MK4 1.5 Fuel Dilution normal Levels - Oil Analysis

Technical Area Engine, Transmission, Exhaust etc
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  1. My model of MX-5 is: MK4 MX5 1.5 Se
  2. I’m based near: Bristol
  3. I’m looking for technical help or recommendations on: Oil Analysis

I’ve recently had an oil sample carried out on my new to me 2018 ND1 1.5 SE, i sent off the sample and just recieved an email back today stating that my fuel dilution was at 2.5% and was bordering on too high (this was with Millers Oil).

The car has no codes nor any regular running issues (it does run rough at idle but mazda tells me that’s normal) so i was wondering how normal is this figure, has anyone else done oil sample analysis on their NDs and do they have similar fuel dilution levels, i never got anything close on my NC.

For context the oil in my car was 0w20 Mazda Oil on 6600 miles with at least 2 hours fast b-road driving each day and many 200+ mile roadtrips.

2

Any short journey’s before you changed the oil and sent the sample off?

3

Unfortunately not, all lasting about 1 hour or more, my usual commute is a 1 hour drive on a fast A-Road so should be enough to burn off any excess I would have thought.

4

Stick a catch can in the breather system, mine pulls out a lot of fuelly-smelling junk.

Funky idle is normal - IMO idle speed is a bit low. Much smoother at ~850rpm after a remap.

5

Try some different fuel. My NC had an uneven idle, I changed from 95 ron to 97, solved. Mine had a minor remap to 180, it made sense to change fuels.

6

What grade & brand of fuel do you use in it?

7

Is the engine getting up to temperature as if you are doing long journeys that should burn off any fuel in the oil.

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8

I use Tesco momentum so it should be fine

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9

Engine always gets up to temp, I drive for at least 30 minutes after the temp guage is at the recommended level.