Engine using oil but has zero hydrocarbon emissions

[9xxNick]

I have a VAG 1.8TSi engined car which is using about a litre of oil every 1,000 miles, but has just passed an MOT with zero hydrocarbon emissions. I would have expected it to be on the high side (200ppm is the limit) when using this amount of oil.

There's no obvious leak, although that's an area I'll check again of course.

So, opinions - would this amount of oil burn show up on the MOT's hydrocarbon emissions test?

[Heaveho]

Is the cat still fitted?

[9xxNick]

Yes, everything's as originally manufactured.

[stevieturbo]

9xxNick said:

So, opinions - would this amount of oil burn show up on the MOT's hydrocarbon emissions test?

Not at all. Hydrocarbons are typically unburnt fuel.

[Fastpedeller]

It could just be their equipment - I used to work in auto industry design/development and the emission equipment is calibrated daily in that environment. At the MOT station it only has to be calibrated every 6 months - and if you look..... most of the time the probes are just kicked around the floor. I had a fiesta once with Ford OHV engine (so old design) and it showed up CO as low a level as a modern car. And also a Ka (tested at a different garage) which had ZERO CO (I kid ye not)- I asked if it meant I could get free road fund license! guy operating it didn't understand my joke

[ShiningWit]

If it's using oil under normal driving conditions it may not be when just sat there idling or held at a certain stationary Rpm, it could be the turbo passing some when on boost or getting by other areas of the engine when under load.

[Sheepshanks]

I've always wondered why the HC figures vary so much from year to year.

I know it's PPM but we had one car (Honda Jazz) which was single figures one year, around 100 the next year, then a low number the following year.

I asked about it elsewhere and was told they do a very rough test first and if it passes they leave it at that.

[Heaveho]

Probably of no consolation, but other than Mercedes, I've never known any German manufacturers products not to use this amount of oil per 1k miles. Doesn't indicate anything to be wrong with it necessarily.

[kambites]

VW class one litre per 1000 miles as "normal" for their direct injection petrol engines.

[andyiley]

9xxNick said:

I have a VAG 1.8TSi engined car which is using about a litre of oil every 1,000 miles, but has just passed an MOT with zero hydrocarbon emissions. I would have expected it to be on the high side (200ppm is the limit) when using this amount of oil.

There's no obvious leak, although that's an area I'll check again of course.

So, opinions - would this amount of oil burn show up on the MOT's hydrocarbon emissions test?

In the first instance, your MOT tester is measuring UNBURNT HYDROCARBONS, therefore, if the engine is BURNING oil, that will not come into the measure for UNBURNT HYDROCARBONS.

Perfectly normal for an engine to use that amount, although as many will, as won't.

[hygt2]

Are you using the correct weight of oil? Oil also shears so oil consumption goes up with time after oil change, especially on turbocharged engine . Did you notice any changes in oil consumption immediately after an oil change to the consumption currently?