Have chrome exhaust tips but they are always back when I wash the car. The black easily wipes off, just curious if this is normal.

I had the solid Yellow Engine light on for a day, but was told by service department could be bad gas or a loose gas cap, next day light went away, but the solid yellow light in the center speedometer is related to exhaust issues.

 

We have the same experience withe exhaust tips.

 

Normal carbon build up

 

Exhaust tip getting black deposits is normal.

Check engine light on is not. If it went away it was likely loose gas cap.

 

Thanks all.

 

I am told that an oil catch can will make some difference. The MINI engine "recycles" some of its oil-based vapor back into the intake. An oil catch can will trap some of the vapor and allow the oil to "precipitate" into the catch can before it has a chance to return to the intake. At least that's the theory...

 

I keep a towel out just for cleaning the tips on both MINIs, it comes off easy enough but you can do it every day! I have a buddy that claims the new formulations of gas is the culprit and says there a number of gas additives that can create a more complete burn of the gas and eliminate the deposits. That being said I have not tried any yet so can't say if it works or not.

 

As an old veteran MINI owner I can honestly say that MINIs have done this since they came back to the US. My 2003 Cooper and 2005 S used to get the buildup on the tailpipes. Heck even my GTi does it...

I wouldn't be surprised if my Countryman does it when it comes in too...

With the old engines the theory was that they ran rich which caused the buildup...

 

My tips seem to be really nasty after the so to Reno trek. Don't know if its the elevation or sustained hours of highway driving. It comes off easily.

 

A rag with a bit of WD-40 does a good job of cleaning off the carbon/soot...seems to deley it from reforming too...

 

i think it is just the way that the unleaded fuel (i cannot bring myself to call it gasolene) burns

my 1974 and 1987 bmw motorcycles also get the exhausts black

if i fill them with 100LL avgas, the exhausts turn a nice light tan or gray color

scott

 

I think this is a universal trait. My service advisor said these cars run rich. It helps to run 91 octane fuel. I keep a dedicated towel handy to keep them clean.

 

Low octane fuel causes the carbon build up. If you can find some Sunoco 110 octane fuel, (some independant dealers sell it) or aviation fuel, it will clean the combustion chamber through to the exhaust tips. It will be absolutely clean. Be ready to pay high bucks per gallon though.

 

So, is 93-octane (AKI) top-tier fuel considered "low octane"?

That's all I've used in my CMS and I still need to clean the tips regularly....

 

Yes, 93 octane top-tier fuel in the USA is considered low octane. Unless you try Avgas or Sunoco 110 you won't see the difference. If there is no difference and it doesn't clear up you've got bigger problems. I run 93 and 94 octane fuels and my exhaust carbon up after about 1 full tank. I run 6 to 8 gal of Sunoco 110 every 2 or 3 tanks and the carbon burns right off. What do you consider Top-tier fuel?

 

Let's see - 100LL Avgas is selling at my local GA FBO for $5.90/gal. My local Mobil station is selling 93-octane (AKI) for $3.70/gal. Based on a fill-up volume of 12 gallons, my up-charge for using 8 gallons of 100LL and 4 gallons of 93 versus the full 12 gallons of 93 is $17.60 per tank. Do this for three tanks and my up-charge is $52.80.

For that up-charge, I can opt to use 93-octane and clean my exhaust tips at each fill-up using a $20 bill, then discard it.

I have over 450,000 miles on four cars (BMW-200k, BMW-150k, MINI-100k, MINI-12k) using 93-octane and careful maintenance. So far, no ill-effects from using top-tier fuel without racing or 110-octane. In fact, one might argue that similar results could be had using top-tier gas of lesser octane (and cost).

Top Tier Gasoline


YMMV,

 

So your saying you have carbon build-up but you don"t have a problem with it !!
I was responding to those who do have a problem with it.

 

I was merely stating that, in my case, 450,000 miles using top-tier fuel has not produced any deleterious effects from carbon build-up to the four cars I mention. And, while this is an admittedly insignificant statistical population from which broader conclusions cannot be drawn, it has worked in my application. YMMV.

Therefore, in my case, the carbon build-up on the CMS exhaust tips I deem to be only a cosmetic issue. Thus, for me, the extra cost of using a fuel-based method of eliminating carbon build-up on the tips seems, IMHO, rather expensive.

However, everyone should have the right to consider this issue in the manner they wish. If they want to use any method of addressing dirty exhaust tips, whether it be through spending money on 110-octane or by keeping a microfiber towel in the way back, it's all good.

 

Envious of you guys who can readily get 93 octane. We're stuck with 91 laced with ethanol over here.

 

i was not and do not recommend using avgas in your minis

it will kill the O2 sensors and the cat too

i was commenting that unleaded fuel burns black whereas avgas in the same engine will burn tan/gray

either fuel results in some residue as a result of combustion, in this case, unleaded is black and avgas is tan/gray

scott

 

And the WD40 smells good too

 

Right you are! IIRC, isn't avgas "low" lead and not "no" lead?

In any case, I edited my last post to read "110-octane" instead of "Avgas".

Thanks for the reminder...

 

correct, 100LL avgas has lead, but it is about 1/8 as much as the older 100/130 avgas, it is still more than the old ethyl or high-test mogas had

scott

 

After years of dealing with this problem, I masked off my stainless steel Milltek exhaust tips, scuffed them up with some scotchbrite pads, and painted them with high-temperature matte black paint. I'm so glad I did.

Now, they look mean, and not "unwashed". Never have to wipe off the exhaust tips again.

 

and that is why I did this:

https://www.northamericanmotoring.co...ml#post3442429