles. Any ideas why this might be? The aborted regens will be causing the rising oil levels. Is there a DPF sensor that might have failed or could I be looking at injector problems?

Then the tyre pressure warning light came on! To add insult to injury I now have a puncture and I noticed that the front brake pads need changing again. I think I will try a diesel fuel additive and if there is no improvement then I will find a local diesel specialist.

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Post by AndyRen » Sun Oct 10, 2021 6:38 pm

Just sorry we can't help! Can't you get it to an independent diesel specialist?
16 plate 2L Petrol, 120bhp Soul Red Sport Nav...

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Post by Percy247 » Sun Oct 17, 2021 5:50 pm

AndyRen wrote:
Sun Oct 10, 2021 6:38 pm
Just sorry we can't help! Can't you get it to an independent diesel specialist?
No worries. I was just seeing if anyone else on here had any experience of DPF issues and maybe get an idea of how often their diesel engined cars were performing a regen. Hopefully it’s just a storm in a teacup.

After changing the oil, resetting the oil data and adding a diesel fuel additive, the car has done 165 miles on a mixture of roads without performing a regen. Average economy is showing at 80.7mpg, a figure I have not seen since the emissions software was updated by Mazda about 3 years ago. I will take it for a motorway blast this week and have been changing gear between 2500 and 3000 rpm to give the engine more of a work out and it seems happier. Does anyone know what the oil life monitor actually does? I presume it just calculates the number of regens done and then throws up the orange wrench when the oil needs changing? I can’t imagine it measuring viscosity. From now on I will be checking the oil monthly and changing it every 6 months.

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