I've been keeping track of my gas mileage for a couple months now and I’m a little disappointed with the results. I drive 15 miles both ways (practically all highway) to work, and I pretty much baby my Mini. I’m averaging 26 mpg. I got my 2010 R57 with 32,000 miles on it around 3 months ago. I started doing the research and came up with the very thing my dealership is telling me. I may need the valves cleaned. They are running a special now and will walnut blast the valves and clean the injectors for right around $500. I’m a little bummed because this is a certified Mini and all they did was talk about how the car was gone over by the certified mechanics and it should have no problems.

I would have thought if this is a known problem, they would have looked into the valve problem before they certified it. So it looks like I'll take a $500 gamble and hope my gas mileage improves.

 

IMO , if walnut cleaning is not spelled out in the owners manual as a needed or required scheduled maint item then it should be covered by warranty if still under warranty.

We know this is a issue with direct injected engines BUT if the manf hides this fact and it's cost then they should be paying to fix it or SPELL it out as needed service.

What dealer ? In case my CPO ends up needing this.

 

Mini of Arlington, Texas

 

It is indeed a gamble. Carbon buildup can hurt gas mileage, but it's hard to know whether it is the actual cause in your case. Does your dealer agree that your mileage is lower than expected?

 

FYI I get about 24mpg avg but mostly city driving, when running to Dallas I get about 32-34mpg avg for that trip.

My wifes CPO has about 34Kk now and she drives to Dallas for work and gets about 30-32mpg avg and she drives spirited , got pulled over on GBH doing 93 once.

 

I'm not sure, We talked about the valve cleaning and he said I should do it..

 

then I would say where in my owners manual does it list this as a scheduled item ? If not why is it not covered by warranty.

Since that is my dealership I am really curious how this goes. Glad they aint asking $800+ dollars for it .

 

It would have to increase your MPG ALOT to get that $500 investment back. Have you tried resetting AVG MPG and just drive hwy for 10-20 miles and see what you get ? Should be 30-35mpg. I have had 38-40 myself but that's above even what sticker said it should have.

 

I’m not getting the 26 mpg from the car reading, I’m doing the math from writing down my mileage and gallons used.

 

Hi JMC1, 32000 miles isn't a lot of miles to justify getting your valves clean, If your mini is running correctly with the correct fuel air mix and doesn't have leaking valve seals there should be no way you would need your valves cleaned.


If there was a major issue with your cylinder head requiring that you remove it for repairs (blown head gasket etc) then this would be the time you would remove the valves and clean them and the lap the valves into the valve seats.


Walnut blasting isn't required, one can clean valves with a bench grinder and wire wheel. It seems to me that your dealer is trying to drum up additional work (profit margin) to me.


A member on this forum called "Corners" has some good YouTube videos under the name Mod Mini and in one of his engine rebuild videos, you can see how simple it is to remove Valves and clean and Lap them.


Whilst not everyone is confident on delving into the insides of an engine, its worth the look and if your up for it, it could save you some money long term.

 

I find that the cars computer is pretty close to actual, within 1 MPG the 3 times I checked.

 

The first question I would have would be whether the dealer has already visually inspected the engine or are they just speculating because history of others tells them that this could be because of carbon buildup?

I had my first walnut blasting done on my JCW in 2013 at 100,000. You can see from the video I included what the valves looked like before and after. I asked the vendor their thoughts and they said they had seen worse at lesser miles. So yours may not look like this.

And yes, my car ran a lot better afterward. Not MPG, but performance was great.

http://vimeo.com/65613419

 

I've seen valves needing the carbon cleaned from as low as around 12,000 miles and on up.

Using the walnut blasting method means you don't have to take the whole engine apart to put stuff on a bench grinder.

JMC1, one theory that I have seen regarding how quickly the carbon builds up is how the vehicle is driven. If it is a lot of short trips, the engine never gets up to the full operating temp for an extended time in order to help actually burn off some of the oil that is getting in there. I realize you just got the MINI, so it would be how the previous owner was using/driving it that would influence the distance and whether they are already clogged up. Considering the low mileage, unless the previous owner was only using the MINI for a few trips a year, lots of short commutes seems likely.

I have seen most people who needed the carbon cleaning at a low mileage getting it covered under warranty. I'm not sure how CPO works, but that might be a question to ask the dealer - why is it not covered by the CPO warranty. If they are not going to cover it, you might want to explore some independent shops. Most of the ones I'm familiar with have dropped the price for a walnut blasting down into the $350 range.

Going forward, I'd suggest planning for carbon cleaning as a regular maintenance item.

 

I'd push real hard for warranty coverage. My 2009 MCS needed the walnut shell treatment at about 30K miles, and it was done at no cost to me. My symptoms were a bit of hesitation / vibration you could feel in the pedal on a hard acceleration. Plus there was a misfire code stored in the system -- this might be why they covered it.

 

I agree. What the heck is the certified warranty for then? I hope my warranty covers me when this happens...

 

It's not about MPG ROI on $500 valve cleaning.
Usually, valve cleaning (walnut shell blasting is the most effective, but there are other methods) is done on the intake valves. Exhaust valves are similarly effected, but harder to get to (have to remove down-pipe and turbo/exhaust manifold).

Unfortunately, if you do NOT clean the valves, the carbon build-up will create heat-soak points on the valves and they will eventually crack and fall apart. This failure mode usually effects exhaust valves more than intake ones.

Ask me how I know *sigh*.
Just finished N14 engine swap, with the old engine loosing 1 exhaust valve on cyl 4.

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BTW, my mileage went up from ~26.5 MPG cross-commute average, to ~30.5 MPG on the same cross-commute rout (some highway, mostly back roads) after an N14 oil swap from a 56K carbon build-up incrusted engine with a hole in cyl 4 exhaust valve, to a bran new MINI N14 engine.

YMMV,
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