Foul smelling fuel

[ConrodWilbur]

I switched over to premium fuel (BP Ultimate Unleaded, 98 octane) from regular unleaded (91 octane), initially I saw no difference, but after about 2 days the performance increase was impressive, I'd say a 30% improvement in acceleration (from a stop) and the fuel economy has been 25% better (20L/100km to 15L/100km as measured real time in the BMW dash).

After about 2/3 weeks now the performance is still excellent, but I've noticed the exhaust smell is really bad. It doesn't smell like normal exhaust emissions, that sulphur smell of carbon and Co2, it now smells like harsh chemicals, a really eye-watering noxious radio-active chemical smell. You cant smell it for more than half a breath or you feel like you're going to choke or vomit. I cant even be near the car when its idling in the morning, it just smells so bad. Its only the smell, its not smoking more or at all, apart from a brief steam in the morning. Is this smell normal? I put liqui-moly "tappet stop noise" in the oil about a month ago too as the lifters are noisy at times, but this smell seemed to appear only after I switched fuel.

Thanks for any input, the experts on here might be able to shed some light on this.

 

[Danno]

Where are you located? No such thing as regular 91 octane in USA or Canada.
Interesting 1st post....

 

[kschachn]

Wow a 30% increase in acceleration and a 25% increase in fuel economy. Did you contact BP and tell them, because that's truly amazing.

Oh and CO2 doesn't have a smell really. But you're on the right track.

 

[ConrodWilbur]

Where are you located? No such thing as regular 91 octane in USA or Canada.
Interesting 1st post....

Australia

 

[ARCOgraphite]

In my past experience, the following is in order of possibility:

1) Leaking Head or Manifold gasket - so coolant in the combustion chamber

2) Failing Converter - usually a sulfur dioxide odor noticed whilst reversing

Finally here is one put out on a limb: Waste chemical dumping in fuel - A wonderful midnight or even midday practice to greatly reduce disposal costs and increase purse weight. Dilution is the solution to pollution!.
Ask the crop duster who "got rid of" that dirty MEK and paraffin rinse bath at 1800 ft
-
Some other members may have a few good suggestions, as you may have simply overloaded the converter with solids now that the motor is "in tune" and these may take a while to burn off - like previous leftover bit from the last bar-b-que A good Motorway run with generous throttle application for 20 mins - give or take - should cook that up nicely.

- Ken

 

[ConrodWilbur]

I know the sweet smell of coolant in the exhaust, I had a blown head gasket years ago in a Ford, it doesn't smell sweet at all. Its a very sharp smell like isopropal alcohol, but more chemically. Interesting, I ran a full bottle of rislone hyper-lube (900ml) in the crankcase for 1000km before the last oil change (about 300 km ago) so these chemicals can store up in the converter?

 

[ConrodWilbur]

I might take it for a country burn, do a couple of hundred kilometres to burn off the converter residue. Will have to wait until lockdown is over though.

 

[ARCOgraphite]

I would suggest staying away from additives. Just a find a good oil and you wont need any.

I don't think you have to go far to burn off the converter residue. a handfull of WOT high RPM romps should do it.
But if there are metal salts in the honeycomb or on the pellets they may plate out and reduce converter efficiency.

Are you really locked off the motorways? That would never be allowed in the States - Epidemic or No.

 

[ConrodWilbur]

Ok, all good points. I shall give it a few good WOTs and see what happens. Yes, we're in full lockdown, police checkpoints at most motorways and big fines for moving around without valid reasons. Doesnt seem to be making a big difference though, the infection rates keep getting worse.

 

[Kawiguy454]

The way octane is measured in AUS may not be same as states. I believe you got more power as your vehicles computer adjusted timing and other parameters to take advantage of the fuels increased anti knock rating. This is common to modern engines that call for higher octane but can tolerate lower. Your emissions system should also measure the Cat function and throw a code if it is not working correctly. unless it is older vehicle?

 

[Surestick]

Out of curiosity, has the OP ever smelled race fuel or 100LL av-gas being burned?
They have a similar and distinctive smell. Could it be that's what he's smelling and just isn't used to it? 98 is fairly high for a "regular" gas station fuel, at least in North America, so I wonder if the formulation of the 98 Octane isn't closer to a race fuel.
Of course, I wouldn't call that a "really eye-watering noxious radio-active chemical smell" but that might just be the association with positive experiences taking the edge off the smell.

 

[ARCOgraphite]

Could it be that's what he's smelling and just isn't used to it? 98 is fairly high for a "regular" gas station fuel, at least in North America, so I wonder if the formulation of the 98 Octane isn't closer to a race fuel.
....

I think down around Oceania the pumps will be labeled in RON;
not as in Stateside where we are ASTM Anti-knock index which is calculated as: [ron+mon] * 0.5.

The only thing I noticed scent wise with our unleaded E10 is in following Motorbikes, I can smell the incompletely burned Ethanol.
especially the cammed-up EVO motors with no silencers! Not a bad whiff for a motorhead.

 

[kschachn]

The only thing I noticed scent wise with our unleaded E10 is in following Motorbikes, I can smell the incompletely burned Ethanol.
especially the cammed-up EVO motors with no silencers! Not a bad whiff for a motorhead.

You're smelling some of the combustion byproducts from EtOH not uncombusted ethanol. Probably an aldehyde.

 

[Revving2Redline]

Guessing the higher octane was non ethanol too. Could fuel with ethanol go bad in a timely matter? If he is in a high humidity area its possible I guess.

 

[ARCOgraphite]

You're smelling some of the combustion byproducts from EtOH not uncombusted ethanol. Probably an aldehyde.

That makes sense, as combustion is occurring to some proper degree, maybe lambda 0.8 when they accelerate.

 

[purelux]

Where are you located? No such thing as regular 91 octane in USA or Canada.
Interesting 1st post....

You've never seen 91 octane? https://www.fueleconomy.gov/feg/octane.shtml Ethanol free around my area at various stations is all either 90 or 91.
Many car manuals will say premium 91+ or reduced performance may be experienced aka knock sensor pulls timing.

 

[Skippy722]

You've never seen 91 octane? https://www.fueleconomy.gov/feg/octane.shtml Ethanol free around my area at various stations is all either 90 or 91.
Many car manuals will say premium 91+ or reduced performance may be experienced aka knock sensor pulls timing.

I think he means that “regular” grade gas in the US and Canada is never 91 octane.